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  • 1.
    Alayon Glazunov, Andres
    et al.
    KTH, School of Electrical Engineering (EES). Lund University, Sweden.
    Gustafsson, Mats
    Molisch, Andreas F.
    On the Physical Limitations of the Interaction of a Spherical Aperture and a Random Field2011In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 59, no 1, p. 119-128, article id 5618544Article in journal (Refereed)
    Abstract [en]

    This paper derives physical limitations on the interactions of antennas exciting TM or TE modes (but not both) and wireless propagation channels. The derivation is based on the spherical vector wave expansion of the electromagnetic field outside a sphere circumscribing the antennas. The result is an extension of the seminal work of Chu on the classical limitations on maximum antenna gain and radiation Q. Rather than maximizing antenna gain in a single direction we obtain physical limitations on the antenna gain pattern, which is directly translated to more condensed parameters, i.e., the instantaneous effective gain G(i) and the mean effective gain G(e) if instantaneous realizations or correlation statistics of the expansion coefficients of the electromagnetic field are known, spectively. The obtained limitations are on the maximum of G(i)/Q and G(e)/Q, which establish a trade-off between link gain and Q.

  • 2.
    Alayon Glazunov, Andres
    et al.
    Lund University.
    Gustafsson, Mats
    Lund University.
    Molisch, Andreas F.
    Lund University.
    Tufvesson, Fredrik
    Lund University.
    Kristensson, Gerhard
    Lund University.
    Spherical Vector Wave Expansion of Gaussian Electromagnetic Fields for Antenna-Channel Interaction Analysis2009In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 57, no 7, p. 2055-2067Article in journal (Refereed)
    Abstract [en]

    In this paper, we introduce an approach to analyze the interaction between antennas and the propagation channel. We study both the antennas and the propagation channel by means of the spherical vector wave mode expansion of the electromagnetic field. Then we use the expansion coefficients to study some properties of general antennas in thosefields by means of the antenna scattering matrix. The focus is on the spatio-polar characterization of antennas, channels and their interactions. We provide closed form expressions for the covariance of the field multimodes as function of the power angle spectrum (PAS) and the channel cross-polarization ratio (XPR). A new interpretation of the mean effective gains (MEG) of antennas is also provided. The maximum MEG is obtained by conjugate mode matching between the antennas and the channel; we also prove the (intuitive) results that the optimum decorrelation of the antenna signals is obtained by the excitation of orthogonal spherical vector modes.

  • 3.
    Alayon Glazunov, Andres
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Prasad, Sathyaveer
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Bolin, Thomas
    Prytz, Kjell
    Impact of Scattering Within a Multipath Simulator Antenna Array on the Ricean Fading Distribution Parameters in OTA Testing2014In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 62, no 6, p. 3257-3269Article in journal (Refereed)
    Abstract [en]

    In this paper, we investigate the unwanted scattering that exists within the multipath simulator (MPS) array antennas employed in over the air (OTA) testing of mobile terminals. The impact of scattering is evaluated in terms of the measurement uncertainty of the average received power and the Ricean K-factor. The maximum ratio combining diversity is investigated for a generic device under test comprising two half-wavelength dipole antennas. We provide closed-form expressions for the uncertainties of the average received power and the Ricean K-factor for a uniform circular array of MPS antennas and a 2-D uniformly distributed angle-of-arrival spectrum. We also derive the maximum number of MPS antennas and the minimum ring radius of the MPS system as a function of the separation between the most distant antenna elements if the device under test employs a uniform linear array. As a result, we provide design guidelines for MPS array in terms of the number antennas, the radius of the MPS array and the wavelength of the carrier frequency.

  • 4.
    Alex-Amor, Antonio
    et al.
    Univ CEU San Pablo, Informat Technol Dept, Madrid 28668, Spain..
    Palomares-Caballero, Angel
    Telemat & Comunicac Univ Granada, Dept Teoria Senal Telemat & Comunicac, Granada 18071, Spain..
    Mesa, Francisco
    Univ Seville, Dept Appl Phys 1, Escuela Tecn Super Ingn Informat, Seville 41012, Spain..
    Quevedo-Teruel, Oscar
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Padilla, Pablo
    Telemat & Comunicac Univ Granada, Dept Teoria Senal Telemat & Comunicac, Granada 18071, Spain..
    Dispersion Analysis of Periodic Structures in Anisotropic Media: Application to Liquid Crystals2022In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 70, no 4, p. 2811-2821Article in journal (Refereed)
    Abstract [en]

    This article presents an efficient method to compute the dispersion diagram of periodic and uniform structures with generic anisotropic media. The method takes advantage of the ability of full-wave commercial simulators to deal with finite structures having anisotropic media. In particular, the proposed method extends the possibilities of commercial eigenmode solvers in the following ways: 1) anisotropic materials with nondiagonal permittivity and permeability tensors can be analyzed; 2) the attenuation constant can easily be computed in both propagating and stopband regions, and lossy materials can be included in the simulation; and 3) unbounded and radiating structures, such as leaky-wave antennas (LWAs), can be treated. The latter feature may be considered the most remarkable since the structures must be forcefully bounded with electric/magnetic walls in the eigensolvers of most commercial simulators. In this work, the proposed method is particularized for the study of liquid crystals (LCs) in microwave and antenna devices. Thus, the dispersion properties of a great variety of LC-based configurations are analyzed, from canonical structures, such as waveguide and microstrip, to complex reconfigurable phase shifters in ridge gap-waveguide technology and LWAs. Our results have been validated with previously reported works in the literature and with commercial software CST and HFSS.

  • 5. Bantavis, P. I.
    et al.
    Kolitsidas, Christos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Empliouk, T.
    Le Roy, M.
    Jonsson, B. Lars G.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Kyriacou, G. A.
    A Cost-Effective Wideband Switched Beam Antenna System for a Small Cell Base Station2018In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 66, no 12, p. 6851-6861, article id 8485638Article in journal (Refereed)
    Abstract [en]

    A wideband switched beam antenna array system operating from 2 to 5 GHz is presented. It is comprised of a 4 × 1 Vivaldi antenna elements and a 4 × 4 Butler matrix beamformer driven by a digitally controlled double-pole four-throw RF switch. The Butler matrix is implemented on a multilayer structure, using 90° hybrid couplers and 45° phase shifters. For the design of the coupler and phase shifter, we propose a unified methodology applied, but not limited, to elliptically shaped geometries. The multilayer realization enables us to avoid microstrip crossing and supports wideband operation of the beamforming network. To realize the Butler matrix, we introduce a step-by-step and stage-by-stage design methodology that enables accurate balance of the output weights at the antenna ports to achieve a stable beamforming performance. In this paper, we use a Vivaldi antenna element in a linear four-element array, since such element supports wideband and wide-scan angle operation. A soft condition in the form of corrugations is implemented around the periphery of the array, in order to reduce the edge effects. This technique improved the gain, the sidelobes, and helped to obtain back radiation suppression. Finally, impedance loading was also utilized in the two edge elements of the array to improve the active impedance. The proposed system of the Butler matrix in conjunction with the constructed array can be utilized as a common RF front end in a wideband air interface for a small cell 5G application and beyond as it is capable to simultaneously cover all the commercial bands from 2 to 5 GHz.

  • 6. Bosiljevac, Marko
    et al.
    Persson, Patrik
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Sipus, Zvonimir
    Efficient Analysis of Aperture Antennas on Generally Shaped Convex Multilayered Surfaces Using a Hybrid SD-UTD Method2009In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 57, no 5, p. 1420-1431Article in journal (Refereed)
    Abstract [en]

    A novel hybrid method is described for analyzing convex multilayered conformal array antennas. The hybrid method is based on the spectral domain approach in combination with the ray-based uniform theory of diffraction (UTD) method. The analysis is divided in two parts. First, the spectral domain approach is accelerated by using an asymptotic extraction technique where the extracted term of the Green's function is calculated using UTD. It is shown that this new approach results in significant acceleration of the existing spectral domain algorithm without losing accuracy. The modified spectral domain method is then used in the second part where generally shaped convex multilayered surfaces are analyzed by using sets of canonically shaped surfaces (spheres and/or circular cylinders). Their radii are obtained using the UTD formulation, which contains important information such as distance and curvature of the generally shaped surface along each geodesic. The results obtained using the new algorithm are compared to the available results (calculated and measured) for different conformal antennas, showing very good agreement.

  • 7. Braun, Christian
    et al.
    Engblom, Gunnar
    Beckman, Claes
    Allgon System AB, Sweden.
    Evaluation of antenna diversity performance for mobile handsets using 3-D measurement data1999In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 47, no 11, p. 1736-1738Article in journal (Refereed)
    Abstract [en]

    An evaluation of two-branch antenna diversity on mobile telephones is performed in the presence of head and hand phantoms to model the influence of the user. Two mobile telephone prototypes for the 1800-MHz band are considered. The evaluation is done by measuring the three-dimensional (3-D) complex radiation patterns from each antenna with the prototypes positioned near the phantom head and hand (i.e., in talk position) and calculating the diversity performance for three different scenarios of the incoming field. The two-branch antenna setups on both prototypes produce a calculated diversity gain of about 9 dB for selection diversity at the 99% reliability level.

  • 8.
    Castillo Tapia, Pilar
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Zetterström, Oskar
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Algaba-Brazalez, Astrid
    Ericsson AB, Ericsson Res, S-41756 Gothenburg, Sweden..
    Manholm, Lars
    Ericsson AB, Ericsson Res, S-41756 Gothenburg, Sweden..
    Johansson, Martin
    Ericsson AB, Ericsson Res, S-41756 Gothenburg, Sweden..
    Fonseca, Nelson J. G.
    European Space Agcy, Antenna & Submillimetre Waves Sect, NL-2200 AG Noordwijk, Netherlands..
    Quevedo-Teruel, Oscar
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Two-Dimensional Beam Steering Using a Stacked Modulated Geodesic Luneburg Lens Array Antenna for 5G and Beyond2023In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 71, no 1, p. 487-496Article in journal (Refereed)
    Abstract [en]

    Antennas for future communication systems are required to be highly directive and steerable to compensate for the high path loss in the millimeter-wave band. In this work, we propose a linear array of modulated geodesic Luneburg lens (the so-called water drop lens) antennas operating at 56-62 GHz. The lens array antenna features 2-D beam scanning with low structural complexity. The lenses are fully metallic and implemented in parallel plate waveguides (PPWs), meaning that they are highly efficient. Each lens is fed with 13 rectangular waveguides surrounded by glide-symmetric holes to suppress leakage. The lenses provide 110? beam coverage in the H-plane with scan losses below 1 dB. In order to scan in the E-plane, we use a feeding network based on a 1:4 power divider and three phase shifters. In this configuration, the array can scan 60? in the E-plane, albeit with higher scanning losses than in the H-plane. The lens array is manufactured and a good agreement between simulated and experimental results is obtained.

  • 9.
    Chen, Ming Zheng
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering and Fusion Science.
    Mesa, Francisco
    Univ Seville, Dept Appl Phys 1, ETS Ingn Informat, Seville 41012, Spain..
    Quevedo-Teruel, Oscar
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering and Fusion Science.
    Geodesic H-Plane Horn Antennas2023In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 71, no 8, p. 6329-6339Article in journal (Refereed)
    Abstract [en]

    This article describes a detailed procedure that allows for a time-efficient design of fully metallic geodesic H-plane horn antennas using an in-house ray-tracing method together with an optimization algorithm. With all the propagation in the air, geodesic H-plane horn antennas are of low loss and highly efficient. The proposed geodesic H-plane horn antennas provide a new degree of freedom, the height profile, to alleviate phase errors, realizing high gains and aperture efficiencies. Optimizations are implemented to design the height profile for a given target, enabled by the highly accurate and time-efficient in-house ray-tracing model. To demonstrate the correctness and versatility of the proposed design procedure, two prototypes are manufactured with computerized numerical control (CNC) machining and compared to their planar counterparts, with the aim of a high increased gain and aperture efficiency, respectively. The prototypes maintain good frequency stability from 26 to 33GHz, with sidelobe levels lower than -15dB and return loss better than 15dB. The first prototype improves the realized gain by over 5dB compared to the reference horn, while the second prototype achieves an aperture efficiency of around 65% within the operating frequency band.

  • 10.
    Chen, Qiao
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering. Southeast Univ, State Key Lab Millimeter Waves, Nanjing 210096, Peoples R China..
    Mesa, Francisco
    Univ Seville, Dept Appl Phys 1, ETS Ingn Informat, Seville 41012, Spain..
    Padilla, Pablo
    Univ Granada, Dept Teoria Senal Telemat & Comunicac, Granada 18071, Spain..
    Yin, Xiaoxing
    Southeast Univ, State Key Lab Millimeter Waves, Nanjing 210096, Peoples R China..
    Quevedo-Teruel, Oscar
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Efficient Leaky-Lens Antenna at 60 GHz Based on a Substrate-Integrated-Holey Metasurface2020In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 68, no 12, p. 7777-7784Article in journal (Refereed)
    Abstract [en]

    We propose a low-cost implementation of a low-dispersive leaky-wave antenna (LWA) at 60 GHz for point-to-point 5G communications. The LWA is implemented with glide-symmetric holes in gap-waveguide technology. The radiation is produced through a slit and controlled with glide-symmetric holes. The low dispersion is achieved thanks to the use of a dispersive prism that compensates the frequency dependence of the radiation through the slit. The main innovation of our proposed design is the use of substrate integrated holes (SIHs) to implement the dispersive prism. This implementation significantly enhances the bandwidth and improves the robustness to manufacturing tolerances. Also, this implementation reduces the cost of the antenna while maintaining low losses since the majority of the propagation inside the prism is in air. Additionally, we demonstrate that the use of glide-symmetric holes in the slit allows for a better control of the amount of radiation (attenuation constant) when compared with conventional holes. The differences in the attenuation constant between conventional and glide-symmetric holes have been studied with a multimodal analysis. Apart from giving a convenient physical insight, this method also expedites the design process.

  • 11.
    Chen, Qiao
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering. Southeast Univ, State Key Lab Millimeter Waves, Nanjing 210096, Peoples R China.
    Zetterström, Oskar
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering.
    Pucci, Elena
    Ericsson AB, Syst & Technol, S-16440 Stockholm, Sweden..
    Palomares-Caballero, Angel
    Univ Granada, Dept Teoria Senal Telemat & Comunicac, E-18001 Granada, Spain..
    Padilla, Pablo
    Univ Granada, Dept Teoria Senal Telemat & Comunicac, E-18001 Granada, Spain..
    Quevedo-Teruel, Oscar
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Glide-Symmetric Holey Leaky-Wave Antenna With Low Dispersion for 60 GHz Point-to-Point Communications2020In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 68, no 3, p. 1925-1936Article in journal (Refereed)
    Abstract [en]

    In this article, two novel efficient leaky-wave antennas (LWAs) with stable radiation patterns operating in the 60 GHz band are proposed. The LWAs are implemented in groove-gap waveguide (GGW) technology. To mitigate the beam squint due to the dispersive nature of LWAs, complementary-dispersive prisms are coupled to the LWA radiation aperture. The antennas are implemented in fully metallic purely holey periodic structures, resulting in a more cost-effective and robust manufacturing process compared to previously reported pin-based structures. Two prisms are proposed, one with mirror symmetry and one with glide symmetry. When the prism possesses a glide symmetry, much fewer holes are required while maintaining a similar performance, which even further decreases the fabrication costs. The complex propagation constant is optimized for low sidelobe levels (SLLs) with tailored hole diameters and waveguide dimensions, thus for the first time demonstrating the capability of using glide-symmetric holes to control the leakage rate. Two prototypes with mirror- and glide-symmetric prisms are theoretically synthesized and validated by the simulated and experimental results. A frequency bandwidth of 11% is achieved for both prototypes with the beam squint within +/- 0.9 degrees (mirror) and +/- 1.7 degrees (glide), SLLs below -15 dB (mirror) and -13 dB (glide), total efficiency almost 90%, and realized gain of 17 +/- 0.5 dB at a fixed observing angle. The developed antennas are intended for mm-wave point-to-point communications.

  • 12.
    Dahlberg, Oskar
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Pucci, Elena
    Ericsson AB, Syst & Technol, S-16480 Stockholm, Sweden..
    Padilla, Pablo
    Univ Granada, Dept Teoria Senal Telemat & Comunicac, E-18071 Granada, Spain..
    Wang, Lei
    Hamburg Univ Technol, Inst Theoret Elektrotech, D-21079 Hamburg, Germany..
    Quevedo-Teruel, Oscar
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Low-Dispersive Leaky-Wave Antennas for mmWave Point-to-Point High-Throughput Communications2020In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 68, no 3, p. 1322-1331Article in journal (Refereed)
    Abstract [en]

    In this article, we present two efficient leaky-wave antennas (LWAs) with stable radiation pattern, operating at 60 GHz. Both antennas exhibit attractive properties such as significantly reduced beam-squint, low loss, low sidelobes, high directivity, and simple manufacturing. The beam-squint of conventional LWAs is reduced by refracting the leaked waves in a dispersive lens and the low sidelobe levels are achieved by tapering the leakage rate along the aperture. Since the antennas are implemented in groove gap waveguide technology, the losses are low. The two antennas are different in terms of their asymmetric/symmetric leakage tapering with respect to the broadside direction. Both designs are optimized for low sidelobes, but since symmetry is enforced in one, the resulting performance in terms of sidelobes is suboptimal. However, in the symmetric design, multiple stable beams can be obtained, simultaneously or independently. Twenty percent bandwidth is obtained with less than +/- 0.5 degrees beam-squint. In this frequency range, the gain is stable at 17 and 15 dBi for the asymmetric and symmetric designs, respectively. The designs are intended for point-to-point links in mmWave communication networks where low losses, directive beams, and low sidelobes are expected to be key features.

  • 13.
    Ebrahimpouri, Mahsa
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Quevedo-Teruel, Oscar
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Bespoke Lenses Based on Quasi-Conformal Transformation Optics Technique2017In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 65, no 5, p. 2256-2264Article in journal (Refereed)
    Abstract [en]

    In this paper, a systematic method to design a quasioptimum lens profile based on quasi-conformal transformation optics technique for a given excitation is presented. This method is applied to a number of conventional antennas, such as an aperture and a log-spiral slot. In all these configurations, an increase of the directivity is observed. Furthermore, using this method, a quasi-optimum graded index lens for a broadband enhanced leaky slot excitation is designed and the results are compared with a hyperhemispherical lens with and without matching layers. Our proposed methodology demonstrates to be able to increase the directivity, to reduce the sidelobes and the cross polarization in a broad bandwidth from 20 to 70 GHz. Due to the continuously changed dielectric constant of the lens profile, reflections are also reduced considerably inside the lens.

  • 14.
    Ellgardt, Anders
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    A Scan Blindness Model for Single-Polarized Tapered-Slot Arrays in Triangular Grids2008In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 56, no 9, p. 2937-2942Article in journal (Refereed)
    Abstract [en]

    A simple model is presented that predicts scan blindness in the E-plane for single polarized tapered-slot arrays where the elements are positioned in a triangular grid. The blindness occurs when the phase progression along the dielectric substrates is equal to the phase progression of a leaky mode in the structure. A simple equation is presented that estimates the frequency at which the scan blindness occurs for a given angle in the E-plane. This equation is derived from a simple representation of the phased array antenna, but includes the dominant effect of this particular class of scan blindness. The method is shown to agree well with computed results obtained with two different numerical codes.

  • 15.
    Ellgardt, Anders
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Wikström, Andreas
    A single polarized triangular grid tapered-slot array antenna2009In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 57, no 9, p. 2599-2607Article in journal (Refereed)
    Abstract [en]

    A triangular grid single polarized tapered-slot array antenna for radar applications is studied. Compared with a rectangular grid an equilateral triangular grid allows a larger unit cell without any onset of grating lobes. Since single polarized tapered-slots in triangular grids support guided modes, which cause scan blindness, the increase in unit cell size is smaller than the optimal 15%. The design presented in the paper is capable of scan angles out to 60° from broadside in the E and H planes. To improve the match over the radar band a local minimum in the active reflection coefficient is positioned at the most critical scan direction, resulting in a reflection coefficient that is less than -12 dB in the X-band. To reduce the radar cross section for the cross-polarization an absorbing layer is positioned above the ground plane, which affects some of the guided modes that lead to scan blindnesses. An experimental antenna with 16×16 elements was built, and it was found that the H-plane performance for large scan angles for the finite antenna deviates more than expected from the infinite array approximation. Otherwise both mutual coupling measurements and embedded element patterns agrees well with the numerical results.

  • 16. Emadeddin, Ahmad
    A compact ultra-wideband multibeam antenna system2018In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 66, p. 125-131Article, review/survey (Refereed)
  • 17. Emadeddin, Ahmad
    A Parallel Plate Ultrawideband Multibeam Microwave Lens Antenna2018In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 66, p. 4878-4883Article, review/survey (Refereed)
  • 18.
    Emadeddin, Ahmad
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering and Fusion Science.
    Jonsson, B. Lars G.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering and Fusion Science.
    Wide Scan, Active K-Band, Direct-Integrated Phased Array for Efficient High-Power Tx-Generation2023In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 71, no 9, p. 7579-7584Article in journal (Refereed)
    Abstract [en]

    In this communication, we propose a new wide-scan active direct-integrated 1×5 phased array antenna (AIPAA) for mm-Wave applications. The AIPAA's unit-cell comprises three K-band miniaturized tapered slot elements, a GaN high electron mobility transistor (HEMT) as a power amplifier (PA), a stability circuit, an input matching network (M.N.), and biasing components. The tapered slot antenna element is reshaped so that its input impedance closely matches the optimal load impedance of the HEMT (Zopt = 6 + j38 Ω at 22 GHz), which enhances the system efficiency. The peak-integrated PAs' power-added efficiency (PAEp) is ≥ 56 % with ≤ 9% variation over scan coverage (g±50°) at 1.5 dB power backoff from P1dB. The peak AIPAA system power-added efficiency (PAEs) is 51% with a peak array radiation efficiency of 92%. The relative frequency bandwidth with PAEp above 25% is between 9% and 13% over the scan range. The proposed AIPAA demonstrates less than 0.9 and 1 dB scanloss over the scan coverage in terms of antenna array gain and PAs' power gain (Gp), respectively. The peak PA-integrated array gain and EIRP at P1dB of 24 dBi and 51 dBm are achieved, respectively. The proposed AIPAA's size is 18 × 58 × 17 mm3 with a cell of 9.2 × 6.5 × 1.8 mm3. The measurements are in good agreement with electromagnetic and circuit co-simulation results.

  • 19.
    Escobar, Ana C.
    et al.
    Universidad Nacional de Colombia, Department of Physics, Bogota, Colombia.
    Mesa, Francisco
    Universidad de Sevilla, E.T.S. de Ingeniería Informática, Departamento de Física Aplicada 1, Seville, Spain.
    Quevedo-Teruel, Oscar
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Baena, Juan D.
    Universidad Nacional de Colombia, Department of Physics, Bogota, Colombia.
    Homogenization of Periodic Structures Using the Multimodal Transfer Matrix Method2023In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 71, no 6, p. 4976-4989Article in journal (Refereed)
    Abstract [en]

    This work presents a method for obtaining the constitutive parameters of periodic structures from the computation of their dispersion relation and average fields. The method uses the scattering parameters (S-parameters) of multiple Bloch modes of a single unit cell. The corresponding multimodal scattering matrix is obtained with a suitable general-purpose electromagnetic software. Further post-processing of this scattering matrix is then carried out, which allows for the computation of the dispersion relation of structures with realistic finite conductivity or made of lossy dielectrics, as well as the calculation of the attenuation constant and the retrieval of the impedance, permittivity, and permeability. The proposed method is applied to homogenize some systems of interest: an artificial electric plasma built with wires, a free-space matched left-handed metamaterial based on two laterally shifted split ring resonators, a high-permittivity artificial dielectric based on densely arranged square metal patches, and a μ -near-zero metamaterial made of metallic cubes embedded in a dielectric. The retrieved material parameters are found to accurately describe the scattering of finite samples of the corresponding homogenized structures. This research is limited to orthorhombic unit cells smaller than half the free-space wavelength to avoid diffracted beams. Besides, since only one propagation direction is considered, only the transverse components of constitutive parameters are retrieved.

  • 20.
    Fonseca, Nelson J. G.
    et al.
    European Space Agcy, Antenna & Submillimeter Waves Sect, NL-2200 AG Noordwijk, Netherlands..
    Liao, Qingbi
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Quevedo-Teruel, Oscar
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Equivalent Planar Lens Ray-Tracing Model to Design Modulated Geodesic Lenses Using Non-Euclidean Transformation Optics2020In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 68, no 5, p. 3410-3422Article in journal (Refereed)
    Abstract [en]

    This article describes a design procedure that enables a time-efficient evaluation of the focusing properties of modulated geodesic lenses using ray tracing on the equivalent gradient-index planar lens. The method uses transformation optics to define the equivalent planar relative permittivity distribution of axially symmetric surfaces and a ray-tracing model to evaluate the phase distribution in the aperture of the lens. This approach is of interest to optimize modulated geodesic lenses having polynomial profiles, reducing their height while preserving their wideband behavior and wide angular focusing properties. The approach is validated with a specific lens design. The profile is optimized at 30 GHz, while the focusing properties are monitored over the complete Ka up-link frequency band allocated to satellite communications (i.e., 27.5 & x2013;31 GHz). The manufactured prototype produces 21 beams equally spaced every 7.5 & x00B0; over the extended angular range of & x00B1;75 & x00B0;. The ray-tracing model results are compared in detail with the corresponding full-wave model results and experimental data. The manufactured design has return loss better than 15 dB over a fractional frequency bandwidth larger than 30 & x0025;, in line with the predictions. Excellent scanning properties are demonstrated over an angular range of & x00B1;60 & x00B0; with scan losses below 1 dB and good pattern stability, including on sidelobe levels. A height reduction by a factor of 4, when compared to a conventional geodesic lens, is demonstrated with this specific design.

  • 21.
    Frid, Henrik
    et al.
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Holter, Henrik
    Jonsson, B. Lars G.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    An Approximate Method for Calculating the Near-Field Mutual Coupling Between Line-of-Sight Antennas on Vehicles2015In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 63, no 9, p. 4132-4138Article in journal (Refereed)
    Abstract [en]

    Calculating the mutual coupling between antennas on vehicles using full-wave simulations requires a vast amount of computer resources due to the electrical size of the structures. We therefore propose an alternative and approximate method to determine mutual coupling between antennas on vehicles for the case where there is line-of-sight (LOS) between the antennas. The proposed method is based on approximating the mutual coupling between LOS antennas on vehicles as near-field transmission between antennas in free space. We begin the analysis with a brief review of four methods for calculating the near-field free-space transmission. Of the investigated methods, we demonstrate that a nonsingular form of the near-field transmission integral originally proposed by Yaghjian (1982) is the most suitable for LOS antennas on vehicles. We introduce a modification to this method, in order to only use the antenna far-fields and geometrical separation to determine the mutual coupling. The comparison with full-wave simulations indicates that the proposed method has a good accuracy for LOS antennas. This paper ends with a full-scale mutual coupling calculation for two monopoles on an aircraft under LOS conditions, demonstrating a root mean square (rms) accuracy of 6 dB for frequencies up to 5 GHz, as compared with full-wave simulations.

  • 22.
    Giusti, Federico
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Chen, Qiao
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Mesa, Francisco
    Univ Seville, ETS Ingn Informat, Dept Appl Phys 1, Seville 41004, Spain..
    Albani, Matteo
    Univ Siena, Dept Informat Engn & Math, I-53100 Siena, Italy..
    Quevedo-Teruel, Oscar
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Efficient Bloch Analysis of General Periodic Structures With a Linearized Multimodal Transfer-Matrix Approach2022In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 70, no 7, p. 5555-5562Article in journal (Refereed)
    Abstract [en]

    A systematic and efficient multimodal transfer-matrix approach is proposed for the comprehensive Bloch analysis of general 1-D/2-D/3-D periodic structures. We provide a linearization procedure for transforming the original nonlinear eigenvalue problem associated with 2-D/3-D structures to a standard one that can easily be solved without the need of a zero-searching algorithm in the complex plane. The proposed approach has been validated with bounded/open structures with complex geometries and/or inhomogeneous lossless/lossy materials. It demonstrates a significantly reduced computational time and leverages the strengths of full-wave simulators to deal with general problems and ad hoc quasi-analytical methods to give a fundamental understanding of the behavior of the structure. Also, it allows for an accurate evaluation of the imaginary part of the wavenumber, which offers information of material dissipation, stopband rejection, leakage, and complex modes.

  • 23.
    Gomez-Torrent, Adrian
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Micro and Nanosystems.
    García-Vigueras, María
    Institut National des Sciences Appliquées de Rennes: Rennes, Bretagne, FR.
    Le Coq, Laurent
    Université de Rennes 1: Rennes, Bretagne, FR.
    Mahmoud, Adham
    Ettorre, Mauro
    CNRS Délégation Bretagne et Pays de Loire: Rennes, Bretagne, FR.
    Sauleau, Ronan
    Université de Rennes 1: Rennes, FR.
    Oberhammer, Joachim
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Micro and Nanosystems.
    A Low-Profile and High-Gain Frequency Beam Steering Subterahertz Antenna Enabled by Silicon Micromachining2020In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 68, no 2, p. 672-682Article in journal (Refereed)
    Abstract [en]

    A very low-profile sub-THz high-gain frequencybeam steering antenna, enabled by silicon micromachining, is reported for the first time in this paper. The operation bandwidth of the antenna spans from 220 GHz to 300 GHz providing a simulated field of view of 56°. The design is based on a dielectric filled parallel-plate waveguide (PPW) leaky-wave antenna fed by a pillbox. The pillbox, a two-level PPW structure, has an integrated parabolic reflector to generate a planar wave front. The device is enabled by two extreme aspect ratio, 16 mm x16 mm large perforated membranes, which are only 30 μm thick, that provide the coupling between the two PPWs and form the LWA. The micromachined low-loss PPW structure results in a measured average radiation efficiency of −1 dB and a maximum gain of 28.5 dBi with an input reflection coefficient below −10 dB. The overall frequency beam steering frontend is extremely compact (24mm x 24mm x 0.9 mm) and can be directly mounted on a standard WM-864 waveguide flange. The design and fabrication challenges of such high performance antenna in the sub-THz frequency range are described and the measurement results of two fabricated prototypes are reported and discussed.

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  • 24.
    Gomez-Torrent, Adrian
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Micro and Nanosystems.
    Tomura, Takashi
    Kuramoto, Wataru
    Hirokawa, Jiro
    Watanabe, Issei
    Kasamatsu, Akifumi
    Oberhammer, Joachim
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Micro and Nanosystems.
    A 38 dBi Gain, Low-Loss, Flat Array Antenna for 320 GHz to 400 GHz Enabled by Silicon-On-Insulator Micromachining2020In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 68, no 6, p. 4450-4458Article in journal (Refereed)
    Abstract [en]

    Two high-gain flat array antenna designs operatingin the 320 – 400 GHz frequency range are reported in this paper. The two antennas show measured gains of 32.8 dBi and 38 dBi and consist of a 16x16 (256) element array and a 32x32 (1024) element array, respectively, which are fed by a corporate H-tree beamforming network. The measured operation bandwidth for both antennas is 80 GHz (22% fractional bandwidth), and the total measured efficiency is above −2.5 dB and above −3.5 dB forthe two designs in the whole bandwidth. The low measured loss and large bandwidth are enabled by optimizing the designs to the process requirements of the SOI micromachining technology used in this work. The total height of the antennas is 1.1mm (1.2 at the center frequency), with sizes of 15mm x 18mm and 27mm x 30mm for both arrays. The antennas are designed to be directly mounted onto a standard WM-570 waveguide flange.The design, fabrication, and measurements of eight prototypes are discussed in this paper and the performance of the antennas compared to the simulated data, as well as manufacturability and fabrication repeatability are reported in detail.

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  • 25. Gustafsson, Mats
    et al.
    Cismasu, Marius
    Jonsson, B. Lars G.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Physical Bounds and Optimal Currents on Antennas2012In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 60, no 6, p. 2672-2681Article in journal (Refereed)
    Abstract [en]

    Physical bounds on the directivity Q-factor quotient and optimal current distributions are determined for antennas of arbitrary shape and size using an optimization formulation. A variational approach offers closed form solutions for small antennas expressed in the polarizability of the antenna structure. Finite sized antennas are solved using Lagrangian parameters in a method of moments formulation. It is also shown that the optimal charge density for a small antenna can be generated by several current densities. Numerical examples for small and large antennas are used to illustrate the results.

  • 26. Gustafsson, Mats
    et al.
    Jonsson, B. Lars G.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Antenna Q and Stored Energy Expressed in the Fields, Currents, and Input Impedance2015In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 63, no 1, p. 240-249Article in journal (Refereed)
    Abstract [en]

    Although the stored energy of an antenna is instrumental in the evaluation of antenna Q and the associated physical bounds, it is difficult to strictly define stored energy. Classically, the stored energy is either determined from the input impedance of the antenna or the electromagnetic fields around the antenna. The new energy expressions proposed by Vandenbosch express the stored energy in the current densities in the antenna structure. These expressions are equal to the stored energy defined from the difference between the energy density and the far field energy for many but not all cases. Here, the different approaches to determine the stored energy are compared for dipole, loop, inverted L-antennas, and bow-tie antennas. We use Brune synthesized circuit models to determine the stored energy from the input impedance. We also compare the results with differentiation of the input impedance and the obtained bandwidth. The results indicate that the stored energy in the fields, currents, and circuit models agree well for small antennas. For higher frequencies, the stored energy expressed in the currents agrees with the stored energy determined from Brune synthesized circuit models whereas the stored energy approximated by differentiation of input impedance gives a lower value for some cases. The corresponding results for the bandwidth suggest that the inverse proportionality between the fractional bandwidth and Q-factor depends on the threshold level of the reflection coefficient.

  • 27.
    He, Wang
    et al.
    Zhejiang Univ, Coll Opt Sci & Engn, Ctr Opt & Elect Res, Hangzhou 310058, Peoples R China..
    Xu, Bo
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering. Ericsson Res, Ericsson AB, SE-16480 Stockholm, Sweden..
    Scialacqua, Lucia
    Microwave Vis Grp, I-00071 Pomezia, Italy..
    Ying, Zhinong
    Sony Corp, Sony Res Ctr, SE-22188 Lund, Sweden.;Aalborg Univ, Propagat & Mm Wave Sect APMS, Dept Elect Syst, DK-9220 Aalborg, Denmark..
    Scannavini, Alessandro
    Microwave Vis Grp, I-00071 Pomezia, Italy..
    Foged, Lars Jacob
    Microwave Vis Grp, I-00071 Pomezia, Italy..
    Zhao, Kun
    Sony Corp, Sony Res Ctr, SE-22188 Lund, Sweden.;Aalborg Univ, Propagat & Mm Wave Sect APMS, Dept Elect Syst, DK-9220 Aalborg, Denmark..
    Di Paola, Carla
    Aalborg Univ, Propagat & Mm Wave Sect APMS, Dept Elect Syst, DK-9220 Aalborg, Denmark..
    Zhang, Shuai
    He, Sailing
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering. Zhejiang Univ, Coll Opt Sci & Engn, Ctr Opt & Elect Res, Hangzhou 310058, Peoples R China..
    Fast Power Density Assessment of 5G Mobile Handset Using Equivalent Currents Method2021In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 69, no 10, p. 6857-6869Article in journal (Refereed)
    Abstract [en]

    As the fifth-generation (5G) mobile communication is utilizing millimeter-wave (mmWave) frequency bands, electromagnetic field (EMF) exposure emitted from a 5G mmWave mobile handset should be evaluated and compliant with the relevant EMF exposure limits in terms of peak spatial-average incident power density (PD). In this work, a fast PD assessment method for a 5G mmWave mobile handset using the equivalent current (EQC) method is proposed. The EQC method utilizes the intermediate-field (IF) data collected by a spherical measurement system to reconstruct the EQCs over a reconstruction surface and then computes the PD in close proximity of the mobile handset with acceptable accuracy. The performance of the proposed method is evaluated using a mmWave mobile handset mock-up equipped with four quasi-Yagi antennas. The assessed PD results are compared with those computed using full-wave simulations and also those measured with a planar near-field (NF) scanning system. In addition, three influencing factors related to the accuracy of the EQC method, namely, the angular resolution, the phase error, and the handset position in the IF measurements, are also analyzed. The proposed method is a good candidate for fast PD assessment of EMF exposure compliance testing in the mmWave frequency range.

  • 28.
    Jonsson, B. Lars G.
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Ferrero, Fabien
    Univ Cote dAzur, Natl Ctr Sci Res CNRS, Lab Elect Antennes & Telecommun LEAT, F-06903 Sophia Antipolis, France..
    Shi, Shuai
    Ericsson AB, SE-16480 Stockholm, Sweden..
    Wang, Lei
    Heriot Watt Univ, Sch Engn & Phys Sci, Inst Sensors Signals & Syst, Edinburgh EH14 4AS, Midlothian, Scotland..
    Optimal Bandwidth Positions for a Terminal Embedded Antenna: Physical Bounds and Antenna Design2021In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 69, no 4, p. 1931-1941Article in journal (Refereed)
    Abstract [en]

    This article considers a small embedded planar antenna in a square-shaped terminal of 25 cm(2) at a frequency band near 900 MHz, intended for long-range communication. This article aims to shows how the Q-factor bounds can be used to predict the performance of such an antenna. Both to determine the optimal bandwidth and the variations in the total efficiency but also to help to inspire the antenna design shape. The choice of shape and position impacts both bandwidth and efficiency. The latter is illustrated by a center-edge positioned folded inverted F-antenna with higher efficiency, as compared to, a more bandwidth optimal meander antenna at the corner. Fabrication and measurements show that the corner positioned antenna is close to bandwidth optimal, and also that it and the associated optimal current have a similar radiation pattern.

  • 29.
    Jonsson, B. Lars G.
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Shi, Shuai
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Wang, Lei
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Ferrero, Fabien
    Lizzi, Leonardo
    On Methods to Determine Bounds on the Q-Factor for a Given Directivity2017In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 65, no 11, p. 5686-5696Article in journal (Refereed)
    Abstract [en]

    This paper revisit and extend the interesting case of bounds on the Q-factor for a given directivity for a small antenna of arbitrary shape. A higher directivity in a small antenna is closely connected with a narrow impedance bandwidth. The relation between bandwidth and a desired directivity is still not fully understood, not even for small antennas. Initial investigations in this direction have related the radius of a circumscribing sphere to the directivity, and bounds on the Q-factor have also been derived for a partial directivity in a given direction. In this paper, we derive lower bounds on the Q-factor for a total desired directivity for an arbitrarily shaped antenna in a given direction as a convex problem using semidefinite relaxation (SDR) techniques. We also show that the relaxed solution is also a solution of the original problem of determining the lower Q-factor bound for a total desired directivity. SDR can also be used to relax a class of other interesting nonconvex constraints in antenna optimization, such as tuning, losses, and front-to-back ratio. We compare two different new methods to determine the lowest Q-factor for arbitrary-shaped antennas for a given total directivity. We also compare our results with full electromagnetic simulations of a parasitic element antenna with high directivity.

  • 30.
    Li, Hui
    et al.
    Dalian Univ Technol, Sch Informat & Commun Engn, Dalian 116024, Peoples R China..
    Lau, Buon Kiong
    Lund Univ, Dept Elect & Informat Technol, SE-22100 Lund, Sweden..
    He, Sailing
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Design of Closely Packed Pattern Reconfigurable Antenna Array for MIMO Terminals2017In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 65, no 9, p. 4891-4896Article in journal (Refereed)
    Abstract [en]

    In this communication, a compact pattern reconfigurable dual-antenna array is designed at 2.65 GHz for multiple-input multiple-output (MIMO) terminal applications, such as laptops. Each antenna is composed of two layers, i.e., the monopole layer and the planar inverted-F antenna (PIFA) layer. By switching the p-i-n diodes on each layer, its radiation patterns can be varied between conical and boresight patterns. Two such identical antennas are placed side by side on a common ground plane for MIMO application, providing altogether four operating modes. The center-to-center separation between the antennas is 0.25 wavelength, to keep the overall array compact. To facilitate an isolation of above 17 dB over all the modes for this compact array, two decoupling techniques based on the decoupling slits and the shielding wall are effectively combined. The envelope correlation coefficients (ECCs) of the far-field patterns in the four modes are below 0.05 in free space, and below 0.1 for most cases in the indoor and outdoor scenarios. The only exception is the monopole-PIFA mode in the outdoor scenario, but the ECC is still below 0.3 for this case. The measured efficiencies of the antennas are between -1.7 (68%) and -0.7 dB (85%) for all the modes. Therefore, good diversity and MIMO performances are expected for the proposed design.

  • 31.
    Li, Hui
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Lau, Buon Kiong
    Ying, Zhinong
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Decoupling of Multiple Antennas in Terminals With Chassis Excitation Using Polarization Diversity, Angle Diversity and Current Control2012In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 60, no 12, p. 5947-5957Article in journal (Refereed)
    Abstract [en]

    Excitation of the chassis enables single-antenna terminals to achieve good bandwidth and radiation performance, due to the entire chassis being utilized as the main radiator. In contrast, the same chassis excitation phenomenon complicates the design of multiple antennas for MIMO applications, since the same characteristic mode of the chassis may be effectively excited by more than one antenna, leading to strong mutual coupling and severe MIMO performance degradation. In this paper, we introduce a design concept for MIMO antennas to mitigate the chassis-induced mutual coupling, which is especially relevant for frequency bands below 1 GHz. We illustrate the design concept on a dual-antenna terminal at 0.93 GHz, where a folded monopole at one chassis edge excites the chassis' fundamental electric dipolemode and a coupled loop at the other chassis edge excites its own fundamental magnetic dipole mode. Since the two radiationmodes are nearly orthogonal to each other, an isolation of over 30 dB is achieved. Moreover, we show that the antenna system can be conveniently modified for multiband operation, such as in the 900/1800/2600MHz bands. Furthermore, by controlling the phase of the feed current on the folded monopole, the two antennas can be co-located on the same chassis edge with an isolation of over 20 dB. The co-located dual-antenna prototype was fabricated and verified in the measurements.

  • 32. Li, Hui
    et al.
    Lin, Xianqi
    Lau, Buon Kiong
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Equivalent Circuit Based Calculation of Signal Correlation in Lossy MIMO Antennas2013In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 61, no 10, p. 5214-5222Article in journal (Refereed)
    Abstract [en]

    Correlation coefficient of received signals across a pair of antennas is a key performance indicator for multiple-input-multiple-output (MIMO) systems. For multipath environments with uniform 3-D angular power spectrum, the signal correlation between two antennas can be exactly calculated from their 3-D radiation patterns. When radiation patterns are unavailable, a simplified approach that only requires the antennas' scattering parameters can be used instead. However, the simpler method assumes lossless antennas and thus only works well for antennas with high radiation efficiencies. To take into account the antenna loss, the idea of equivalent circuit approximation is used in this paper to analytically separate the lossy components (resistance or conductance) from the lossy antenna arrays, using known scattering parameters and radiation efficiencies. The simplified method using S parameters can then be applied to obtain the correlation coefficient of the equivalent lossless antennas. The effectiveness of the method has been verified on antennas operating at a single mode, such as dipole or patch at its lowest resonant frequency. Good results were also obtained for the measured case of a dual-antenna mobile terminal, consisting of a monopole and a PIFA.

  • 33.
    Li, Hui
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Tan, Yi
    Lau, Buon Kiong
    Ying, Zhinong
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Characteristic Mode Based Tradeoff Analysis of Antenna-Chassis Interactions for Multiple Antenna Terminals2012In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 60, no 2, p. 490-502Article in journal (Refereed)
    Abstract [en]

    The design of multiple antennas in compact mobile terminals is a significant challenge, due to both practical and fundamental design tradeoffs. In this paper, fundamental antenna design tradeoffs of multiple antenna terminals are presented in the framework of characteristic mode analysis. In particular, interactions between the antenna elements and the characteristic modes and their impact on design tradeoffs are investigated in both theory and simulations. The results reveal that the characteristic modes play an important role in determining the optimal placement of antennas for low mutual coupling. Moreover, the ability of antenna elements to localize the excitation currents on the chassis can significantly influence the final performance. To demonstrate the effectiveness of the proposed approach, a dual-band, dual-antenna terminal is designed to provide an isolation of over 10 dB for the 900 MHz band without additional matching or decoupling structures. A tradeoff analysis of bandwidth, efficiency, effective diversity gain and capacity is performed over different antenna locations. Finally, three fabricated prototypes verify the simulation results for representative cases.

  • 34.
    Li, Hui
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Xiong, Jiang
    Yu, Yufeng
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    A Simple Compact Reconfigurable Slot Antenna With a Very Wide Tuning Range2010In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 58, no 11, p. 3725-3728Article in journal (Refereed)
    Abstract [en]

    A simple and compact slot antenna with a very wide tuning range is proposed. A 25 mm (roughly equal to lambda(H)/8, where lambda(H) corresponds to the highest frequency of the tuning range) open slot is etched at the edge of the ground. To achieve the tunability, only two lumped elements, namely, a PIN diode and a varactor diode are used in the structure. By switching the PIN diode placed at the open end of the slot, the slot antenna can resonate as a standard slot (when the switch is on) or a half slot (when the switch is off). Continuous tuning over a wide frequency range in those two modes can be achieved by adjusting the reverse bias (giving different capacitances) of the varactor diode loaded in the slot. Through optimal design, the tuning bands of the two modes are stitched together to form a very wide tuning range. The fabricated prototype has a tuning frequency range from 0.42 GHz to 1.48 GHz with S11 better than -10 dB, giving a frequency ratio (f(R) = f(u)/f(L)) of 3.52:1. The measured full spherical radiation patterns show consistent radiation characteristics of the proposed antenna within the whole tuning range.

  • 35.
    Liao, Qingbi
    et al.
    Ericsson AB, Filter & Antenna Syst, S-16483 Stockholm, Sweden..
    Fonseca, Nelson J. G.
    European Space Agcy, Antennas & Submillimeter Waves Sect, NL-2200 AG Noordwijk, Netherlands..
    Camacho, Miguel
    Univ Seville, Sch Phys, Dept Elect & Electromagnetism, Seville 41012, Spain..
    Palomares-Caballero, Angel
    Univ Granada UGR, Dept Signal Theory Telemat & Commun, Granada 18071, Spain..
    Mesa, Francisco
    Univ Seville, Dept Appl Phys 1, ETS Ingn Informat, Seville 41012, Spain..
    Quevedo-Teruel, Oscar
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Ray-Tracing Model for Generalized Geodesic-Lens Multiple-Beam Antennas2023In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 71, no 3, p. 2640-2651Article in journal (Refereed)
    Abstract [en]

    Geodesic lenses are a compelling alternative to traditional planar dielectric lens antennas, as they are low loss and can be manufactured with a simple mechanical design. However, a general approach for the design and analysis of more advanced geodesic-lens antennas has been elusive, limiting the available tools to rotationally symmetric surfaces. In this article, we present a fast and efficient implementation built on geometrical optics and scalar diffraction theory. A numerical calculation of the shortest ray path (geodesic) using an open-source library helps quantify the phase of the electric field in the lens aperture, while the amplitude is evaluated by applying ray-tube power conservation theory. The Kirchhoff-Fresnel diffraction formula is then employed to compute the far field of the lens antenna. This approach is validated by comparing the radiation patterns of a transversely compressed geodesic Luneburg lens (elliptical base instead of circular) with the ones computed using commercial full-wave simulators, demonstrating a substantial reduction in computational resources. The proposed method is then used in combination with an optimization procedure to study possible compact alternatives of the geodesic Luneburg lens with size reduction in both the transverse and vertical directions.

  • 36.
    Liao, Qingbi
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Fonseca, Nelson
    Antenna and Sub-Millimeter Waves Section, European Space Agency, Noordwijk, 2200 AG, Netherlands.
    Quevedo-Teruel, Oscar
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Compact Multibeam Fully Metallic Geodesic Luneburg Lens Antenna Based on Non-Euclidean Transformation Optics2018In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 66, no 12, p. 7383-7388Article in journal (Refereed)
    Abstract [en]

    Non-Euclidean transformations have been recently proposed to produce a link between 3-D homogeneous surfaces and 2-D dielectric lenses. Therefore, the propagation in a geometrical surface has the same response of an equivalent refractive index distribution. By using this concept, we propose here a fully metallic Luneburg lens where the propagation is only in the air. Two metallic plates, following a curved shape, are employed to support the propagation mimicking the designed curvature. To reduce the height of the required curvature, the surface has been mirrored twice with respect to two z constant planes. The lens is fed by 11 waveguide ports spaced with an angle of 12.5° providing 1-D beam scanning over an angular range of ±62.5°. A prototype is manufactured and measured with a good agreement with the simulated results between 25 and 36 GHz to demonstrate the concept.

  • 37.
    Liao, Qingbi
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Rajo-Iglesias, Eva
    Univ Carlos III Madrid, Dept Commun & Signal Theory, Leganes 28911, Spain..
    Quevedo-Teruel, Oscar
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Ka-Band Fully Metallic TE40 Slot Array Antenna With Glide-Symmetric Gap Waveguide Technology2019In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 67, no 10, p. 6410-6418Article in journal (Refereed)
    Abstract [en]

    Gap waveguide has recently been proposed as a low-loss and low-cost technology for millimeter-wave components. The main advantage of the gap waveguide technology is that the microwave components can be manufactured in two metallic pieces that are assembled together without electrical contact. The leakage through a thin air gap between the two pieces is prevented by a 2-D periodic structure offering an electromagnetic bandgap (EBG). This EBG is conventionally implemented with metallic pins. Here, we propose the usage of a holey glide-symmetric EBG structure to design a $4\times 4$ slot array antenna that is fed with a TE40 mode. The TE40 excitation is designed based on a TE10-TE20 mode converter whose performance is initially evaluated by radiation pattern measurements. The final antenna, the $4\times 4$ slot array antenna, was manufactured in aluminum by computer numerical control (CNC) milling. The antenna has a rotationally symmetric radiation pattern that could find application as a reference antenna as well as for 5G point-to-point communications.

  • 38. Lin, Zhili
    et al.
    Thylén, Lars
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    On the Accuracy and Stability of Several Widely Used FDTD Approaches for Modeling Lorentz Dielectrics2009In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 57, no 10, p. 3378-3381Article in journal (Refereed)
    Abstract [en]

    A rigorous and comparative study on the approximation accuracy and stability limits of several widely used finite-difference time-domain (FDTD) approaches, namely the auxiliary differential equation (ADE) approach, the bilinear transform (BT) approach, the Z-transform approach (ZT) and the piecewise linear recursive convolution (PLRC) approach, for modeling dispersive Lorentz dielectrics is presented following the given updating equations between the electric flux density and the electric field intensity. We find the ZT approach with modified material parameters is much more accurate than the original ZT approach and the other three approaches for modeling Lorentz dielectrics. The stability limits of the ADE, ZT and PLRC approaches in simulating Lorentz dielectrics are also shown to be a bit more stringent than that of BT approach which preserves the Courant stability limit as previously reported.

  • 39. Lindmark, B.
    et al.
    Lundgren, S.
    Sanford, JR.
    Beckman, Claes
    Chalmers University of Technology, Sweden.
    Dual-polarized array for signal-processing applications in wireless communications1998In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 46, no 6, p. 758-763Article in journal (Refereed)
    Abstract [en]

    A novel dual-polarized antenna array designed for a spatial division multiple access (SDMA) system working in the 1850-1990-MHz band is designed and built. The antenna is designed to have similar element patterns, and measurements of S-parameters and radiation patterns are presented. The array signal processing performance of the array using all elements and with no compensation for mutual coupling or differences in element patterns is studied through direction-of-arrival (DOA) estimation using total least squares estimation of signal parameters via rotational invariance techniques (TLS-ESPRIT). The results show that the accuracy of the DOA estimates is quite acceptable for wireless communication applications.

  • 40.
    Lindmark, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Comparison of mutual coupling compensation to dummy columns in adaptive antenna systems2005In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 53, no 4, p. 1332-1336Article in journal (Refereed)
    Abstract [en]

    Compensation for mutual coupling in antenna arrays by matrix multiplication is compared to the use of dummy elements. A least squares estimation of the coupling matrix is made, including co- and cross-polar coupling. We show that compensation for measurements off the phase center is important as well as a proper assumption of the ideal element pattern. We study the performance of a dual polarized patch array with respect to far-field phase error, signal-to-interference reduction, and cross-polarization level. In all aspects, the performance of the compensation method exceeds or equals the use of dummy elements.

  • 41.
    Ludvig-Osipov, Andrei
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering. Chalmers Univ Technol, Dept Elect Engn, S-41296 Gothenburg, Sweden..
    Hannula, Jari-Matti
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Naccachian, Patricia
    Amer Univ Beirut, Dept Elect & Comp Engn, Beirut 10999, Lebanon..
    Jonsson, B. Lars G.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Physical Limitations of Phased Array Antennas2021In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 69, no 9, p. 5512-5523Article in journal (Refereed)
    Abstract [en]

    In this article, the bounds on the Q-factor, a quantity inversely proportional to bandwidth, are derived and investigated for narrowband phased array antennas. Arrays in free space and above a ground plane are considered. The Q-factor bound is determined by solving a minimization problem over the electric current density. The support of these current densities is on an element-enclosing region, and the bound holds for lossless antenna elements enclosed in this region. The Q-factor minimization problem is formulated as a quadratically constrained quadratic optimization problem that is solved either by a semi-definite relaxation or an eigenvalue-based method. We illustrate numerically how these bounds can be used to determine tradeoff relations between the Q-factor and other design specifications: element form factor, size, efficiency, scanning capabilities, and polarization purity.

  • 42.
    Ludvig-Osipov, Andrei
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Jonsson, B. Lars G.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Stored Energies and Q-Factor of Two-Dimensionally Periodic Antenna Arrays2020In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 68, no 8, p. 5989-6002Article in journal (Refereed)
    Abstract [en]

    The Q-factor for lossless 3-D structures with 2-D periodicity is here derived in terms of the electric current density. The derivation in itself is shape-independent and based on the periodic free-space Green's function. The expression for Q-factor takes into account the exact shape of a periodic element and permits beam steering. Both the stored energies and the radiated power, required to evaluate Q-factor, are coordinate-independent and expressed in a similar manner to the periodic electric field integral equation and can thus be rapidly calculated. Numerical investigations, performed for several antenna arrays, indicate fine agreement, accurate enough to he predictive, between the proposed Q-factor and the tuned fractional bandwidth, when the arrays are not too wideband (i.e., when Q >= 5) . For completeness, the input-impedance Q-factor, proposed by Yaghjian and Best in 2005, is included and agrees well numerically with the derived Q-factor expression. The main advantage of the proposed representation is its explicit connection to the current density, which allows the Q-factor to give bandwidth estimates based on the shape and current of the array element.

  • 43.
    Ludvig-Osipov, Andrei
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Lundgren, Johan
    Department of Electrical and Information Technology, Lund University, Lund SE-22100, Sweden.
    Ehrenborg, Casimir
    Department of Physics and Electrical Engineering, Linnæus University, Växjö SE-35195, Sweden.
    Ivanenko, Yevhen
    Department of Electrical and Information Technology, Lund University, Lund SE-22100, Sweden.
    Ericsson, Andreas
    Lund University, Lund SE-221 00, Sweden;TICRA, Copenhagen DK-1119, Denmark.
    Gustafsson, Mats
    Department of Electrical and Information Technology, Lund University, Lund SE-22100, Sweden.
    Jonsson, B. Lars G.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Sjöberg, Daniel
    Department of Electrical and Information Technology, Lund University, Lund SE-22100, Sweden.
    Fundamental bounds on transmission through periodically perforated metal screens with experimental validation2020In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 68, no 2, p. 773-782, article id 8852810Article in journal (Refereed)
    Abstract [en]

    This paper presents a study of transmission through arrays of periodic sub-wavelength apertures. Fundamental limitations for this phenomenon are formulated as a sum rule, relating the transmission coefficient over a bandwidth to the static polarizability. The sum rule is rigorously derived for arbitrary periodic apertures in thin screens. By this sum rule we establish a physical bound on the transmission bandwidth which is verified numerically for a number of aperture array designs. We utilize the sum rule to design and optimize sub-wavelength frequency selective surfaces with a bandwidth close to the physically attainable. Finally, we verify the sum rule and simulations by measurements of an array of horseshoe-shaped slots milled in aluminum foil.

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  • 44.
    Malmström, Johan
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering. Saab Surveillance, SE-17588 Stockholm, Sweden..
    Holter, Henrik
    Saab Surveillance, Elect Warfare Div, SE-17588 Stockholm, Sweden..
    Jonsson, B. Lars G.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    On the Accuracy of Equivalent Antenna Representations - A Case Study2018In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 66, no 7, p. 3251-3260Article in journal (Refereed)
    Abstract [en]

    The accuracy of two equivalent antenna representations, near-field sources and far-field sources (FFSs), is evaluated for an antenna installed on a simplified platform. We show that the accuracy of the installed far-field and surface current for the investigated weakly scattering platform depends strongly on the configurations associated with the equivalent antenna representation. The root-mean-square error for the installed far-field error varies between 4.4%-8.4% for the considered configurations of near-field equivalent representations installed on the investigated platform. When using FFSs, the design parameters have an even larger influence of the achieved accuracy. There is also a varying accuracy depending on the type of numerical method used. Based on the results, some recommendations on the choice of subdomain for the equivalent antenna representation are given associated with the platform. In industrial antenna applications, the accuracy in determining, e.g., installed far-fields and antenna isolation on large platforms is critical. Equivalent representations can reduce the fine-detail complexity of antennas and thus give an efficient numerical description to be used in large-scale simulations. The results, in this paper, highlight to antenna designers and system engineers the accuracy challenges associated with the use of equivalent antenna representations.

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  • 45.
    Motevasselian, Alireza
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Ellgardt, Anders
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Jonsson, B. Lars G.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    A Circularly Polarized Cylindrical Dielectric Resonator Antenna Using a Helical Exciter2013In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 61, no 3, p. 1439-1443Article in journal (Refereed)
    Abstract [en]

    A novel circularly polarized cylindrical dielectric resonator antenna excited by an external tape helix is presented. The helix is fed by a coaxial line through a small hole on a finite size ground plane. The configuration offers a compact and easy to fabricate feeding network providing a 3 dB axial-ratio bandwidth of 6.4%. A prototype of the proposed configuration is fabricated and measured. Measured and simulated return loss, axial-ratio, radiation pattern, and realized gain are presented and discussed together with design guidelines.

  • 46.
    Orgeira, Omar
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Leon, German
    Univ Oviedo, Dept Elect Engn, Gijon 33204, Spain..
    Fonseca, Nelson J. G.
    European Space Agcy, Antenna & Sub Millimetre Waves Sect, NL-2200 AG Noordwijk, Netherlands..
    Mongelos, Pedro
    Arcelor Mittal Global Res & Dev, Addit Mfg Dept, Aviles 33490, Spain..
    Quevedo-Teruel, Oscar
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electromagnetic Engineering.
    Near-Field Focusing Multibeam Geodesic Lens Antenna for Stable Aggregate Gain in Far-Field2022In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 70, no 5, p. 3320-3328Article in journal (Refereed)
    Abstract [en]

    The millimeter-wave band is a very attractive frequency band for the new generations of mobile cellular networks, i.e. 5G and 6G, due to its potential to support extremely high data rate transmissions. Innovative antenna solutions are needed to relieve the higher free space attenuation at these frequencies. Here, we propose a multibeam antenna based on a geodesic lens with stable aggregate gain characteristics in the far-field. An analytical model based on the physical path of the rays inside the lens is applied to achieve the field distribution in the aperture of the lens. This method is used to find the profile of a near-field focusing lens with a widened beam in the far-field. As a proof of concept, a seven-beam antenna has been designed. Due to the rotational symmetry of the geodesic lens, the antenna beams present similar characteristics over an extended sectorial coverage. The lens antenna has been manufactured, and its near-field focusing features were validated. The prototype has been assessed also in the far-field with a good agreement between model, simulations, and measurements. The main novelty of this prototype is to achieve a multiple beam coverage within +/- 67 degrees in the H-plane and +/- 20 degrees in the E-plane, with a gain roll-off smaller than 2 dB at 30 GHz and smaller than 3 dB at 35 GHz. These results validate the stable aggregate gain characteristics in the far-field of the proposed solution.

  • 47.
    Osseiran, Afif
    et al.
    Ericsson Research, Ericsson AB, Stockholm, Sweden.
    Logothetis, Andrew
    Ericsson Research, Ericsson AB, Stockholm, Sweden.
    Smart antennas in a WCDMA Radio Network System Revisited: Modeling and Evaluations2006In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 54, no 11, p. 3302-3316Article in journal (Refereed)
    Abstract [en]

    A comprehensive study is given of smart antennas for wide-band code-division multiple access (WCDMA). It analyzes, evaluates, and presents methods and ideas for the deployment of smart antennas in WCDMA third-generation wireless systems and for future generations. Three major implementations are evaluated and analyzed in a dynamic system simulator: higher order sectorization (HOS), fixed beams (FBs) with secondary common pilot channel (S-CPICH), and FBs with primary common pilot channel (P-CPICH) as a phase reference. The system modeling integrates antenna and wave propagation modeling to evaluate and design smart antennas in wireless communications. Furthermore, this paper analyzes the impact of angular spread of various antenna configurations, the interaction and impact of radio resource management as power tuning of the common channel, scrambling code (SCO) allocation technique, and soft and softer handover algorithm. Moreover, an SCO allocation strategy and an adaptive load-dependent power-tuning algorithm of the P-CPICH are proposed. Furthermore, a signal-to-(interference plus noise) ratio derivation is given. Extensive simulation studies are carried out to evaluate the capacity gains of HOS and FB. The 12-sector sites yield the best system downlink capacity gain compared to three-sector sites equipped with a single antenna, slightly more than three-sector sites equipped with four FBs each. The six-sector sites equipped with two FBs each reduce the gap between HOS and FB systems to 10%.

  • 48.
    Persson, Patrik
    et al.
    KTH, Superseded Departments (pre-2005), Electromagnetic Theory.
    Josefsson, L
    Calculating the mutual coupling between apertures on a convex circular cylinder using a hybrid UTD-MoM method2001In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 49, no 4, p. 672-677Article in journal (Refereed)
    Abstract [en]

    In this paper, the problem of calculating the mutual coupling between apertures on a perfectly conducting circular cylinder is considered. The mutual coupling is calculated by a combination of uniform theory of diffraction (UTD) and the method of moments (MoM). This hybrid method makes it possible to include higher order aperture modes in order to improve the accuracy. It is found that the UTD-MoM solution gives accurate results, even for small cylinders. The results are verified against results found in the literature, as well as against measurements performed at Ericsson Microwave System in Molndal, Sweden. For this purpose, a cylindrical test antenna with 54 apertures was built. Using a single-mode approximation, good agreement down to about -60 dB, comparisons to measured data has been obtained. If additional modes are added the results improve significantly both in amplitude and phase, Zn several cases, the agreement is good down to coupling levels about -80 dB. This requires that about six modes are included. However, the most important mode, besides the fundamental TE10 mode is the TM11 mode.

  • 49.
    Persson, Patrik
    et al.
    KTH, Superseded Departments (pre-2005), Electromagnetic Theory.
    Josefsson, L
    Lanne, M
    Investigation of the mutual coupling between apertures on doubly curved convex surfaces: Theory and measurements2003In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 51, no 4, p. 682-692Article in journal (Refereed)
    Abstract [en]

    A hybrid method of high-frequency approximation (UTD) and method of moments is used to calculate. the mutual coupling between circular apertures on a doubly curved surface. This requires that the geodesics on doubly curved surfaces be found. To represent the aperture fields, a single waveguide mode approximation is used. In order to verify the theoretical results, a general paraboloid of revolution with circular waveguide-fed apertures was built at Ericsson Microwave Systems AB, Molndal, Sweden. This has given a possibility to verify the theoretical model for a general doubly curved surface against measurements. To the authors' knowledge, no such verification is available in the literature. It was found that measured and theoretical results in terms of mutual coupling agree very well for copolar coupling. As expected, the mutual coupling results are very dependent on the polarization. In fact, the definition of polarization directions and the heed for polarization control are important issues for doubly curved conformal array antennas.

  • 50. Rajo-Iglesias, Eva
    et al.
    Gallego-Gallego, Iria
    Inclan-Sanchez, Luis
    Quevedo-Teruel, Oscar
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Textile Soft Surface for Back Radiation Reduction in Bent Wearable Antennas2014In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 62, no 7, p. 3873-3878Article in journal (Refereed)
    Abstract [en]

    A textile soft surface is proposed to reduce back radiation of a textile patch antenna, and the performance is analyzed when the antenna is placed on a bent surface. This surface is assumed to be curved around cylinders with varying radii to emulate the real operation of the textile antenna when it is worn on the body, e. g., back, shoulders or arms. Two scenarios are considered for the evaluation of the performance of the antenna with the soft surface: a bent finite ground plane over an air cylinder and a more accurate model in which the electromagnetic properties of the body are included. In both situations the back radiation is reduced when compared to the same antenna without the soft surface. These results have been validated with experimental data which support this conclusion. This is the first textile implementation of a soft surface and the first demonstration that a soft surface can reduce the back radiation of a patch antenna in a conformal configuration.

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