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  • 1. Bantavis, P. I.
    et al.
    Kolitsidas, Christos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Empliouk, T.
    Le Roy, M.
    Jonsson, B. Lars G.
    KTH, School of Electrical Engineering and Computer Science (EECS), 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.

  • 2.
    Björkqvist, Oskar
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Dahlberg, Oskar
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Silver, Gustaf
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Kolitsidas, Christos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Quevedo-Teruel, Oscar
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Jonsson, B. Lars G.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Wireless Sensor Network Utilizing Radio-Frequency Energy Harvesting for Smart Building Applications2018In: IEEE Antennas & Propagation Magazine, ISSN 1045-9243, E-ISSN 1558-4143, Vol. 60, no 5, p. 124-136Article in journal (Refereed)
    Abstract [en]

    The scope of this article is to develop a modular radio-frequency (RF) energy-harvesting system for smart buildings that can act as a power source for sensing devices. Electromagnetic field-strength measurements at the main campus of the KTH Royal Institute of Technology in Stockholm, Sweden, were carried out to define the strength of the available ambient signals. Mainly two spectra were available for possible RF harvesting, i.e., two cellular bands [GSM1800 and third generation (3G)] and the 2.45-GHz Wi-Fi band. Based on these measurements, a modular approach for the system was adopted. The system is composed from two modules: 1) a Wi-Fi rectenna system composed of eight dual-polarized patch antennas and 16 rectifiers to produce eight differential voltage sources connected in series and 2) a cellular rectenna system composed of eight linear tapered slot antennas and eight rectifiers to produce four differential voltage sources connected in series. We propose an innovative multiple-input, single-output (MISO) wave rectifier that yields an efficient differential output. Both rectenna modules offer full azimuthal coverage and can operate either together or independently.

  • 3.
    Björkqvist, Oskar
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Kolitsidas, Christos
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Dahlberg, Oskar
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Silver, Gustaf
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Mattsson, M.
    Jonsson, B. Lars G.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    A Novel Efficient Multiple Input Single Output RF Energy Harvesting Rectification Scheme2017In: 2017 IEEE Antennas and Propagation Society International Symposium, Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 1605-1606Conference paper (Refereed)
    Abstract [en]

    In this work an implementation of an ambient radio frequency harvesting system utilizing multiple input single output approach is demonstrated. Measurements of typical ambient radiation have been conducted with respect to power levels and frequency to determine which communication signals are suitable for harvesting. The measurement campaign showed that the WiFi frequency band at 2.45 GHz is a good candidate for indoors applications. A Greinacher voltage doubler is used for the rectification. A multiple input single output - MISO scalable scheme approach is implemented that is able to provide a DC differential output voltage. Simulated and experimental results proved the MISO rectenna to be an efficient scheme for RF harvesting.

  • 4.
    Dahlberg, Oskar
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Kolitsidas, Christos
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Mattsson, M.
    Silver, Gustaf
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Björkqvist, Oskar
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Jonsson, B. Lars G.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    A Novel 32 Port Cube MIMO Combining Broadside and Endfire Radiation Patterns for Full Azimuthal Coverage - A Modular Unit Approach for a Massive MIMO System2017In: 2017 IEEE Antennas and Propagation Society International Symposium, Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 1641-1642Conference paper (Refereed)
    Abstract [en]

    In this paper we propose a novel 32 antenna port multiple-input-multiple-output (MIMO)-cube. The total volume of the cube is 320 x 320 x 120 mm(3) . On two faces, endfire radiating linear tapered slot antennas (LTSAs) are placed and on the remaining sides, a mix of both LTSAs and broadside patch antennas are placed. In total 16 LTSAs and 8 dual polarized patches are used. The LTSA is designed to operate at the GSM and 3G bands, from 1.7 to 2.3 GHz. A corrugation pattern is introduced along the edges of the LTSAs covering one face to increase directivity and decrease sidelobes. The LTSAs are placed in two different orientations in order to receive two polarisations. The patch antenna is dual band and dual polarized. It operates in the frequency bands 2.4-2.5 and 5.45-5.6 GHz where Wi-Fi communication is made. The spatial placement, with antennas on all sides of the cuboid, ensures full azimuthal coverage despite the high directivity of the antennas. Using different antennas on different faces of the cube further optimizes the volume efficiency of the cube for azimuthal coverage.

  • 5.
    Mattsson, Martin
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Kolitsidas, Christos
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Jonsson, B. Lars G.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Dual-Band Dual-Polarized Full-Wave Rectenna Based on Differential Field Sampling2018In: IEEE Antennas and Wireless Propagation Letters, ISSN 1536-1225, E-ISSN 1548-5757, Vol. 17, no 6, p. 956-959Article in journal (Refereed)
    Abstract [en]

    A dual-band rectenna for radio frequency (RF) energy harvesting is presented in this letter. The proposed antenna has two concentric square patches electrically connected with a small microstrip line connection. Four ports are located in the inner patch. The configuration of the ports enables a differential field sampling scheme and dual polarization. The antenna operates for the WiFi frequency bands of 2.4 and 5.5 GHz with 7.52 and 7.26 dBi gain, respectively, for each frequency. A full-wave Greinacher voltage doubler rectifier for each polarization has been employed for RF-to-dc conversion. The proposed novel topology utilizes the differential field sampling for each polarization and quadruples the overall output voltage by the rectification process. The differential output voltage source from the rectenna can directly act as a power source as typically electronics require differential source for their operation.

  • 6.
    Mattsson, Martin
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Kolitsidas, Christos
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Silver, Gustaf
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Björkqvist, Oskar
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Dahlberg, Oskar
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Jonsson, B. Lars G.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    A high gain Dual-Polarised Differential Rectenna for RF Energy Harvesting2017In: 2017 IEEE Antennas and Propagation Society International Symposium, Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 1609-1610Conference paper (Refereed)
    Abstract [en]

    A rectenna for radio frequency (RF) energy harvesting is presented in this paper. We introduce a novel technique for RF rectification that is based on differential field sampling and a Greinacher voltage doubler rectifier. The proposed rectification antenna is a dual polarized patch with 4 ports that operates for the WiFi frequency band of 2.4-2.5 GHz and has a gain of 6.75 dB at each port. The proposed novel topology doubles the amount of input power accepted for each polarization and then quadruples the overall output power. In addition we have a differential output voltage source that is typically required for the electronics connected to the harvesting system.

  • 7.
    Silver, Gustaf
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Kolitsidas, Christos
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Björkqvist, Oskar
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Matsson, M.
    KTH.
    Dahlberg, Oskar
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Jonsson, B. Lars G.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Exploiting Antenna Array Configurations for Efficient Simultaneous Wireless Information and Power Transfer2017In: 2017 IEEE Antennas and Propagation Society International Symposium, Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 1083-1084Conference paper (Refereed)
    Abstract [en]

    Different patch antenna array configurations for Simultaneous Wireless Information and Wireless Power Transfer - SWIPT - were simulated and evaluated. The scope of the work is to provide configurations that can be used to minimise the interference between information and power transfer as well as provide some beamforming capabilities. Our assumption for all the evaluated structures are that two receive antennas are used for RF energy harvesting and one antenna is used for information exchange. The choice for two antennas for energy harvesting is based on that a differential DC output full-wave rectifier is used. Our analysis is based on patch antennas.

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