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  • 1. Beckman, C.
    et al.
    Eklund, L.
    Karlsson, B.
    Lindmark, Björn
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Ribbenfjärd, David
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Wirdemark, P.
    Verifying 3G license requirements when every dB is worth a billion2006In: Eur Space Agency Spec Publ ESA SP, 2006Conference paper (Refereed)
    Abstract [en]

    In the year 2000, the Swedish Telecom regulator: "Post& Telestyrelsen", PTS, granted in a "beauty contest" four licenses for operations of 3G systems. To verify the coverage and the license requirements, PTS, has developed a test procedure where the field strength of the primary Common Pilot Channel, CPICH, is measured in a drive test. Designing such a test constitutes a number of challenges mainly due to the fact that in 3G the accuracy in the measurement needs to be extremely high since even a small systematic error of ∼1dB could in Sweden have the consequence that each operator would have to build an extra +1000 sites at a staggering cost of ∼1bilion SEK! The present paper gives an overview of the considerations behind the design of the test method used for verification of the 3G licence requirements in Sweden.

  • 2.
    Beckman, Claes
    et al.
    University of Gävle.
    Eklund, Lars
    Karlsson, Bo
    Lindmark, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Ribbenfjärd, David
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Wirdemark, Per
    Verifying 3G licence requirements when every dB is worth a billion2006In: First European Conference on Antennas & Propagation: EuCAP 2006 / [ed] H. Lacoste & L. Ouwehand, 2006, p. 1-4Conference paper (Refereed)
    Abstract [en]

    In the year 2000, the Swedish Telecom regulator: “Post&Telestyrelsen”, PTS, granted in a “beauty contest” four licenses for operations of 3G systems. To verify the coverage and the license requirements, PTS, has developed a test procedure where the field strength of the primary Common Pilot Channel, CPICH, is measured in a drive test. Designing such a test constitutes a number of challenges mainly due to the fact that in 3G the accuracy in the measurement needs to be extremely high since even a small systematic error of ~1dB could in Sweden have the consequence that each operator would have to build an extra +1000 sites at a staggering cost of ~1billion SEK!

    The present paper gives an overview of the considerations behind the design of the test method used for verification of the 3G licence requirements in Sweden.

  • 3.
    Beckman, Claes
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Center for Wireless Systems, Wireless@kth.
    Lindmark, Björn
    The evolution of base station antennas for mobile communications2007In: International Conference on Electromagnetics in Advanced Applications: ICEAA 07, IEEE conference proceedings, 2007, p. 85-92Conference paper (Refereed)
    Abstract [en]

    This paper gives a general overview of the design of base station antennas for mobile communications. It explains underlying theoretical and practical implementation aspects in mobile communication networks of today and the future. In the first part the fundamental parameters of a base station antenna are discussed in the context of radio network design. In particular we discuss parameters such as gain, radiation patterns, frequency bands and power handling and put them in the context of cell planning, propagation and capacity. In the final parts of the paper we give an overview of the underlying theory of diversity and MIMO systems.

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  • 4. Freni, A.
    et al.
    Lindmark, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Maci, S.
    Mariottini, F.
    The european school of antennas: A new model of distributed PhD school2005Conference paper (Refereed)
  • 5. Freni, A.
    et al.
    Lindmark, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Maci, S.
    Mariottini, F.
    The European school of antennas within the ACE network2005In: 35th European Microwave Conference 2005: Conference Proceedings, 2005, p. 793-796Conference paper (Refereed)
    Abstract [en]

    The Antenna Center of Excellence (ACE) Is a Network of Excellence funded by the EC 6th Framework Program. This paper describes the activities on Training and Education within the network and In particular the organization of a European School of Antennas with short courses on different antenna related topics taught be recognized experts In the respective fields.

  • 6. Garcia-Garcia, L.
    et al.
    Jaldén, Niklas
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Lindmark, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Zetterberg, Per
    KTH, School of Electrical Engineering (EES), Signal Processing.
    De Haro, L.
    Measurements of MIMO capacity at 1800 MHZ with in- and outdoor transmitter locations2006In: European Space Agency, 2006, no Special Publication) ESA SP, 626 SP, 6 p.Conference paper (Refereed)
    Abstract [en]

    A measurement campaign was carried out to analyse several possible transmitter locations for a 4x4 MIMO system. The receiver modules were moved along indoor routes, and both indoor and outdoor locations were considered for the transmitters. The spatial correlation, path loss and capacity were analysed. Also several options regarding signal combination at system level were studied, assuming two base stations with 2 antennas each. As a result, it is shown that the 2x4 configuration with base station selection and waterfilling scheme provides almost as good performance as a 4x4 full waterfilling scheme when the 2 base stations are spatially separated. This solution may be very interesting to reduce system complexity without significant loss of performance.

  • 7. Garcia-Garcia, L.
    et al.
    Lindmark, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Jaldén, Niklas
    KTH, School of Electrical Engineering (EES), Signal Processing.
    De Haro, L.
    Multi-user MIMO capacity from measurements in indoor environment with in- and outdoor base stations2007In: 2nd European Conference on Antennas and Propagation (EuCAP 2007), 2007, no 11961Conference paper (Refereed)
    Abstract [en]

    MIMO systems have been widely studied in recent years, and several characteristics of the radio channel have been studied and analysed. One aspect of great interest is the analysis and optimization of parameters regarding the base station when multiple antennas are used at the receiver and the transmitter. Moreover, when not only the link-level but also the system- level is to be studied, the system performance when multiple users are considered is of importance. By using the channel measurements obtained with different base station locations and multiple routes in an indoor scenario, we present in this paper the results for a multi-user MIMO system when different possibilities in location and signal combination or cooperation for base stations are compared. Results are shown in terms of sum-capacity, which is evaluated for different transmit methods (with and without CSI) and base station locations, and it is compared with the capacity in a single user system (with and without interference).

  • 8.
    Garcia-Garcia, Laura
    et al.
    Dept. of Signals, Systems and Radiocommunications Universidad Politécnica de Madrid (UPM), 28040 Madrid (Spain) .
    Jaldén, Niklas
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Lindmark, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Zetterberg, Per
    KTH, School of Electrical Engineering (EES), Signal Processing.
    de Haro, Leandro
    Dept. of Signals, Systems and Radiocommunications Universidad Politécnica de Madrid (UPM), 28040 Madrid (Spain) .
    Measurements of MIMO indoor channels at 1800 MHz with multiple indoor and outdoor base stations2007In: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499Article in journal (Refereed)
    Abstract [en]

    This paper proposes several configurations for multiple base stations in indoor MIMO systems and compares their performance. The results are based on channel measurements realized with a MIMO testbed. The receiver was moved along several routes and floors on an office building. Both outdoor and indoor locations are considered for the transmitters or base stations, which allow the analysis of not only indoor but also outdoor-to-indoor environment. The use of 2 base stations with different system level combinations of the two is analyzed. We show that the 2 x 4 configuration with base station selection provides almost as good performance as a 4 x 4 full water-filling scheme when the 2 base stations are placed at different locations. Also the spatial correlation properties for the different configurations are analyzed and the importance of considering path loss when evaluating capacity is highlighted.

  • 9.
    Garcia-Garcia, Laura
    et al.
    2Dep. SSR, Universidad Politecnica de Madrid, 28040 Madrid Spain.
    Lindmark, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Jaldén, Niklas
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Orlenius, Charlie
    MIMO capacity of antenna arrays evaluated using radio channel measurements, reverberation chamber and radiation patterns2007In: IET Microwaves, Antennas and Propagation, ISSN 1751-8725, Vol. 1, no 6, p. 1160-1169Article in journal (Refereed)
    Abstract [en]

    We compare different methods of evaluating arrays for multiple-input multiple-output (MIMO) systems through calculation of the MIMO capacity of a compact antenna array for mobile or WLAN applications at 1766 MHz and comparing it to a reference array of four mono-poles. Three different methods were used: evaluation using radiation patterns and a channel model, measurements in a reverberation chamber and simultaneous measurement of radio channel data using the two arrays. We conclude that all methods give very similar relative results and that the main difference in the two arrays is the 1.3 dB lower radiation efficiency of the compact array. The channel measurements also show that the arrays provide between 80% and 90% of the capacity of a 4 x 4 MIMO system.

  • 10.
    Garcia-Garcia, Laura
    et al.
    Dept. of Signals, Systems and Radiocommunications Universidad Politécnica de Madrid (UPM), 28040 Madrid (Spain) .
    Lindmark, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Orlenius, Charlie
    Dep. Signals and Systems, Chalmers Univ. of Tech., 412 96 Gothenburg, Sweden.
    Design and evaluation of a compact antenna array for MIMO applications2006In: Antennas and Propagation Society International Symposium 2006, IEEE, IEEE , 2006, p. 313-316Conference paper (Refereed)
    Abstract [en]

    A compact MIMO array suited for a PDA application at 1766 and 2450 MHz is presented. We chose a configuration which both maximizes the distance between the elements, and provides full polarization diversity. The performance of the array at 1766 MHz has been presented in terms of S-parameters, efficiency, calculated covariance and capacity. We conclude that the major difference between the proposed array and an ideal monopole reference array lies in the slightly lower radiation efficiency.

  • 11. Godi, G.
    et al.
    Pascaud, R.
    Gillard, R.
    Loison, R.
    Wiart, J.
    Wong, M. F.
    Lindmark, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Garcia-Garcia, L.
    Applications of the DG-FDTD method2007In: 2nd European Conference on Antennas and Propagation, EuCAP 2007, 2007, no 11961Conference paper (Refereed)
    Abstract [en]

    In this paper, we propose to use the dual-grid finite-difference time-domain (DG-FDTD) approach to analyze the characteristics of several antenna configurations. This method reduces the overall computational time and besides, it prevents from instabilities. It has been applied to the analysis of far-field and impedance characteristics of an integrated lens antenna and of a MIMO array. A dosimetry problem for phone / head interaction is also presented in the paper.

  • 12.
    González, Alejandro N.
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Lindmark, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing.
    The effect of antenna orientation and polarization on MIMO capacity2005Conference paper (Refereed)
    Abstract [en]

    The capacity of a Multiple-Input Multiple-Output (MIMO) system depends on the channel matrix as well as the Signal-to-Noise ratio. In this paper the effect of the antenna orientation is analyzed for both single polarized and dual polarized antennas using a planar channel model. The results show that although linear polarized TX and RX antennas provide higher capacity when they are polarization matched, dual polarized antennas provide better performance when an arbitrary orientation is considered.

  • 13.
    Lindmark, Björn
    KTH, Superseded Departments (pre-2005), Signals, Sensors and Systems.
    Capacity of a 2x2 MIMO antenna system with mutual coupling losses2004In: IEEE ANTENNAS AND PROPAGATION SOCIETY SYMPOSIUM, VOLS 1-4 2004, DIGEST, IEEE , 2004, p. 1720-1723Conference paper (Refereed)
    Abstract [en]

    The capacity of Multiple-Input Multiple-Output (MIMO) systems is strongly dependent on the channel matrix which in turn can be expressed in integrals over the antenna far-0 eld patterns. In this paper the effect of mutual coupling on the capacity of a 2 x 2 MIMO system is studied. The results show that even though the correlation is reduced the losses caused by mutual coupling decrease the capacity as we reduce the antenna spacing.

  • 14.
    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.

  • 15.
    Lindmark, Björn
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Garcia-Garcia, Laura
    2Dep. SSR, Universidad Politecnica de Madrid, 28040 Madrid Spain.
    Compact antenna array for MIMO applications at 1800 and 2450 MHz2006In: Microwave and optical technology letters (Print), ISSN 0895-2477, E-ISSN 1098-2760, Vol. 48, no 10, p. 2034-2037Article in journal (Refereed)
    Abstract [en]

    A novel dual band array for MIMO applications at 1766 and 2450 MHz is presented. The array consists of four patch elements placed on a 125 X 75 mm(2) device. The effect a of different orientation and element placement is discussed and the final array is analyzed with respect to antenna covariance calculated from measured radiation patterns. We conclude that the array differs from an ideal monopole array by a 1.3 dB lower radiation efficiency.

  • 16.
    Lindmark, Björn
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Garcia-Garcia, Laura
    2Dep. SSR, Universidad Politecnica de Madrid, 28040 Madrid Spain.
    Jaldén, Niklas
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Orlenius, Charlie
    Evaluation of MIMO arrays using antenna patterns, reverberation chamber, and channel measurements2006In: Antennas and Propagation, 2006. EuCAP 2006. First European Conference on, European Space Agency, 2006, p. 1-6Conference paper (Refereed)
    Abstract [en]

    We have compared different methods of evaluating arrays for MIMO systems. We calculated the MIMO capacity of a compact antenna array for mobile or WLAN applications at 1766 MHz and compared it to a large reference array of 4 monopoles. Three different methods were used: evaluation using radiation patterns and a channel model, measurements in a reverberation chamber, and simultaneous measurement of radio channel data using the two arrays. We conclude that the main difference in the to arrays is the 1.3 dB lower efficiency of the compact array.

  • 17.
    Lindmark, Björn
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Zetterberg, Per
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Garcia-Garcia, L.
    Macro-cellular MIMO with dual polarized base station antennas and different spacing2007In: IET Seminar Digest, 2007, Vol. 2007, no 11961), .Conference paper (Refereed)
    Abstract [en]

    We present a theoretical analysis of the joint effect of azimuth spread, base station antenna spacing, and environment cross-polar discrimination on the capacity of a 4 x 4 MIMO system using dual polarized antennas. The results indicate that a spatial separation of 3 wavelengths is sufficient for near-optimal MIMO operation. We also present analysis of channel measurements from urban Stockholm which shows that two dual polarized base station antennas with a spacing of only 1.12 wavelengths at 1747 MHz increases the capacity by 50% compared to a single dual polarized antenna.

  • 18. Maci, S.
    et al.
    Lindmark, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Freni, A.
    The European School of Antennas: The new model of distributed PhD school of the Antenna Center of Excellence2005In: IEEE Antennas & Propagation Magazine, ISSN 1045-9243, E-ISSN 1558-4143, Vol. 47, no 4, p. 120-125Article in journal (Refereed)
    Abstract [en]

    The European School of Antennas is a new model of a geographically distributed PhD school, which aims to improve the advanced antenna training and research in Europe. The school is organized in the framework of the Antenna Center of Excellence (ACE), a "Network of Excellence" financed by the sixth framework program of the European Union. The school is constituted as a highly qualified integrated set of advanced courses at the PhD level, distributed in the most accredited European research centers on antennas. The general objectives of the school are: i) strengthening the European excellence on antennas; ii) completing the individual PhD curricula of students in electrical and information engineering by offering interaction with the best trainers in Europe; iii) increasing the link between European universities and industries in antenna research and development; and iv) facilitating the interchange of ideas among early-stage researchers and teachers, thus increasing the future mobility and synergy. The school is furnished with centralized Web support, and this is coordinated so that the courses have the same format and apply common basic rules for exams and credits.

  • 19. Modaresi, M.
    et al.
    Shafai, L.
    Lindmark, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Efficient optimization of a Yagi-Uda antenna using genetic algorithm2017In: ANTEM 2005 - 11th International Symposium on Antenna Technology and Applied Electromagnetics, Conference Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2017, article id 7852127Conference paper (Refereed)
    Abstract [en]

    In this paper, Yagi-Uda antenna is studied and analyzed considering a single mode cosine current distribution on all elements. A classical approach is taken for the analysis, by viewing Yagi antenna as a center-driven dipole array in which all but the actual exciter element are short-circuited at the terminals. Currents are induced in the elements via the mutual impedances, and radiation occurs as from a set of discrete sources. The mutual impedance matrix of the array is calculated using the induced EMF method and integral equations for the electric field. This analysis has led to a fast and efficient code to calculate Yagi parameters. The validity of the results has been checked with a MoM solution using NEC2 and good agreement has been observed. Then, the code is used together with a genetic algorithm in order to optimize Yagi-Uda antenna for gain maximization. A 31-element high gain Yagi with 19.2dB gain and the gain bandwidth of 8 percent is derived. Also the Pareto fronts are plotted for Yagi antennas with different number of elements which shows the trade off between the directivity and front to back lobe(F/B) ratio.

  • 20. Moldovan, Eugen
    et al.
    Lindmark, Björn
    KTH, Superseded Departments (pre-2005), Signals, Sensors and Systems.
    Slättman, Peter
    Optimization of a Stacked Patch Antenna for High Directivity2004In: 13èmes Journées Internationales de Nice sur les Antennes (JINA), 2004, p. 317-372Conference paper (Refereed)
    Abstract [en]

    We present a probe-fed stacked microstrip patch antenna optimized for high directivity. The optimizationprocedure uses a Method-of-Moment simulation code which shows very good agreement with measurements.Using 4 patches we achieve a directivity of 13.1 dB for a finite ground plane and 14.9 dB for an infiniteground plane which is higher than previously reported for a patch antenna. A discussion of the antennaoperation using equivalent dipole moments shows that the behavior is similar to a Yagi-Uda antenna.

  • 21.
    Mowlér, Marc
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Signal Processing.
    Khalid, Bilal
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Signal Processing.
    Lindmark, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Reconfigurable Monopole Array with MEMS Switches for MIMO Systems2008In: 2008 IEEE Antennas And Propagation Society International Symposium: Vols 1-9, 2008, p. 1028-1031Conference paper (Refereed)
    Abstract [en]

    We have presented a reconfigurable monopole antenna and have analyzed it in terms of reflection losses and radiation patterns for different configurations. The correlations between different configurations were found to be reasonably low, so we may be able to successfully use our antenna array for capacity and throughput enhancement purposes. We are currently conducting MIMO capacity measurements with the presented array to analyze the amount of increase in throughput, but the fact that we are able to change the radiation pattern indicates the possibility of improving the overall MIMO channel.

  • 22.
    Mowlér, Marc
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Khalid, Bilal
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Lindmark, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Ottersten, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Capacity and Gain Analysis of a Reconfigurable MEMS Antenna2008In: Nordic Conference on Radio Science and Communications (RVK), 2008Conference paper (Other academic)
    Abstract [en]

    This paper presents the investigation results on therecon¯gurable properties of an antenna array compris-ing of four feed elements and four parasitic elementsplaced on a ¯nite ground plane. This antenna is in-tended to improve the diversity gain for a Multiple In-put Multiple Output (MIMO) communication system.We intend to use a recon¯gurable antenna to com-bat the problem of signal deterioration in a handhelddevice so that it can get optimum signal strength inany orientation. With our presented antenna, we canachieve up to sixteen di®erent con¯gurations depend-ing on the requirement. The di®erent con¯gurationsare controlled with the help of RF switches which areimplemented using micro-electromechanical systems(MEMS). The recon¯gurable antenna was fabricatedand tested for its impedance and radiation character-istics and the results were found to be in reasonable agreement with the simulations. Channel measure-ments were made with the help of a MIMO test setup.

  • 23.
    Mowlér, Marc
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Khalid, Bilal
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Lindmark, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Ottersten, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Switched MEMS Antenna for Handheld Devices2008In: ICT-MobileSummit 2008, 2008Conference paper (Refereed)
    Abstract [en]

    This paper presents the investigation results on the reconfigurableproperties of a monopole antenna array. The antenna array comprises of four feedelements and four parasitic elements on a finite ground plane. This antenna isintended to improve the diversity gain for a Multiple Input Multiple Output (MIMO)communication system. We intend to combat the problem of signal deterioration inhandheld devices by the use of reconfigurable antenna. A common communicationproblem seen in the handheld devices is the change in strength of radio signal whenthe orientation of the device is changed. Reconfigurable antennas can be used get ridof this nuisance so that what ever be the orientation, the handheld device still gets thebest possible signal level. With our presented antenna, we can achieve up to sixteendifferent configurations depending upon the requirement. The differentconfigurations are controlled with the help of RF switches which are implementedusing micro-electromechanical systems (MEMS). The reconfigurable antenna wasfabricated and tested for its impedance and radiation characteristics and the resultswere found to be in reasonable agreement with the simulations.

  • 24.
    Mowlér, Marc
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Signal Processing.
    Larsson, Erik G.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Lindmark, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Ottersten, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Methods and bounds for antenna array coupling matrix estimation2007In: 2007 IEEE International Conference on Acoustics, Speech, and Signal Processing, IEEE , 2007, p. 881-884Conference paper (Refereed)
    Abstract [en]

    A novel method is proposed for estimation of the mutual coupling matrix of an antenna array. The method extends previous work by incorporating an unknown phase center and the element factor (antenna radiation pattern) in the model, and treating these as nuisance parameters during the estimation of coupling. To facilitate this, a parametrization of the element factor based on a truncated Fourier series is proposed. The Cramer-Rao bound (CRB) for the estimation problem is derived and used to analyze how the required amount of measurement data increases when introducing a more and more flexible model for the element factor. Finally, the performance of the proposed estimator is illustrated using data from measurements on an 8-element antenna array.

  • 25.
    Mowlér, Marc
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Lindmark, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Estimation of Coupling, Element Factor, and Phase Center of Antenna Arrays2005In: Antennas and Propagation Society International Symposium, 2005 IEEE, IEEE , 2005, p. 6-9Conference paper (Refereed)
    Abstract [en]

    A method for joint estimation of the coupling matrix, element factor, and phase center of an array from calibration data is proposed. Our simulation results for an 8 element array show that optimal compensation for an adaptive antenna is only achieved if all parameters are properly estimated.

  • 26.
    Mowlér, Marc
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Lindmark, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Reconfigurable MEMS Antenna for MIMO Applications2006Conference paper (Other academic)
    Abstract [en]

    A polarization reconfigurable PIFA with RF-MEMS switches is proposed as an antenna element for MIMO systems. Two different polarizations are achieved through the symmetrical design that incorporates RF-MEMS switches. Measurements and simulations are presented along with calculations on the correlation between the two configurations.

  • 27.
    Mowlér, Marc
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Lindmark, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Reconfigurable MEMS Antenna for Wireless Applications2006In: EuCAP 2006: proceedings of the European Conference on Antennas and Propagation, 6-10 November 2006, Nice, France, European Space Agency, 2006, p. 1-6Conference paper (Refereed)
    Abstract [en]

    A polarization reconfigurable PIFA with RF-MEMS switches is proposed as a mobile terminal antenna element for MIMO systems. Two different polarizations are achieved through the symmetrical design that incorporates RF-MEMS switches. Measurements and simulations are presented along with calculations on the correlation between the two configurations.

  • 28.
    Mowlér, Marc
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Lindmark, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Larsson, Erik G.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Ottersten, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Joint estimation of mutual coupling, element factor, and phase center in antenna arrays2007In: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, Vol. 2007, no 1, p. 030684-Article in journal (Refereed)
    Abstract [en]

    A novel method is proposed for estimation of the mutual coupling matrix of an antenna array. The method extends previous work by incorporating an unknown phase center and the element factor (antenna radiation pattern) in the model, and treating them as nuisance parameters during the estimation of coupling. To facilitate this, a parametrization of the element factor based on a truncated Fourier series is proposed. The performance of the proposed estimator is illustrated and compared to other methods using data from simulations and measurements, respectively. The Cramer-Rao bound (CRB) for the estimation problem is derived and used to analyze how the required amount of measurement data increases when introducing additional degrees of freedom in the element factor model. We find that the penalty in SNR is 2.5 dB when introducing a model with two degrees of freedom relative to having zero degrees of freedom. Finally, the tradeoff between the number of degrees of freedom and the accuracy of the estimate is studied. A linear array is treated in more detail and the analysis provides a specific design tradeoff.

  • 29.
    Mowlér, Marc
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Lindmark, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Oberhammer, Joachim
    KTH, School of Electrical Engineering (EES), Microsystem Technology.
    Stemme, Göran
    KTH, School of Electrical Engineering (EES), Microsystem Technology.
    A 2-bit reconfigurable meander slot antenna with RF-MEMS switches2005In: Antennas and Propagation Society International Symposium, 2005 IEEE: volym 2A, 2005, p. 396-399Conference paper (Refereed)
    Abstract [en]

    A novel antenna with two RF-MEMS switches placed symmetrically on an asymmetrical meander-shaped slot yielding four different operating frequencies is proposed. The final antenna was manufactured and the four different switching configurations were verified with dummy switches. The measured results were satisfying for all four frequencies with a return loss well above 10 dB. In addition, the actual switches were mounted on the antenna. This proved that the antenna properties are unaffected by the switches. Further use of additional switches on the same antenna is discussed in the paper.

  • 30.
    Nilsson, Martin
    et al.
    KTH, Superseded Departments (pre-2005), Signals, Sensors and Systems.
    Lindmark, Björn
    KTH, Superseded Departments (pre-2005), Signals, Sensors and Systems.
    Ahlberg, M
    Larsson, M.
    Beckman, Claes
    University of Gävle, Gävle (Sweden).
    Characterization of a Wideband Radio Channel using Spatio Temporal Polarization Measurements1999In: IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, 1999Conference paper (Refereed)
  • 31.
    Nilsson, Martin
    et al.
    KTH, Superseded Departments (pre-2005), Signals, Sensors and Systems.
    Lindmark, Björn
    Dep. of Electromagnetics, Chalmers University of Technology, Goteborg, Sweden.
    Ahlberg, Mikael
    Larsson, Mikael
    Beckman, Claes
    Measurements of the Spatio-Temporal Polarization Characteristics of a Radio Channel at 1800 MHz1999In: Proceedings IEEE Vehicular Technology Conference, IEEE , 1999, p. 386-391Conference paper (Refereed)
    Abstract [en]

    We present a combined measurement and analysis of the spatial, temporal, and polarisation characteristics of a 1800 MHz radio channel. The measurements were performed using a correlative channel sounder. A complex chirp signal with a bandwidth of 150 MHz was transmitted by a vertically polarized omnidirectional antenna and received by a 8+8 dual polarized planar antenna array. Measurements were taken at two different base station locations, one being suburban and the other urban. Using this data we characterize the radio channel in terms of azimuth and delay spread of the vertical and horizontal polarization.

  • 32. Pascaud, R.
    et al.
    Gillard, R.
    Loison, R.
    Wiart, J.
    Wong, M. F.
    Lindmark, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Garcia-Garcia, L.
    New DG-FDTD method: Application to the study of a MIMO array2007In: 2007 IEEE Antennas and Propagation Society International Symposium, IEEE , 2007, p. 3085-3088Conference paper (Refereed)
  • 33.
    Ribbenfjärd, David
    et al.
    KTH, Superseded Departments (pre-2005), Signals, Sensors and Systems.
    Lindmark, Björn
    KTH, Superseded Departments (pre-2005), Signals, Sensors and Systems.
    Karlsson, Bo
    Eklund, Lars
    Improved vehicle antenna system for measurement of 3G radio coverage2004In: Joint COST 273/284 Workshop on Antennas and Related System Aspects in Wireless Communications, 2004, p. 189-193Conference paper (Refereed)
  • 34.
    Ribbenfjärd, David
    et al.
    KTH, Superseded Departments (pre-2005), Signals, Sensors and Systems.
    Lindmark, Björn
    KTH, Superseded Departments (pre-2005), Signals, Sensors and Systems.
    Karlsson, Bo
    Eklund, Lars
    Omnidirectional Vehicle Antenna for Measurement of Radio Coverage at 2 GHz2004In: IEEE Antennas and Wireless Propagation Letters, ISSN 1536-1225, Vol. 3, no 1, p. 269-272Article in journal (Refereed)
    Abstract [en]

    To accurately determine radio coverage, it is necessary to have an omnidirectional antenna pattern. Our measurement results show that this is not the case for an antenna mounted on a vehicle. We present two improved antenna solutions with an additional ground plane in the form of a disk and a corrugated cone. The peak-to-peak variation in the horizontal plane is then reduced from 5 to 2.5 dB and 1.7 dB, respectively. Although our results are limited to a medium-size vehicle and frequencies around 2 GHz, we believe that they are of interest for all measurements where high accuracy is desired.

  • 35. Zervos, T.
    et al.
    Alexandridis, A.
    Peppas, K.
    Lazarakis, F.
    Dangakis, K.
    Soras, C.
    Lindmark, Björn
    KTH, Superseded Departments (pre-2005), Signals, Sensors and Systems.
    The influence of MIMO terminal user's hand on channel capacity2006Conference paper (Refereed)
    Abstract [en]

    In this paper the impact of user's hand holding a Multiple-Input-Multiple- Output (MIMO) terminal on the system performance is investigated. A 4×4 MIMO system is considered with a Personal Digital Assistant (PDA) terminal equipped with a compact array of 4 patch elements. The radiation patterns of the antenna elements are simulated in the presence of the other elements and in the presence of a user's hand. The obtained patterns are used to evaluate the covariance matrix of the receive antenna which is incorporated in a correlation-based MIMO channel model. MIMO channel capacity is calculated to demonstrate the capacity degradation caused by the user's hand.

1 - 35 of 35
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