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1.	Fager, Christian, 1974, et al. (författare) IC Design Aspects for 5G mm-Wave Systems 2020 Ingår i: 2020 50TH EUROPEAN MICROWAVE CONFERENCE (EUMC). - 2325-0305. - 9782874870590 ; , s. 870-871 Konferensbidrag (övrigt vetenskapligt/konstnärligt)
2.	Iupikov, Oleg, 1983, et al. (författare) A Cavity-Backed Patch Antenna with Distributed Multi-Port Feeding, Enabling Efficient Integration with Doherty Power Amplifier and Band-Pass Filter 2021 Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 69:8, s. 4412-4422 Tidskriftsartikel (refereegranskat)abstract A joint design approach for co-integrated antenna and power amplifier (PA), employing a high-efficiency Doherty PA (DPA) architecture and including a band-pass RF filter, is proposed. This design is realized through the optimally distributed and balanced multi-port feeding of the cavity-backed patch antenna element that provides the desired (unique) loading conditions for the main and auxiliary PA branches and tailored power combining. A novelty and advantage of this feeding solution is that each pair of feeding points form a virtual common feeding centre of the radiating element; as a result, the radiation pattern remains power invariant when the port excitations change. A joint optimization of the integrated antenna-DPA transmitter is carried out to enhance the overall performance and maximize the bandwidth. This optimization is demonstrated through an example design for the sub-6 GHz telecommunication applications that target high power-efficiency (>50%) at the 6dB backed-off power levels and require RF-filtering in a compact integrated design. The latter challenge leads to a non-conventional implementation, which generally does not require the filter to be inserted between the antenna and the final output stage of the PA, and can be embedded in the topology with complex-valued source/load impedance values. Results of numerical studies are supported by measurements obtained with the antenna-DPA-filter prototype system.
3.	Iupikov, Oleg, 1983, et al. (författare) A Dual-Fed PIFA Antenna Element With Nonsymmetric Impedance Matrix for High-Efficiency Doherty Transmitters: Integrated Design and OTA-Characterization 2020 Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 68:1, s. 21-32 Tidskriftsartikel (refereegranskat)abstract A single planar inverted F-antenna is proposed employing two input ports to optimally power-combine the output signals of two nonlinear power amplifiers inside the metal-only low-loss antenna structure. High power-added efficiency (PAE) at back-off power levels is reached through a Doherty combiner architecture, where the optimal power combination is seen to generally require the synthesis of a nonsymmetric antenna input impedance matrix. The dual-fed antenna is compact and exhibits close to single-mode radiation properties; it has a relatively stable gain pattern despite the nonequal Doherty power amplifier (PA) output powers. An integrated active prototype has been designed, fabricated, and characterized over-the-air in both an anechoic and a reverberation chamber. Good agreement is observed and an uncertainty analysis is performed. The Doherty transmitter features a max-PAE of 58 at 2.14 GHz and a 6 dB back-off PAE of 52; a minimum system power gain of 9.5 dB (max 12 dB); and a maximum system output power of 43.5 dBm.
4.	Aljarosha, Alhassan, 1982, et al. (författare) A Wideband Contactless and Bondwire-Free MMIC to Waveguide Transition 2017 Ingår i: IEEE Microwave and Wireless Components Letters. - 1558-1764 .- 1531-1309. ; 27:5, s. 437-439 Tidskriftsartikel (refereegranskat)abstract A contactless transition from a high-permittivity microstrip line (e_r=9.9) to an air-filled waveguide (WG) has been impedance-matched over a large simulated relative bandwidth of 38% (W-band, 75-110 GHz). The transition couples the EM fields directly from the MMIC's microstrip line via an SIW and an off-chip stub section to a ridge WG section. The novel structure is low loss and suits pick-and-place assembly techniques of mm-Wave MMICs inside metal WGs. The design process is detailed and manufacturing tolerances of the Alumina prototype PCB are discussed. The measured back-to-back structure retains an appreciable insertion loss smaller than 0.8 dB for a single transition and a fractional bandwidth of 28% (72-95~GHz) over which the return loss is greater than 10 dB.
5.	Aljarosha, Alhassan, 1982, et al. (författare) Mm-Wave contactless connection for MMIC integration in gap waveguides 2016 Ingår i: 2016 IEEE Antennas and Propagation Society International Symposium, APSURSI 2016, Fajardo, Puerto Rico, 26 June - 1 July 2016. - 1522-3965. ; , s. 253-254 Konferensbidrag (refereegranskat)abstract A contactless, broadband and low-loss microstrip-to-groove gap waveguide transition operating at W-band is presented. The principle of operation is based on transforming EM fields from the SIW to the ridge gap waveguide mode via electromagnetic coupling. This is advantageous, since the proposed solution avoids the use of metal contact between the SIW and one of the waveguide parts. Furthermore, metamaterial-based gap waveguide technology provides a resonance-free packaging solution.
6.	Aljarosha, Alhassan, 1982, et al. (författare) Performance Analysis of an Integrated Multi-Channel Power Amplifier Incorporating an IC-to-Waveguide Transition 2021 Ingår i: 2021 15TH EUROPEAN CONFERENCE ON ANTENNAS AND PROPAGATION (EUCAP). - 2164-3342. Konferensbidrag (refereegranskat)abstract This paper studies the power combiner efficiency of multiple Power Amplifier (PA) output signals that are combined within a low-loss contactless transition, intrinsically having low isolation characteristics. Since the PA performance is sensitive to load impedance variations, poor isolation may affect each PA performance, thereby reducing the overall power combiner efficiency. Load impedance variations can e.g. be due to process, supply-voltage and temperature variations. A four-way spatial power combiner (SPC) design is compared to an on-chip Wilkinson Power Combiner (WPC) implemented in 0.13 mu m SiGe BiCMOS technology incorporating a 50 Omega impedance matching network. The WPC occupies 84% more area than the non-isolating SPC. Moreover, the non-isolating SPC has an average efficiency 14% larger than the WPC. For physically realistic variations, simulated results show a sigma-variation of 2.81 mW in P-out and 0.87 % in PAE for the non-isolating SPC, and 2.34 mW in P-out and 0.45 % in PAE for the WPC (@1 dB compression).
7.	Aljarosha, Alhassan, 1982, et al. (författare) Performance comparison of silicon substrates for IC-waveguide integration based on a contactless transition at mm-wave frequencies 2019 Ingår i: 2019 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting, APSURSI 2019 - Proceedings. ; July 2019, s. 1081-1082 Konferensbidrag (refereegranskat)abstract This paper presents a comparison between different silicon (Si) substrates used in Si-based IC technologies at E-Band (71-86 GHz). A unique low-loss and compact contactless transition from a silicon IC (p-doped substrate) to a metal waveguide is used. The proposed transition incorporates a spatial power combiner to enable direct electromagnetic coupling from an array of patches on the IC to a metal waveguide. This design enables a high-power transition from an IC to a waveguide and/or antenna at millimeter-wave (mm-wave) frequencies, where a galvanic contact between the two parts is avoided.
8.	Aljarosha, Alhassan, 1982, et al. (författare) Silicon-Based IC-Waveguide Integration for Compact and High-Efficiency mm-Wave Spatial Power Combiners 2021 Ingår i: IEEE Transactions on Components, Packaging and Manufacturing Technology. - 2156-3985 .- 2156-3950. ; 11:7, s. 1115-1121 Tidskriftsartikel (refereegranskat)abstract A novel and compact millimeter-wave spatial power combiner is developed integrating a Silicon-based integrated circuit (IC) in a metal waveguide. As an initial step towards integrating a silicon-based active IC in a waveguide, a passive back-to-back transition incorporating a 4-way spatial power splitter and combiner is realized at E-band (71–86 GHz). In contrast to existing solutions, the proposed design considers power splitting and combining using a low-loss wireless transition between the IC and the waveguide. The proposed back-to-back structure comprises an IC implemented using Institute for High Performance Microelectronics (IHP’s) 0.13μm SiGe BiCMOS technology integrated into the H-plane of a waveguide. The IC is post-processed and assembled in the waveguide prototype. The measured prototype shows a return loss better than 13 dB, an average insertion loss of 1.7 dB for a single transition, and a fractional bandwidth of 26.4 % (69–90 GHz).
9.	Aljarosha, Alhassan, 1982, et al. (författare) Toward Wide-Band Low-Loss Gap-Waveguide-Integrated Grid Amplifiers 2017 Ingår i: 2017 International Symposium on Antennas and Propagation (ISAP). - 9781538604656 ; 2017-January Konferensbidrag (refereegranskat)abstract A passive W-band 19-channel spatial power splitter/combiner is presented, for the applications in grid amplifiers design. The design employs a linear array of chip-to-air-filled waveguide contactless connections, and are directly integrated within a single-layer. The meta-material-based gap waveguide is used; it enables a low-loss low-profile solution. The quasi optical beamformer gives rise to a parallel-plate planar waveguide field which excites an array of contactless chip-to-waveguide transitions via step-tapered ridge gap waveguides. The other beamformer restores the field distribution (after amplification) and excites a wave going towards the waveguide output. Furthermore, the gap waveguide technology isolates the amplifiers from one another and provides a packaging solution in a single unit. The simulated return loss of the back-to-back structure is larger than 12 dB, while the insertion loss is smaller than 1.2 dB over the entire W-band (75-110 GHz).
10.	Amani, Navid, 1985, et al. (författare) Array Configuration Effect on the Spatial Correlation of MU-MIMO Channels in NLoS Environments 2020 Ingår i: 14th European Conference on Antennas and Propagation, EuCAP 2020. ; 2020:March Konferensbidrag (refereegranskat)abstract In this paper, three different base-station antenna (BSA) configurations are compared in terms of inter-user spatial correlation in a two dimensional (2D) non-line-of-sight (NLoS) environment. The three configurations are: (i) a regular uniform linear array (ULA); (ii) a periodic sparse array; and (iii) an aperiodic sparse array. Electromagnetic modeling of the NLoS channel is proposed where scatterers are considered as resonant dipoles confined in clusters of scatterers (CoSs). While the probability of facing highly correlated user-equipments (UEs) in a multi-user multiple-input multiple-output (MU-MIMO) system is decreasing as the richness of mutipath increases, the sparsity (increased inter-element spacing) is seen to be capable of reducing this probability as well. This is due to the larger spatial variations experienced by the sparse array. Moreover, the results show that further improvement can be achieved by deploying an aperiodic distribution of antenna elements into the sparse antenna aperture.
11.	Amani, Navid, 1985, et al. (författare) MIMO Channel Capacity Gains in mm-Wave LOS Systems with Irregular Sparse Array Antennas 2017 Ingår i: APWC 2017. ; 2017-January Konferensbidrag (refereegranskat)abstract This paper investigates potential advantages of linear irregular sparse antenna arrays over their regular counterparts in a mm-wave line-of-sight (LOS) multiple-input multiple-output (MIMO) scenario. The comparison is based on numerical computations of MIMO eigenvalues of the corresponding channel matrices and the resulting channel capacity. Identical linear antenna arrays are assumed at the transmitter and the receiver sides. The compared regular and irregular arrays have an equal aperture length. Mutual coupling between elements within an array is assumed negligible due to the array sparsity. A 4×4 MIMO channel is studied, where we change the position of the two inner elements to obtain irregularly spaced arrays. It is shown that for some specific distances between TX and RX, the irregular array distribution can significantly improve the channel capacity in LOS. This observation opts for reconfigurable array designs.
12.	Amani, Navid, 1985, et al. (författare) MIMO-Sparse Radars for Enhanced DOA Estimation of Spatio-Temporal Correlated Sources 2019 Ingår i: Proceedings of the 2019 9th IEEE-APS Topical Conference on Antennas and Propagation in Wireless Communications, APWC 2019. ; , s. 243-246 Konferensbidrag (refereegranskat)abstract This paper investigates an enhanced direction-of-arrival (DOA) estimation problem of spatio-temporal correlated sources when a multiple-input multiple-output (MIMO) sparse radar is deployed. A virtual array with increased degrees-of-freedom (DOF) is realized within two steps by combining MIMO radar with the Khatri-Rao (KR) product approach. Since the final virtual array is a uniform linear array (ULA), a well-known spatial smoothing algorithm is applied to reinforce the rank of its covariance matrix. Meanwhile, the enhanced DOF results in a higher spatial resolution of the radar in the context of DOA estimation.
13.	Amani, Navid, 1985, et al. (författare) Multi-Panel Sparse Base Station Design with Physical Antenna Effects in Massive MU-MIMO 2020 Ingår i: IEEE Transactions on Vehicular Technology. - 0018-9545 .- 1939-9359. ; 69:6, s. 6500-6510 Tidskriftsartikel (refereegranskat)abstract A novel base station antenna (BSA) configuration is presented to mitigate degrading physical antenna effects in massive multiple-input multiple-output (MIMO) systems, while minimizing implementation complexities. Instead of using a commonly considered single antenna panel comprising of many elements covering a wide field-of-view (FOV) of 120 degrees, L tilted panels are used employing L times fewer elements and L times smaller FOV per panel. The spatial resolution of each panel is enhanced by employing sparse arrays with suppressed (grating-lobe) radiation outside its corresponding FOV. Therefore, more directive antenna elements can be deployed in each panel to compensate for the effective isotropic radiated power (EIRP) reduction. While sectorisation reduces the antenna gain variation in 120 degrees FOV, cooperation among multiple panels in downlink beamforming is seen to be capable of inter-panel interference suppression for sum-rate enhancement. A network model is used as a multi-user (MU) MIMO simulator incorporating both antenna and channel effects. It is shown that when the number of base station antennas is ten times the number of users, the average downlink sum-rate in pure line-of-sight (LOS), rich and poor multipath environments is increased up to 60.2%, 23% and 11.1%, respectively, by multi-panel sparse arrays applying zero-forcing (ZF) precoding.
14.	Amani, Navid, 1985, et al. (författare) Network model of a 5G MIMO base station antenna in a downlink multi-user scenario 2018 Ingår i: IET Conference Publications. - : Institution of Engineering and Technology. ; 2018:CP741 Konferensbidrag (refereegranskat)abstract A system level network model of a 5G base station antenna (BSA) with massive multiple-input multiple-output (MIMO) capabilities is presented that incorporates antenna mutual interaction and signal processing aspects. The combined transmitter-channel-receiver in such a system is modeled by cascading Z-matrices to interrelate the transmitter and receiver port voltages/ currents to one another. The developed model is then subjected to the zero-forcing (ZF) beamforming algorithm to compute the per-antenna transmit power for a specific minimum signal level at the receiver as well as the required BSA effective isotropic radiated power (EIRP). The presented initial results show that in a line-of-sight (LOS) environment the required EIRP to achieve a 1 Gbps bitrate user link in a 15-200 m coverage ranges from 25-48 dBm, which increases to 31-54 dBm after incorporating first-order mutual coupling effects among the BSA elements.
15.	Amani, Navid, 1985, et al. (författare) On the Sparsity and Aperiodicity of a Base Station Antenna Array in a Downlink MU-MIMO Scenario 2018 Ingår i: ISAP 2018 - 2018 International Symposium on Antennas and Propagation. Konferensbidrag (refereegranskat)abstract An application study into irregular sparse arrays (ISAs) is proposed to function as base station antennas (BSAs) in a mm-wave multi-user multiple-input multiple-output (MU-MIMO) system. The results show that the sum rate capacity of ISAs can be increased relative to regularly-spaced BSA arrays with half a wavelength element separation, especially for a high number of users. This is due to the narrower beams formed by the larger antenna apertures of sparse arrays. Furthermore, the aperiodic distribution of antenna elements alleviates the problem of grating lobes in sparse arrays and is seen to improve the average power consumption of power amplifiers at the same time.
16.	Amani, Navid, 1985, et al. (författare) Per-Antenna Power Distribution of a Zero-Forcing Beamformed ULA in pure LOS MU-MIMO 2018 Ingår i: IEEE Communications Letters. - 1558-2558 .- 1089-7798. ; 22:12, s. 2515-2518 Tidskriftsartikel (refereegranskat)abstract An analytical model is presented to determine the per-antenna power distribution of a beamformed M-element uniform linear array (ULA) as a base station antenna (BSA). The analysis assumes a single sector cell serving two user equipments (UEs) in a downlink multiuser multiple-input multiple-output (MU-MIMO) system employing zeroforcing (ZF) transmission. Determinative design parameters of the BSA configuration are identified. Afterwards, their effects on the power spread across the array are investigated when the positions of the users are random and they are uniformly distributed over the cell. It is shown that the power distribution across the ULA antenna aperture is a periodic function whose characteristics mainly depend on the angular separation of two UEs and the number of BSA elements. A significant variation between ULA input powers is seen to occur if the number of elements in the ULA is smaller than one period of this power distribution function. In order to mitigate the dynamic range of the power variation across the array, an upper bound for the inter-element spacing, depending on the field-of-view (FoV) of the BSA, is defined. It is shown that, in a 20-element ULA, increasing the inter-element spacing from 0.5-wavelength to 1.4-wavelength reduces the power variation from 19 dB to 10 dB for differentiating two close-by UEs with 1 degree angular separation.
17.	Amani, Navid, 1985, et al. (författare) Sparse Array Synthesis Including Mutual Coupling for MU-MIMO Average Capacity Maximization 2022 Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 70:8, s. 6617-6626 Tidskriftsartikel (refereegranskat)abstract A hybrid optimization algorithm including mutual coupling (MC) is proposed to synthesize an irregular sparse array (ISA) for average capacity maximization in a multi-user multiple-input multiple-output (MU-MIMO) system. The hybrid approach is composed of two phases to sub-optimally determine the location of a fixed number of omni-directional thin dipole antennas in an arbitrary sparse aperture via a diagonal antenna selection matrix. In Phase I, the problem is relaxed to a convex optimization by ignoring the MC and weakening the constraints. The output of Phase I is accounted as a reliable initial guess for the genetic algorithm (GA) in Phase II, which incorporates the MC effects through the coupling matrix and avoids the convex relaxation technique. The proposed approach outperforms the conventional GA with a random initial population, while it avoids trying several starting positions. Meanwhile, the undesirable appearance of grating lobes, due to the under-sampling, and the degrading MC effects are suppressed by aperiodicity. It is observed that, doubling the conventional inter-element spacing (half-wavelength) and finding the location of eight dipoles in a sparse aperture by the proposed method improves the average capacity by 3.27-11.9% when the number of users varies from two to eight and the signal-to-noise ratio (SNR) is 30dB.
18.	Amani, Navid, 1985, et al. (författare) Sparse Automotive MIMO Radar for Super-Resolution Single Snapshot DOA Estimation With Mutual Coupling 2021 Ingår i: IEEE Access. - 2169-3536 .- 2169-3536. ; 9, s. 146822-146829 Tidskriftsartikel (refereegranskat)abstract A novel sparse automotive multiple-input multiple-output (MIMO) radar configuration is proposed for low-complexity super-resolution single snapshot direction-of-arrival (DOA) estimation. The physical antenna effects are incorporated in the signal model via open-circuited embedded-element patterns (EEPs) and coupling matrices. The transmit (TX) and receive (RX) array are each divided into two uniform sparse sub-arrays with different inter-element spacings to generate two MIMO sets. Since the corresponding virtual arrays (VAs) of both MIMO sets are uniform, the well-known spatial smoothing (SS) algorithm is applied to suppress the temporal correlation among sources. Afterwards, the co-prime array principle between two spatially smoothed VAs is deployed to avoid DOA ambiguities. A performance comparison between the sparse and conventional MIMO radars with the same number of TX and RX channels confirms a spatial resolution enhancement. Meanwhile, the DOA estimation error due to the mutual coupling (MC) is less pronounced in the proposed sparse architecture since antennas in both TX and RX arrays are spaced larger than half wavelength apart.
19.	Amani, Navid, 1985, et al. (författare) Towards a Generic Model for MU-MIMO Analysis Including Mutual Coupling and Multipath Effects 2019 Ingår i: 13th European Conference on Antennas and Propagation, EuCAP 2019. ; 2019 Konferensbidrag (refereegranskat)abstract A network model which accounts for antenna mutual coupling and multipath effects in a wireless channel is proposed as a tool to qualitatively evaluate the performance of a multi-user multiple-input multiple-output (MU-MIMO) system. The system performance is assessed when a zero-forcing (ZF) beamformed conventional uniform linear array (ULA) and a sparse array are employed as one sector of a base station antenna (BSA) in a single-cell network. It is shown that highly correlated user equipments (UEs) in a line-of-sight (LOS) scenario can be decorrelated to some extents, by a scattering environment in a non-line-of-sight (NLOS) scenario. This occurs due to increase of the spatial variation by a multipath effect. Furthermore, in both environments a sparse array realized by an increased interelement spacing is also capable for correlation reduction among users due to the narrower beams.
20.	Arts, M. J., et al. (författare) Analysis of the EMBRACE aperture array antenna by the characteristic Basis Function Method 2011 Ingår i: Proceedings - 13th International Conference on Electromagnetics in Advanced Applications, ICEAA'11, Torino, 12-16 September 2011. - 9781612849782 ; , s. 959-962 Konferensbidrag (refereegranskat)abstract This paper describes the use of the Characteristic Basis Function Method for the simulation of large phased array antennas for radio astronomy. It will be shown how the antenna effective area and the receiver noise temperature depend on array size. Also the receiving sensitivity Aeff /T sys normalised with respect to the physical area of the array will be shown for different array sizes and scan angles.
21.	Ayebe, Mustafa, 1997, et al. (författare) Systematic Self-Interference Mitigation in Full Duplex Antenna Arrays Via Transmit Beamforming 2023 Ingår i: 2023 International Conference on Electromagnetics in Advanced Applications, ICEAA 2023. ; , s. 158-163 Konferensbidrag (refereegranskat)abstract The optimal antenna array excitation vector is derived that maximizes the (realized) array gain in a particular direction while preventing the coupled input power to the low-noise amplifiers on the receive side to exceed a certain maximum threshold level. This is very useful for in-band full-duplex systems where the hardware complexity for self-interference cancellation must be minimized. In this approach, the perfect nulling of interference on the RX side is not required, sparing degrees of freedom for the TX beamformer. We evaluate the performance of the proposed TX beamforming algorithm by showing numerical results of the 25 x-polarized TX and 25 RX with 0.5λ element spacing and λ gap distance between the TX and RX sub-array.
22.	Bencivenni, Carlo, 1986, et al. (författare) A Simple Method for Optimal Antenna Array Thinning Using a Broadside MaxGain Beamformer 2013 Ingår i: 7th European Conference on Antennas and Propagation, EuCAP 2013, Gothenburg, Sweden, 8-12 April 2013. - 2164-3342. - 9788890701832 ; , s. 1799-1802 Konferensbidrag (refereegranskat)abstract A simple and effective method for optimal antenna array thinning employing a broadside-scanned maximum gain beamformer is presented. Starting from a fully populated λ/2-spaced regular lattice, the array is thinned by progressively 'turning off' the element(s) with the lowest weight(s) of the weight vector realizing maximum gain. The accuracy and effectiveness of the method is validated against a rigorous combinatorial search method that can be used to find the optimal irregular array configuration solution in small to moderate-sized arrays. Furthermore, to evaluate the robustness of the proposed approach, the effects of beam steering have been investigated for linear arrays consisting of 10-40 antenna elements as well. Good results can be obtained for close to broadside scanned arrays, which is of importance for the directly radiating arrays that are currently being considered as modern satellite systems.
23.	Bencivenni, Carlo, 1986, et al. (författare) Aperiodic Array Antennas for Future Satellite Systems 2014 Ingår i: Swedish Microwave Days March 11-12, 2014, Gothenburg, Sweden. Konferensbidrag (refereegranskat)abstract Today, most satellite systems employ reflector antennas to generate narrow beams covering a certain area of Earth’s surface from orbit. However, the performance specification of modern communication systems require an increasing demand on the multi-beam, multi-channel, dual-polarization and beam shaping capabilities, which renders the design of such complex systems to a major challenge.A worldwide view is that Direct Radiating Arrays (DRAs) will be part of the future satellite systems. DRAs can handle these complexities, but the design solutions, based on conventional regular arrays are expensive due to a large number of required array elements (100-1000 in dense array for geosynchronous orbit) and active components, such as low noise and power amplifiers. For this reason, aperiodic or sparse arrays, where the array layout is optimized, constitute a very attractive solution for minimizing the number of elements and thus the cost.To design aperiodic arrays, Array Signal Processing (ASP) based methods are commonly used, which are advantageous when optimizing for complex antenna beam specifications [1-2], but often assume idealized antenna elements (e.g. isotropic radiators or uniform field apertures) while ignoring antenna mutual coupling and edge truncation effects. Electro-Magnetic Simulations (EMS) overcome these drawbacks [3], but their use is limited to simplistic ASP schemes. Due to extreme computational demands, such methods are primarily used to evaluate beam performance degradation effects, but do not incorporate sparse array ASP design procedures, and hence, these approaches result in suboptimal solutions. Our aim is to enhance the current methodology by accounting for realistic elements and critical array effects in a rigorous numerical manner, while adapting advanced ASP algorithms for fulfilling the required specifications
24.	Bencivenni, Carlo, 1986, et al. (författare) Aperiodic Isophoric Slotted Waveguide Antenna for Point-to-Point Communications at Ka-band 2017 Ingår i: 2017 INTERNATIONAL SYMPOSIUM ON ANTENNAS AND PROPAGATION (ISAP 2017). - 9781538604656 ; 2017-January Konferensbidrag (refereegranskat)abstract We report the intermediate results on a novel slotted waveguide antenna for point-to-point communications at Ka band. The antenna adopts an aperiodic layout with uniformly excited elements capable of meeting the ETSI class II radiation pattern envelop in all planes with high aperture efficiency. A total of 16 regular waveguide subarrays with an aperiodic inter-column spacing along the E-plane are fed by a corporate feed network located underneath. The prototype was milled in three layers of aluminum and bonded by vacuum brazing. Measurements confirm a 15% impedance bandwidth. The simulated patterns satisfy the radiation pattern envelop and have a gain above 28.5 dBi over 29-31 GHz, corresponding to an efficiency better than 80%.
25.	Bencivenni, Carlo, 1986, et al. (författare) Aperiodic Switched Array for Line-of-Sight MIMO Backhauling 2018 Ingår i: IEEE Antennas and Wireless Propagation Letters. - 1548-5757 .- 1536-1225. ; 17:9, s. 1712-1716 Tidskriftsartikel (refereegranskat)abstract A switchable aperiodic array solution is proposed to increase the minimum channel capacity of a multiple-input-multiple-output (MIMO) backhauling system over an extended line-of-sight communication range. The objective is to propose a low-complexity design solution that is cost-effective in regard to the manufacturing, installation, and its design process. It is shown that by adding only one switch and one auxiliary antenna per base station, a 4 × 4 MIMO system can be realized that is capable of minimizing the capacity loss that both regular and aperiodic arrays suffer from as a function of the link distance.
26.	Bencivenni, Carlo, 1986, et al. (författare) Application of the Compressive-Sensing Approach to the Design of Sparse Arrays for SATCOM Applications 2016 Ingår i: Swedish Microwave Days, March 15-16, Linköping. ; 2016, s. 114- Konferensbidrag (refereegranskat)abstract Current SATCOM systems employ multiple reflectors with a one-feed-per-beam configuration to synthesize narrow spot-beams. However, these systems are very complex and offer very limited reconfigurability. Active antenna arrays are attractive solutions [1], although are often expensive due to the large number of elements and electronic components involved. Aperiodic array antennas can substantially reduce the number of elements and costs with respect to regular arrays but their design is challenging [2]. Several synthesis methods have been proposed, yet aperiodic array design techniques are not as mature as those in use for their regular array counterparts. These methods are often either: (i) accurate but computationally expensive (e.g. Genetic Algorithms [3]), or; (ii) efficient but simplified (e.g. Density Tapered method [4]). Compressive Sensing (CS) has been recently applied to the synthesis of sparse antenna arrays. The method can optimize large maximally sparse antenna array problems in a fast, deterministic and flexible way [5]. In previous research publications, the authors have (i) extended the original formulation to the multi-beam scenario; (ii) exploited array layout symmetry and modular design; and (iii) hybridized the original iterative optimization procedure with a full-wave EM analysis, so as to include the effects of mutual coupling into the design process and studied for arrays of strongly coupled antennas elements, such as dipoles, as well as large planar arrays of pipe horns [6, 7]. Additionally the authors have addressed multi element type design [8] and, more recently, are investigating reconfigurable arrays (i.e. arrays designed to provide a set of arbitrary-shaped beams) and isophoric arrays (i.e. arrays with a single excitation amplitude). The main directions are summarized in Fig. 1.
27.	Bencivenni, Carlo, 1986, et al. (författare) Design of Maximally Sparse Antenna Arrays in the Presence of Mutual Coupling 2015 Ingår i: IEEE Antennas and Wireless Propagation Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 1548-5757 .- 1536-1225. ; 14, s. 159-162 Tidskriftsartikel (refereegranskat)abstract An optimization framework is proposed that combines electromagnetic field simulations with an iterative l(1)-norm minimization procedure to synthesize optimally sparse antenna arrays. The proposed approach overcomes the limitation of design methodologies that assume idealized antenna elements employing equal (isolated or isotropic) element patterns, as these yield suboptimal solutions when the antenna mutual coupling effects cannot be ignored. The latter is demonstrated for arrays of relatively strongly coupled dipole radiators.
28.	Bencivenni, Carlo, 1986, et al. (författare) Effects of Regular and Aperiodic Array Layout in Multi-User MIMO Applications 2017 Ingår i: IEEE Antennas and Propagation Society International Symposium. - 1522-3965. - 9781538632840 ; 2017-January, s. 1877-1878 Konferensbidrag (refereegranskat)abstract In MIMO applications, antenna arrays adopt a uniform regular lattice. However, in phased array applications, it is a well-known fact that aperiodic or irregular arrays can offer several advantages. In this paper, we present initial investigations on the effects of regular and aperiodic layouts in Multi-User MIMO applications. We aim at explaining and providing an intuitive understanding on why aperiodic arrays are superior to regular ones. Additional results and quantification of the advantages will be presented in an upcoming journal publication.
29.	Bencivenni, Carlo, 1986, et al. (författare) Multi-Element Aperiodic Array Synthesis by Compressive Sensing 2015 Ingår i: ICEAA 2015. - 9781479978069 ; , s. 223-226 Konferensbidrag (refereegranskat)abstract In recent years, Compressive Sensing has attracted considerable attention in various areas of antennas and electromagnetics, including the synthesis of sparse array antennas. The CS synthesis of arrays achieves higher accuracy than analytical methods and allows for the fast and deterministic design of large complex arrays, without resorting to computationally expensive Global Optimization methods. The CS approach presented here has been previously studied by the authors for the design of maximally sparse arrays in the presence of mutual coupling effects, beam scanning degradation, as well as the imposition of symmetries for design modularity. In this manuscript the authors demonstrate another (yet unexplored) capability of such an approach, i.e., to incorporate different element types and determine their optimum combination in the course of the array synthesis procedure. Numerical examples are illustrated for large arrays comprising uniform circular aperture elements and operating in a SATCOM multi-beam scenario. It is shown that by exploiting this capability it is possible to simultaneously reduce the number of elements and gain scan loss.
30.	Bencivenni, Carlo, 1986, et al. (författare) Reconfigurable aperiodic array synthesis by Compressive Sensing 2016 Ingår i: 2016 10th European Conference on Antennas and Propagation, EuCAP 2016. - 9788890701863 Konferensbidrag (refereegranskat)abstract Aperiodic arrays represent an attractive technology for applications requiring multiple pencil beams or contour beams, such as in radars, satellite communication and mw-sensor systems. These antennas are typically designed to either produce high-directivity beams over a given scan range or a single beam with a specified complex shape. In this manuscript we present a CS approach for the synthesis of a single aperiodic array layout capable of radiating multiple beams with different shapes The approach aims at designing reconfigurable arrays with least number of elements as well as the optimal excitation set for each of the desired beams. Preliminary results for an array providing both pencil and a flattop coverage are presented.
31.	Bencivenni, Carlo, 1986, et al. (författare) Synthesis of circular isophoric sparse arrays by using compressive-sensing 2016 Ingår i: 2016 IEEE Antennas and Propagation Society International Symposium, APSURSI 2016 - Proceedings. - 9781509028863 ; , s. 761-762 Konferensbidrag (refereegranskat)abstract A design approach for large-scale sparse arrays based on Compressive Sensing has been recently introduced in the literature and extended to include complex EM effects and scan performance. However, that approach cannot directly control the number of excitation amplitudes. Here, we apply a two-step procedure that first synthesizes continuous rings with unconstrained amplitudes using an iterative ℓ1-norm minimization approach, and then replaces them with a circular isophoric ring array with a number of elements proportional to the original amplitude of each ring. The procedure is demonstrated for an isotropic array of a 10λ radius, for which a reference solution based on the analytical density-taper approach is available in the literature. Results show the capability of the proposed method to achieve a significant reduction of the array aperture (20%) with 25% less elements or 4dB lower peak side lobe level.
32.	Bencivenni, Carlo, 1986, et al. (författare) Synthesis of Maximally Sparse Arrays Using Compressive Sensing and Full-Wave Analysis for Global Earth Coverage Applications 2016 Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 64:11, s. 4872-4877 Tidskriftsartikel (refereegranskat)abstract Global optimization methods can be employed to design aperiodic array antennas that accurately account for their electromagnetic (EM) behavior and complex performance specifications. However, they are computationally expensive and, therefore, limited to small to midsized array problems. On the other hand, analytical methods do not suffer from this problem, but often assume idealized antenna elements and fully adjustable excitation controls, thereby excluding beam degradation effects caused, e.g., by mutual coupling (MC) and quantized phase shifters. We present a fast design method for large maximally sparse arrays that is capable of handling the aforementioned limitations. It is based on the previously published combined EM-Compressive Sensing approach, which has been herein generalized for multibeam optimization, and where we also exploit array symmetry in order to reduce the design complexity. Results are obtained for a circular array ( 100 λ diameter) of horn antennas operating in a multibeam SATCOM scenario, and demonstrate that even weak MC effects and small phase quantization are important when very demanding sidelobe and cross-polarization levels are required.
33.	Benthem, P., et al. (författare) Aperture array development for future large radio telescopes 2011 Ingår i: European Conference on Antennas and Propagation 2011, 11-15 April 2011, Rome. Konferensbidrag (refereegranskat)abstract We present the design of a phased array system for future radio telescopes. This includes a system overview and recent results of the designed and implemented system, the Electronic Multi-Beam Radio Astronomy Concept (EMBRACE). Furthermore, simulations with a full-EM antenna simulator, combined with measurements on actual hardware, will provide information for the next design step, the Aperture Array Verification System (AAVS). With AAVS, we will prove design readiness of this novel array technology.
34.	Beukman, Theunis S., 1986, et al. (författare) A Quadraxial Feed for Ultra-Wide Bandwidth Quadruple-Ridged Flared Horn Antennas 2014 Ingår i: 8th European Conference on Antennas and Propagation, EuCAP 2014, The Hague, The Netherlands 6-11 April 2014. - 2164-3342. - 9788890701849 ; , s. 3312 - 3316 Konferensbidrag (refereegranskat)abstract A quadraxial feed, excited by two orthogonal differential modes, is proposed for ultra wideband quadruple-ridged flared horn (QRFH) antennas that obviates the need for a balun. It is shown that in this configuration the fundamental TE11 mode is most strongly excited over the entire frequency band, while the higher-order modes are significantly suppressed, as compared to the conventional excitation using the ridge-to-coax balun transition. These properties lead to several advantages for QRFH antenna applications which require frequency-invariant beam characteristics, high port isolation and low cross-polarisation level, such as e.g. reflector antenna feeds for future radio telescopes.
35.	Beukman, T. S., et al. (författare) Equivalent Circuit of a Quadraxial Feed for Ultra-Wide Bandwidth Quadruple-Ridged Flared Horn Antennas 2015 Ingår i: 9th European Conference on Antennas and Propagation, EuCAP 2015, Lisbon, Portugal, 13-17 May 2015. - 9788890701856 Konferensbidrag (refereegranskat)abstract An equivalent circuit model of a quadraxial feed for ultra-wide bandwidth quadruple-ridged flared horn (QRFH) antennas is presented. The circuit is synthesised by only 3 unknowns and achieves an accurate input impedance for a wide range of dimensions. This model allows fast synthesis of optimal feeding designs that would ensure the excitation of the fundamental mode at the input of a QRFH.
36.	Beukman, T. S., et al. (författare) Modal-Based Design of a Wideband Quadruple-Ridged Flared Horn Antenna 2016 Ingår i: IEEE Transactions on Antennas and Propagation. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-926X .- 1558-2221. ; 64:5, s. 1615-1626 Tidskriftsartikel (refereegranskat)abstract In this paper, a systematic design technique for quadruple-ridged flared horn antennas is presented, to enhance the radiation properties through the profiling of the ridge taper. The technique relies on control of the cutoff frequencies of specific modes inside the horn, instead of brute-force optimization. This is used to design a prototype antenna as a feed for an offset Gregorian reflector system, such as considered for the Square Kilometer Array (SKA) radio telescope, to achieve an optimized aperture efficiency from 2 to 12 GHz. The antenna is employed with a quadraxial feeding network that allows the excitation of the fundamental TE11 mode, while suppressing all other modes that causes phase errors in the aperture. Measured results confirm the validity of this approach, where good agreement is found with the simulated results.
37.	Beukman, T. S., et al. (författare) Modal considerations for synthesizing the tapering profile of a quadruple-ridged flared horn antenna 2014 Ingår i: Proceedings - 2014 International Conference on Electromagnetics in Advanced Applications, ICEAA 2014. - 9781467357104 ; , s. 488-491 Konferensbidrag (refereegranskat)abstract A technique is proposed to synthesize the ridge taper of a quadruple-ridged flared horn (QRFH) antenna. By considering the modal propagation in the horn it is possible to improve the antenna performance. A QRFH is designed for an offset Gregorian reflector system and produces an aperture efficiency above 50% across the entire operational bandwidth (6:1).
38.	Bressner, Thomas A.H., et al. (författare) Cell Partitioning Antenna System Performance in Multi-User Scenarios for mmWave Communications 2021 Ingår i: IEEE Access. - 2169-3536 .- 2169-3536. ; 9, s. 127141-127149 Tidskriftsartikel (refereegranskat)abstract Fixed-beam, high-gain antenna systems can be used for a finer partitioning of the currently used cell-sectoring. This partitioning has the benefit of reducing the number of users seen per antenna beam, which reduces interference. Furthermore, the high antenna gain allows for a high effective isotropic radiated power while keeping the transmit power low. In this paper, we study the performance of such a fixed-beam, high gain antenna system design for millimeter-wave mobile communications. The antenna system is designed to keep the inter-sector interference in a multi-site scenario low. The performance is analyzed for single- and multi-user environments. In single-input single-output mode, the 50th percentile of the signal-to-interference-plus-noise ratio lies between 12.5 dB to 39.7 dB if 3 to 0 interferers are present, respectively. For multiple-input multiple-output transmission using zero-forcing, the signal-to-interference-plus-noise ratio increases and the 50th percentile ranges from 36.1 dB to 43.3 dB if 3 to 0 interferes are present, respectively. By using maximum ratio transmission, the best performance is achieved with no interferers present, while a plunge in performance is observed with interferers. Furthermore, the study revealed that the narrow beam antenna system can also provide a clear signal separation for small spatial separations. In the given example, the signal-to-interference-plus-noise ratio is larger than 32.1 dB with 11 active antenna elements, where 2.8 meters separate the users. Hence, the paper shows that the cell-partitioning antenna systems provide coverage in the desired area while keeping the inter-sector interference low, and the considered transmission techniques can be used for situation optimized mobile communication links.
39.	Buck, David, et al. (författare) Measuring Array Mutual Impedances Using Embedded Element Patterns 2023 Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 71:1, s. 606-611 Tidskriftsartikel (refereegranskat)abstract The radiation pattern of an antenna element embedded in a multiport antenna such as a phased array depends on the loads connected to the array element ports. If the embedded element patterns are measured using at least two known loading conditions, the patterns can be used to determine the array mutual impedance matrix. In previous work, this result has been derived with the simplifying assumption that the impedance of the source connected to the driven element changes along with the load impedances connected to the nondriven elements. In a practical test configuration, the source impedance cannot be readily changed. We analyze the case of EEPs measured with a fixed source impedance and changing impedances on the nondriven elements. The transformation from one set of EEPs to another with fixed source impedance is more complex than in the case of a source impedance that changes with the load impedances. The transformation depends on the coupling between elements and is only weakly sensitive to the element self-impedances. With measured EEPs for an array of identical elements, the impedance matrix can be found up to a scale factor. We demonstrate the method experimentally by measuring the patterns of an antenna array terminated with one loading condition and repeating the pattern measurements with a different loading condition. The mutual impedance matrix extracted from the pattern measurements compared to network analyzer mutual impedance measurements is accurate to within 1–2 Ω for most of the mutual impedances.
40.	Craeye, C., et al. (författare) Macro Basis Function Framework for Solving Maxwell’s Equations in Surface Integral Equation Form 2014 Ingår i: The FERMAT Journal. ; 3, s. 1-16 Tidskriftsartikel (refereegranskat)abstract The Macro Basis Functions (MBFs) approach is aform of domain-decomposition method applied to radiation andscattering problems solved by using integral-equation techniques.It enables a systematic reduction of the number of degrees offreedom, from that imposed by the discretization of the surfacesto that associated with the physical limits of field distributions.This paper reviews different variants of this approach, includingthe techniques for determining the MBFs and for fast calculationof their interactions. The link with Krylov-subspace iterativemethods is described, the relationship between the surface ofsubdomains and the number of physical degrees of freedom isdiscussed and multi-level schemes are revisited. Finally, avenuesfor further research are outlined in the Conclusions section ofthis paper.
41.	de Villiers, Dirk I. L., et al. (författare) Element Pattern Prediction in Mutually-Coupled Arrays Through Isolated Antenna Characterization 2017 Ingår i: 2017 INTERNATIONAL SYMPOSIUM ON ANTENNAS AND PROPAGATION (ISAP 2017). - 9781538604656 ; 2017-January Konferensbidrag (refereegranskat)abstract A simple method is proposed that is capable of predicting antenna array embedded element patterns based on the radiation and scattering characteristics of a single isolated antenna element. The effect of mutual coupling, which causes embedded element patterns to differ, is accounted for through the multi scattering of electromagnetic fields between array elements. This is a post-processing step and therefore obviates the need to run time-consuming full-wave electromagnetic field simulations, which is particularly important when numerous antenna array configurations need to be analyzed rapidly. The accuracy of three single-scattering versions of the pattern prediction method are evaluated on a range of two-element dipole arrays.
42.	de Villiers, D. I. L., et al. (författare) Fast Prediction of Aperture Efficiency and Sidelobe Levels in Shaped Reflector Systems through Model Based Output Space Mapping 2015 Ingår i: 9th European Conference on Antennas and Propagation, EuCAP 2015, Lisbon, Portugal, 13-17 May 2015. - 9788890701856 Konferensbidrag (refereegranskat)abstract This paper presents a fast method to accurately predict the aperture efficiency and sidelobe levels of shaped dual reflector systems over a wide region of the shaping parameter space. Only a few full evaluations of the system, at different points in the shaping parameter space, are needed to construct the model used for the predictions. The output space mapping technique is used to correct the responses obtained from a simple geometric optics model of the system for any desired point in the shaping parameter space by using the expected aperture edge taper information available from the shaping mapping and the feed pattern. The method is evaluated for a range of feeds, frequencies, and parameter spaces and shown to provide significantly improved results over the geometric optics predictions, while being orders of magnitude faster than full wave or asymptotic methods
43.	Elsakka, Amr, et al. (författare) A mm-Wave Phased-Array Fed Torus Reflector Antenna with ±30° Scan Range for Massive-MIMO Base-Station Applications 2022 Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 70:5, s. 3398-3410 Tidskriftsartikel (refereegranskat)abstract A phased-array fed reflector antenna system is presented which can be used for mm-wave base station applications. The proposed system is designed to support massive-Multi-Input-Multi-Output (MIMO) scenarios within a wide coverage (±30°) in the azimuth plane and a limited coverage at the elevation plane. A design and characterization methodology has been established to optimize the system for the operation in various line-of-sight conditions by adopting the maximum-ratio-transmission (MRT) and zero-forcing (ZF) MIMO algorithms. A two-user MIMO case study has been considered for the evaluation of the key system performance metrics, i.e. the effective isotropic radiated power, power consumption, signal-to-noise-ratio (SNR), and signal-to-interference-plus-noise-ratio (SINR). This study demonstrates that the phased-array fed reflector concept has a major advantage over traditional direct-radiating phased array (DRPA) antennas to reduce energy consumption. In the present example, it requires 12–14 dB less transmitted power as compared to the MRT-beamformed DRPAs for the same SNR, and 26–27 dB less transmitted power relatively to ZF-beamformed DRPA systems for the same SINR. A prototype, employing a 55 cm diameter torus reflector and operating at 28 GHz-band, has been manufactured and tested. The measurement results agree well with simulations.
44.	Farsaei, A., et al. (författare) On the Outage Performance of Line-Of-Sight Massive MIMO with a Fixed-Length Uniform Linear Sparse Array 2019 Ingår i: Proceedings of the 2019 9th IEEE-APS Topical Conference on Antennas and Propagation in Wireless Communications, APWC 2019. ; , s. 345-348 Konferensbidrag (refereegranskat)abstract Increasing the inter-element spacing of a uniform linear sparse array results in reducing the mutual coupling and simplifying the heat dissipation control of the array. However, increasing the inter-element spacing may result in the appearance of grating lobes in the field-of-view (FoV). In this paper, 0.05-outage capacity is used as the performance metric to optimize the inter-element spacing for a given array size in line-of-sight scenarios. For the case of two users, we propose to increase the inter-element spacing as long as the 0.05-outage capacity does not reduce more than 1% compared to the capacity achieved when the two users have orthogonal channel vectors. Radiated power at the base station is adjusted to have the same effective isotropic radiated power for different arrays. Simulation results for an array size of 40λ show that for FoVs of 60° to 120°, the inter-element spacing can be increased from 0.5λ to more than 1.14λ.
45.	Farsaei, Amirashkan, et al. (författare) Uniform Linear Arrays With Optimized Inter-Element Spacing for LOS Massive MIMO 2021 Ingår i: IEEE Communications Letters. - 1558-2558 .- 1089-7798. ; 25:2, s. 613-616 Tidskriftsartikel (refereegranskat)abstract In this letter, a uniform linear array (ULA) is proposed for line-of-sight massive multiple-input-multiple-output (MIMO). It is assumed that the number of antennas is fixed. For a given ULA with an arbitrary inter-element spacing, the probability that the correlation among the channel vectors of two users being above a threshold value is derived. The inter-element spacing of the proposed ULA is the one for which the aforementioned probability is minimized. To show the effectiveness of the proposed ULA, simulation results for two scenarios are given for a 64-antenna ULA that serves 6 single-antenna users. By using the proposed ULA instead of conventional half-wavelength ULA, 5th percentile sum-rate for zero-forcing precoder is improved by 9.90 bits/channel use in first scenario without dropping, and by 1.43 bits/channel use in second scenario with dropping 1 user.
46.	Glazunov, Andres Alayon, 1969, et al. (författare) Capacity Gains of (3 × 3)×(3 × 3) MIMO Fixed Links with Planar Aperiodic Sparse Arrays in Pure-LOS Channels 2018 Ingår i: Proceedings of the 2018 8th IEEE-APS Topical Conference on Antennas and Propagation in Wireless Communications, APWC 2018. ; , s. 734-736 Konferensbidrag (refereegranskat)abstract © 2018 IEEE. Presented is an analysis of the topology of a 3 × 3 element planar (square) array antenna with vertically polarized isotropic antenna elements. The focus has been on fixed multiple-input multiple-output communication links in pure line-of-sight channels. An empirical equation is presented for the mid-elements' relative position on the sides of the square array achieving near-optimal (3 × 3) × (3 × 3) multiple-input multiple-output capacity. It is observed that the position is a function of both the separation distance between transmit and receive antennas and the wavelength of the transmit signal in a similar way as for 3 × 3 systems with linear arrays. The capacity gains of the aperiodic planar array over the uniform planar array antenna configurations are presented. It is shown that considerable capacity gains in capacity can be obtained by choosing the right array topology following a simple design rule.
47.	Glazunov, Andres Alayon, 1969, et al. (författare) Emulating Rician distributed channels in a hybrid chamber for OTA measurements 2021 Ingår i: 2020 International Symposium on Antennas and Propagation, ISAP 2020. ; , s. 549-550 Konferensbidrag (refereegranskat)abstract It has been shown by means of simulations that the rich isotropic multipath and the random line-of-sight channels and other Rician channels in-between can be successfully generated in the same over-the-air hybrid measurement chamber without the use of additional static or moving scatterers.
48.	Glazunov, Andres Alayon, 1969, et al. (författare) Multipath Rician Channel Simulation in the Test Zone of a Hybrid OTA Chamber 2021 Ingår i: 15th European Conference on Antennas and Propagation, EuCAP 2021. Konferensbidrag (refereegranskat)abstract Multipath fields with ascribed Rician distribution parameters have been simulated in a novel hybrid chamber for over the air characterization of antenna systems and wireless devices. Simulations are based on waveguide mode summations representing a combination of the half-space rich isotropic multipath component and the on-axis line-of-sight component. It has been shown that the Rician distributed channels can be emulated without the use of additional static or moving scatterers.
49.	Glazunov, Andres Alayon, 1969, et al. (författare) Point-to-Point 3 x 3 MIMO Performance Gains with Aperiodic Sparse Arrays in Pure LOS Channels 2017 Ingår i: 2017 INTERNATIONAL SYMPOSIUM ON ANTENNAS AND PROPAGATION (ISAP 2017). - 9781538604656 ; 2017-January Konferensbidrag (refereegranskat)abstract Analyzed is the topology of a 3-element linear array antenna with vertically polarized isotropic antenna elements. The focus has been on point-to-point (PtP) multiple-input multiple output (MEMO) communication over pure line-of-sight (LOS) channels. An empirical equation is presented for the mid element's relative position achieving near-optimal 3 x 3 MIMO capacity. The position is a function of the transmit and the receive antennas separation distance and the wavelength of the transmit signal. The capacity gains of aperiodic over uniform array antenna configurations are presented, which at some distances can be a factor 2.5.
50.	Glazunov, Andres Alayon, 1969, et al. (författare) Semi-Analytical Model of the Rician K-Factor 2020 Ingår i: Radio Science. - 0048-6604 .- 1944-799X. ; 55:11 Tidskriftsartikel (refereegranskat)abstract The analysis of the performance of 5G wireless communication systems employing Massive MIMO at millimeter-wave frequencies is of great practical relevance. Of special relevance are the signal fluctuations. In the present paper, we introduce a semi-analytical model for a generic scattering environment by using randomly distributed resonant scatterers to investigate the impact of the size of the scattering environment, the scatterer density, and the number of scatterers on the signal variability in terms of the Rician K-factor as a function of frequency. We further present an investigation of the impact of scattering on the frequency dependence of the signal fading statistics in the 500 MHz–100 GHz band. The simplified model is also verified against full-wave simulation using the Method of Moments (MoM).

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