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1.	Alayon Glazunov, Andres, 1969-, et al. (författare) On Some Optimal MIMO Antenna Coefficients in Multipath Channels 2011 Ingår i: Progress in Electromagnetics Research B. - 1937-6472. ; 35, s. 87-109 Tidskriftsartikel (refereegranskat)abstract This paper derives some optimum transmit and receive antenna coefficients in wireless multipath channels based on the spherical vector wave multimode expansion of the multiple-input multiple-output (MIMO) channel matrix. The derived antenna coefficients satisfy the following specific optimization criteria: (i) maximum MIMO mean effective link gain (link MEG) based on the multimode channel realizations or (ii) maximum MIMO link MEG based on the multimode correlation matrix or (iii) correlation minimization by diagonalization of the MIMO full-correlation matrix. It is shown that the proposed approach leads to matrix equations belonging to the nearest Kronecker product (NKP) problem family, which in general have no trivial solution. However, we show that exact solutions are provided to the posed NKP problems under the assumption of the Kronecker model for the MIMO full-correlation matrix. The results are illustrated by numerical examples. The proposed approach is a complement to existing antenna pattern analysis methods.
2.	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. 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.
3.	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.
4.	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.
5.	Bagheri, Alireza, et al. (författare) A 16 × 16 45° Slant-Polarized Gapwaveguide Phased Array With 65-dBm EIRP at 28 GHz 2023 Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 71:2, s. 1319-1329 Tidskriftsartikel (refereegranskat)abstract A high equivalent isotropic radiated power (EIRP) active phased array antenna is proposed for fifth-generation (5G) communication systems at 28 GHz. The numerical design, measurements of a fabricated prototype, and performance analysis are presented. The antenna design is based on the gapwaveguide technology and consists of $16 \times 16$ single 45° slant-polarized elements. The proposed design uses a low complexity printed circuit board (PCB) structure with only six layers, i.e., a half of the existing wideband solutions. The array antenna incorporates up/downconverter integrated circuits (UDCs) and $1 \times 4$ transceiver beamformer integrated circuits (BFICs). Moreover, a compact and highly efficient transition at the end of each channel of the BFICs has been designed to interconnect the antenna elements with the PCB. The antenna's front-end loss, which includes the feed line, mismatch, and ohmic losses, is only 1.3 dB. The array covers the scanning range of ±60° in the azimuth plane and ±10° in the elevation plane. The $S_{11} < -10$ dB frequency bandwidth is from 26.5 to 29.5 GHz. The maximum EIRP of the antenna is 65.5 dBm at saturation point. The presented design offers a compact, robust, and low-loss performance solution meeting the high transmission power requirements of 5G applications.
6.	Bagheri, Alireza, et al. (författare) A ±45° Dual-Polarized Antenna for 5G mmWave Applications Based on Gap Waveguide Technology 2019 Ingår i: 2019 International Symposium on Antennas and Propagation, ISAP 2019 - Proceedings. Konferensbidrag (refereegranskat)abstract A ±45° dual-polarized antenna is designed based on the gap waveguide technology which offers a low loss and easy-to-manufacture solution at the mmWave frequencies. Dual-polarized antennas help to increase the capacity and coverage of a wireless system and also decrease the overall cost. Two parallel arrays of 8 slots each are employed to create the orthogonal polarizations. The antenna operates in the 24.25 - 27.25 GHz frequency band. The simulated average gain of each polarization is 14.5 dBi while achieving a cross-polarization isolation of at least 15 dB.
7.	Bagheri, Alireza, et al. (författare) Micro strip to Ridge Gap Waveguide Transition for 28 GHz Steerable Slot Array Antennas 2020 Ingår i: 2020 14TH EUROPEAN CONFERENCE ON ANTENNAS AND PROPAGATION (EUCAP 2020). - 2164-3342. - 9788831299008 Konferensbidrag (refereegranskat)abstract In this paper three types of contactless vertical transitions from microstrip to double ridge waveguide are presented. The designs are compact in size and robust, with improved isolation by employing a pin structure, making them ideal for SG mmWave phased arrays. All transitions cover the 26.5 - 29.5 GHz band, their dimensions are less than half a wavelength in pitch and have insertion losses less than 0.6 dB. The three designs apply different matching strategies and offer a trade-off between bandwidth and PCB areas. Finally, the behavior within an array configuration is analyzed.
8.	Bagheri, Alireza, et al. (författare) MmWave array antenna based on gap waveguide technology for 5G applications 2019 Ingår i: Proceedings of the 2019 21st International Conference on Electromagnetics in Advanced Applications, ICEAA 2019. ; , s. 492-494 Konferensbidrag (refereegranskat)abstract The gap waveguide technology has been shown to provide low loss and easy-to-manufacture antenna solutions in the mmWave frequencies. A gap waveguide array antenna with scanning ability within ±45° designed with focus on 5G applications is presented here. The computed active reflection coefficient of the array is less than -10 dB for all scan angles and the broadside gain is 23 dBi. The proposed antenna can be integrated with active components to increase EIRP and coverage range.
9.	Bagheri, Alireza, et al. (författare) TX Beamforming EVM Performance of a 65 dBm-EIRP Slant-Polarized Gapwaveguide Phased Array at 28 GHz 2023 Ingår i: 17th European Conference on Antennas and Propagation, EuCAP 2023. Konferensbidrag (refereegranskat)abstract The transmit error vector magnitude (EVM) performance measurements of a slant-polarized 28 GHz gapwaveguide-based phased array is analyzed in this paper. The performance is studied by using a large range of signals, with varied powers, symbol rates, and quadrature amplitude modulation (QAM) orders. The measurements have been conducted for four different scanning angles. A non-standardized over-the-air (OTA) link between the phased array and the receiver in a laboratory environment is used. The results show that the phased array antenna supports a 31 dB effective isotropic radiated power (EIRP) dynamic range at a maximum 2% EVM when transmitting a 64QAM modulated signal with 250 MS/s symbol rate at all scanning directions.
10.	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.
11.	Bärring, Maja, 1988, et al. (författare) Factory Radio Design of a 5G Network in Offline Mode 2021 Ingår i: IEEE Access. - 2169-3536 .- 2169-3536. ; 9, s. 23095-23109 Tidskriftsartikel (refereegranskat)abstract The manufacturing industry is connecting people and equipment with new digital technologies, enabling a more continuous stream of data to represent processes. With more things connected, the interest in a connectivity solution that can support communication with high reliability and availability will increase. The fifth generation of telecommunication, i.e., 5G has promising features to deliver this, but the factory environment introduces new challenges to ensure reliable radio coverage. This will require efficient ways to plan the Factory Radio Design prior to installation. 3D laser scanning is used at an ever-increasing rate for capturing the spatial geometry in a virtual representation to perform layout planning of factories. This paper presents how to combine 3D laser scanning and physical optics (PO) for planning the Factory Radio Design of a cellular Long-Term Evolution (LTE) network (5G) in a virtual environment. 3D laser scanning is applied to obtain the spatial data of the factory and the virtual representation serves as the environment where PO computation techniques can be performed. The simulation result is validated in this paper by comparison to measurements of the installed network and empirical propagation models. The results of the study show promising opportunities to simulate the radio coverage in a virtual representation of a factory environment.
12.	Carlsson, Jan, 1962, et al. (författare) Reverberation chamber for OTA measurements: The history of a dream! 2017 Ingår i: 2017 11th European Conference on Antennas and Propagation, EUCAP 2017. - 9788890701870 ; , s. 237-241 Konferensbidrag (refereegranskat)abstract In the late 1990's Professor Per-Simon Kildal got the idea that reverberation chambers could be used for characterizing small antennas and mobile devices. Many thought the idea was crazy but he was persistent and worked hard to realize his dream to build a small chamber that could be used by the wireless industry. This paper gives a short history of the research at Chalmers and the creation of the company Bluetest that both were instrumental for realizing the dream.
13.	Dang, Wen, et al. (författare) Ultra-wideband, Wide Scanning Phased Array for SATCOM Ground Station 2022 Ingår i: 2022 International Symposium on Antennas and Propagation, ISAP 2022. ; , s. 57-58 Konferensbidrag (refereegranskat)abstract We present the unit cell of a linearly polarised, ultra-wideband (UWB), wide scanning array antenna based on the tightly-coupled dipole antenna (TCDA) concept for cost-effective Ku/Ka-band SATCOM ground station applications. The TCDA unit cell is fed by a coaxial structure and several vias are used to broaden the bandwidth. In addition, a superstrate, functioning as a wide angle impedance matching (WAIM) layer, is employed to achieve together with an E-wall to reduce surface-waves. The simulated results show that the proposed TCDA provide a large bandwidth from 10.6-27.8 GHz at VSWR ≤ 2.0 at broadside radiation. Scanning angles up to 65° and 75° at the E- and H-plane, respectively, are maintained over the desired frequency of 12-1S GHz at VSWR ≤ 2.5.
14.	Glazunov, Andres Alayon, 1969, et al. (författare) A spherical probability distribution model of the user-induced mobile phone orientation 2018 Ingår i: IEEE Access. - 2169-3536 .- 2169-3536. ; 6, s. 37185-37194 Tidskriftsartikel (refereegranskat)abstract This paper presents a statistical modeling approach of the real-life user-induced randomness due to mobile phone orientations for different phone usage types. As well-known, the radiated performance of a wireless device depends on its orientation and position relative to the user. Therefore, realistic handset usage models will lead to more accurate over-the-air characterization measurements for antennas and wireless devices in general. We introduce a phone usage classification based on the network access modes, e.g., voice (circuit switched) or non-voice (packet switched) services, and the use of accessories, such as wired or Bluetooth handsets, or a speaker-phone during the network access session. The random phone orientation is then modeled by the spherical von Mises-Fisher distribution for each of the identified phone usage types. A finite mixture model based on the individual probability distribution functions and heuristic weights is also presented. The models are based on data collected from built-in accelerometer measurements. Our approach offers a straightforward modeling of the user-induced random orientation for different phone usage types. The models can be used in the design of better handsets and antenna systems as well as for the design and optimization of wireless networks.
15.	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.
16.	Glazunov, Andres Alayon, 1969, et al. (författare) Devising a Horizontal Chamber Array for Automotive OTA Tests in Random Line-Of-Sight 2016 Ingår i: International Symposium on Antennas and Propagation (ISAP), Hobart, Australia, 9-12 November, 2015. ; , s. Art. no. 7447285- Konferensbidrag (refereegranskat)abstract In this paper we propose an approach to design a horizontal array antenna to reduce the uncertainty of reference measurements in Random Line-Of-Sight Over-The-Air testing in anechoic chambers. The main focus is on wireless communications testing to and from automotive vehicles. The proposed procedure allows to determine the size, the spacing and the number of elements of a horizontal array antenna resulting in an absolute error less than 1 dB. The analysis is based on presenting the output of the ideal digital threshold receiver model of the device under test as a Probability of Detection curve.
17.	Glazunov, Andres Alayon, 1969 (författare) Downlink Massive MIMO performance of a vertically polarized uniform linear array in Random Line-Of-Sight 2016 Ingår i: 10th European Conference on Antennas and Propagation, EuCAP 2016; Davos; Switzerland; 10 April 2016 through 15 April 2016. - 2164-3342. - 9788890701863 ; , s. Art. no. 7481947- Konferensbidrag (refereegranskat)abstract In the present paper we study the downlink performance of a Massive Multi-User Multiple-Input Multiple-Output narrowband system in Random Line-Of-Sight scenarios. We evaluate the ergodic sum rate for the Zero-Forcing and the Matched-Filtering precoders. We consider a single-cell system comprising a base station with 100 Huygens source antenna elements and 10 users each equipped with a single dipole antenna. No coupling effects between the array elements have been assumed. We show that in a Random Line-Of-Sight environment, the MF precoding performance is better than the ZF over a wider range of average per-user signal-to-noise ratio as compared to the i.i.d. case.
18.	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.
19.	Glazunov, Andres Alayon, 1969 (författare) Far-field Reference Distance Criteria for Compact OTA Testing Ranges 2019 Ingår i: 2019 13TH EUROPEAN CONFERENCE ON ANTENNAS AND PROPAGATION (EUCAP). - 2164-3342. - 9788890701887 Konferensbidrag (refereegranskat)abstract Analyzed are three criteria for the computation of a reference distance marking the start of the far-field region in antenna measurements. The analysis is based on a correction factor for the Friis formula at boresight in the Fresnel zone. Closed form equations are obtained as a function of frequency, the gains of the transmit and receive antennas and a user-defined accuracy factor. Based on the above a far-field reference distance similar to the Fraunhofer distance criterium is defined. The presented results will be essential to design cost-efficient characterization of wireless devices of any size with user-defined accuracy.
20.	Glazunov, Andres Alayon, 1969, et al. (författare) Impact of Azimuthal Antenna Pattern Sampling and Variation on Throughput Measurements 2019 Ingår i: 2019 IEEE Conference on Antenna Measurements & Applications (CAMA). - 9781728123967 ; , s. 167-170 Konferensbidrag (refereegranskat)abstract Presented is a numerical study of the impact of the antenna pattern sampling resolution on the accuracy of Over-The-Air (OTA) throughput measurements. More specifically, a Line-Of-Sight (Random-LOS) testing scenario is addressed. The communication throughput is evaluated as the Probability of Detection (PoD) of a single bitstream based on the ideal digital threshold receiver model. The maximum deviation of throughput efficiency is computed as a function of the azimuthal sampling resolution for various generic antenna gain patterns. The coefficient of variation of the antenna gain pattern is introduced to evaluate the impact of the azimuthal sampling. The presented approach can be used to define the sampling resolution of the throughput performance of a device under test in Random-LOS OTA.
21.	Glazunov, Andres Alayon, 1969 (författare) Impact of deficient array antenna elements on downlink massive MIMO performance in RIMP and random-lOs channels 2018 Ingår i: IET Conference Publications. - : Institution of Engineering and Technology. ; 2018:CP741 Konferensbidrag (refereegranskat)abstract The Over-the-Air (OTA) characterization of large antenna systems need to be time- and cost-efficient. Among others, two potential candidates are OTA measurement environments emulating the Rich Isotropic MultiPath (RIMP) and the Random Line-Of-Sight (Random-LOS) channels. In the present paper we study the capacity loss of downlink massive multi-user multiple-input multiple-output (Massive MIMO) narrowband systems in these channels due to deficient antenna elements. We evaluate the downlink ergodic sum rate for the Zero-Forcing (ZF) and the Matched-Filtering (MF) precoders in these channels. We consider a single-cell system comprising a base station with 50 equidistant isotropic source antenna elements placed λ/2 apart and 5 users each equipped with a single isotropic antenna. No coupling effects between the array elements have been assumed. In the present study we show that both the RIMP and the Random-LOS can be used to identify deficient performance of Massive MIMO arrays.
22.	Glazunov, Andres Alayon, 1969 (författare) Impact of Test Zone Polarization-Imbalance on MIMO efficiency in a Random-LOS OTA Setup 2022 Ingår i: 2022 International Symposium on Antennas and Propagation, ISAP 2022. ; , s. 521-522 Konferensbidrag (refereegranskat)abstract Presented is an evaluation of the impact of the power imbalance between the vertical and horizontal polarization in the test zone of a random line-of-sight over-the-air characterization system on multiple-input multiple-output efficiency.
23.	Glazunov, Andres Alayon, 1969, et al. (författare) Impact of the Spatial User Distribution on the Coverage Antenna Pattern of Maximum Ratio Combining in Random Line-Of-Sight 2015 Ingår i: 9th European Conference on Antennas and Propagation, EuCAP 2015, Lisbon, Portugal, 13-17 May 2015. - 9788890701856 Konferensbidrag (refereegranskat)abstract In this paper we investigate the impact of the spatial user distribution on the Maximum Ratio Combining (MRC) of the output signals from an ideal 4-port antenna. The antenna consists of four elementary Huygens sources operating in Random Line-Of-Sight (RLOS). The antenna is assumed to be wall-mounted. Two specific scenarios for the user distribution are considered, i.e., the 3D hemisphere and a rectangular prism emulating a corridor or a rectangular room. We present simulation results in terms of the cumulative distribution functions corresponding to the resulting polarisation and pattern diversity of 1-bitstream and the corresponding coverage radiation pattern of the 4-port antenna system. We also show that there is an antenna arrangement that maximizes the diversity gain that will be different for different spatial distributions of users.
24.	Glazunov, Andres Alayon, 1969, et al. (författare) Impact of User Spread on the Input Power Spread in DL Massive MIMO in Random LOS Channels 2020 Ingår i: 2020 USNC-URSI Radio Science Meeting (Joint with AP-S Symposium), USNC/URSI 2020 - Proceedings. ; , s. 67-68 Konferensbidrag (refereegranskat)abstract Presented are the spread of the amplifier output power and the sum rate capacity loss of a narrowband massive MIMO antenna system in a Random-LOS channel due to cell-sector narrowing. Coupling effects between the array elements have been neglected. A large power spread of the output power of the amplifiers is observed when users are spread over narrow sectors and ZF-precoding is used. The capacity is considerably reduced for both MF- and ZF-precoding, especially for the latter.
25.	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.
26.	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 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.
27.	Glazunov, Andres Alayon, 1969, et al. (författare) Reverberating Dreams - the Story of an OTA Chamber 2017 Ingår i: 2017 IEEE INTERNATIONAL SYMPOSIUM ON ANTENNAS AND PROPAGATION & USNC/URSI NATIONAL RADIO SCIENCE MEETING. - 1522-3965. - 9781538632840 ; , s. 239-240 Konferensbidrag (refereegranskat)abstract By the late 90's Prof. Per-Simon Kildal came to the insight that reverberation chambers could be useful tools for characterizing small antennas and wireless devices in multipath channels. This was a revolutionizing idea that was not so well received at first. However, with perseverance, he worked through the challenges to see his dream become a reality. This paper is to recognize Prof. Kildal's contributions carried out at Chalmers, the spin-off company Bluetest, but also the contributions of many other people that have been key to materializing his dream.
28.	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).
29.	Glazunov, Andres Alayon, 1969, et al. (författare) Simulating the MIMO Efficiency of Antennas 2017 Ingår i: 2017 INTERNATIONAL SYMPOSIUM ON ANTENNAS AND PROPAGATION (ISAP 2017). - 9781538604656 ; 2017-January Konferensbidrag (refereegranskat)abstract Presented is a mathematical model to compute the multiple-input multiple-output efficiency of a multiport antenna in the single-user case. The evaluation comprises the performance of a zero-forcing receiver in two limiting propagation scenarios, i.e., the random line-of-sight and the rich isotropic multipath channels.
30.	Glazunov, Andres Alayon, 1969, et al. (författare) Simulations of a planar array arrangement for automotive Random-LOS OTA testing 2016 Ingår i: 2016 10th European Conference on Antennas and Propagation, EuCAP 2016. - 9788890701863 ; , s. 7481285- Konferensbidrag (refereegranskat)abstract We present simulations of near-field plane wave synthesis by a planar array. The focus is on minimization of reference signal errors within the test zone for Random Line-Of-Sight Over-The-Air characterization of wireless devices on cars. The analysis considers the output of the ideal digital threshold receiver model of the device under test as a Probability of Detection curve. The dimensions, the interelement spacings and the number of elements in a planar array comprising Huygens sources are investigated to produce an absolute error less than 0.5 dB.
31.	Glazunov, Andres Alayon, 1969 (författare) Test Zone Characterization in an Automotive Random-LOS OTA Test Setup 2017 Ingår i: PROCEEDINGS OF THE 2017 IEEE-APS TOPICAL CONFERENCE ON ANTENNAS AND PROPAGATION IN WIRELESS COMMUNICATIONS (APWC). - 9781509044542 ; , s. 170-173 Konferensbidrag (refereegranskat)abstract Presented is a method to produce a 2D reference test zone for over-the-air measurements in a random line-of-sight environment for vehicular applications. The ideal threshold receiver model is used to design the chamber array at 3 GHz for LTE/LTE-A systems. The analysis focuses on the fluctuations of the reference power measurements at a user-defined probability of detection level of bitstreams. Numerical results of the test zone characterization are presented assuming an ideal anechoic chamber is used.
32.	Glazunov, Andres Alayon, 1969, et al. (författare) Zero-forcing MIMO efficiency in random line-of-sight 2016 Ingår i: 2016 IEEE Antennas and Propagation Society International Symposium, APSURSI 2016, Fajardo, Puerto Rico, 26 June - 1 July 2016. - 1522-3965. - 9781509028863 ; , s. 331-332 Konferensbidrag (refereegranskat)abstract We derive the Multiple-Input Multiple-Output (MIMO) efficiency of the Zero-Forcing (ZF) receiver algorithm in Random Line-Of-Sight (Random-LOS). We make use of the Probability-of-Detection (PoD) curves based on the ideal digital threshold receiver model in the derivations. We show that the MIMO efficiency in this case, is mainly determined by two factors: the smallest channel gain of the two available bit streams and the non-orthogonality coefficient. This must be considered when designing antenna systems for efficient communication at higher frequencies since Random-LOS propagation will be dominating.
33.	Hussain, Ahmed, 1985, et al. (författare) Antenna Measurements in Reverberation Chamber Using USRP 2016 Ingår i: IEEE Transactions on Antennas and Propagation. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-926X .- 1558-2221. ; 64:3, s. 1152-1157 Tidskriftsartikel (refereegranskat)abstract This paper shows that a universal software radio peripheral (USRP) can be used to measure the complete passive over-the-air (OTA) performance of multipart antennas for multiple-input multiple output (MIMO) systems. The passive MIMO OTA measurements are performed in a reverberation chamber using the USRP as a measurement instrument. The total embedded radiation efficiencies, the correlation, and the resulting diversity gain are extracted from transmission measurements only. These are in good agreement with S-parameter measurements (both transmission and reflection) obtained with a vector network analyzer (VNA). The proposed measurement approach involving USRPs provide an economical alternative to these type of measurements as compared to high-end equipment.
34.	Hussain, Ahmed, 1985, et al. (författare) Interpreting the Total Isotropic Sensitivity and Diversity Gain of LTE-enabled wireless devices from Over The Air Throughput Measurements in Reverberation Chambers 2015 Ingår i: IEEE Access. - 2169-3536 .- 2169-3536. ; 3, s. 131-145 Tidskriftsartikel (refereegranskat)abstract The characterization of the performance of wireless devices is the key to developing new RF products conforming to the latest communications protocols. Traditionally, communication performance tests have focused on the RF performance of the tested devices, e.g., smart phones, pads, laptops, etc. More specifically, the focus has shifted from conducted (i.e.,cabled) measurements to more realistic Over-The-Air (OTA)characterization of the RF performance of these devices in transmit or receive mode. For example, the receiver performance of 2G and 3G wireless devices can be measured in terms of the total isotropic sensitivity (TIS) that depends on the antenna and the receiver parts of a wireless device. These measurements can be performed in a reverberation chamber setup. However, standard TIS measurements can be time consuming and do not reflect the actual performance gains of Multiple-Input Multiple-Output (MIMO) antenna systems operating over OrthogonalFrequency Division Multiplexing (OFDM) channels, such asthose encountered in 4G Long Term Evolution (LTE) systems. Therefore, in order to meet both time and cost efficiency requirements, we propose here a new method to determine the TIS, as well as the diversity performance, of an LTE device based on throughput measurements. The proposed method shows that the TIS of an LTE device is characterized much faster directly from OTA throughput measurements than from standard TIS measurements and with excellent accuracy.
35.	Iupikov, Oleg, 1983, et al. (författare) Hybrid OTA Chamber for Multi-Directional Testing of Wireless Devices: Plane Wave Spectrum Generator Design and Experimental Demonstration 2022 Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 70:11, s. 10974-10987 Tidskriftsartikel (refereegranskat)abstract This paper investigates practical implementation aspects of a novel hybrid chamber concept that has been recently introduced for over-the-air testing of wireless devices. The chamber allows to synthesize a spectrum of plane waves (PWs) incident on a device under test from a wide range of angles-of-arrival (AoAs) through exploiting multiple field scattering inside the overmoded waveguide chamber. An optimal design approach for the plane wave spectrum generator (PWSG) array inside the chamber is presented considering: (i) array antenna impedance matching for the desired test zone (TZ) quality and AoAs range; (ii) an operational frequency bandwidth of the test environment and an instantaneous signal bandwidth; and (iii) the impact of the PWSG excitation errors. A robust linearly constrained minimum variance (LCMV) beamformer is formulated to realize the desired test environment over a wide frequency band, while accounting for the varying number of the waveguide propagating modes as excited by the PWSG array. Numerical simulations and measurements with the first prototype of the hybrid chamber for FR1 frequency band (~3.5 GHz) are presented. This prototype includes a 7 × 7 bowtie antenna element PWSG array, a 1.00 × 1.25 × 1.75 m metal waveguide chamber, an off-line optimal array beamforming setup, and a planar scanner for the TZ characterization.
36.	Iupikov, Oleg, 1983, et al. (författare) Indoor Received Power Prediction Based on Physical Optics (PO): Simulations and Experimental Validation in Industrial Environment 2019 Ingår i: 13th European Conference on Antennas and Propagation, EuCAP 2019. Konferensbidrag (refereegranskat)abstract This study presents an approach based on Physical Optics computations to predict the receive signal power in an indoor environment. The application in focus pertains the development of highly reliable manufacturing industry processes where wireless communications plays a key role. Our proposed numerical method shows a good agreement with measurement data. It is therefore suggested that Electromagnetic modelling based on computationally efficient Physical Optics algorithms can be used as a complement, an alternative or even a replacement for empirical models requiring time consuming measurement campaigns.
37.	Iupikov, Oleg, 1983, et al. (författare) The Hybrid Chamber for OTA measurements: Plane Wave Spectrum Quality Vs. Dynamic Range Trade-off 2022 Ingår i: 2022 16th European Conference on Antennas and Propagation, EuCAP 2022. Konferensbidrag (refereegranskat)abstract In this paper, the trade-off between the quality of the plane wave spectrum synthesized in the test zone of the hybrid over-the-air (OTA) chamber and factors affecting the dynamic range of this measurement system is investigated. The hybrid chamber performance is compared to a plane wave generator (PWG) in free space. The performance evaluation is focused on the field radiated into the test zone (TZ) while maintaining its quality according to 3GPP specification. It is demonstrated that a good quality can be achieved for the synthesized plane wave spectrum.
38.	Kanters, Noud, et al. (författare) A Supervised Learning Framework for Joint Estimation of Angles-of-Arrival and Number of Sources 2022 Ingår i: IEEE Access. - 2169-3536 .- 2169-3536. ; 10, s. 112086-112099 Tidskriftsartikel (refereegranskat)abstract Machine learning is a promising technique for angle-of-arrival (AOA) estimation of waves impinging a sensor array. However, the majority of the methods proposed so far only consider a known, fixed number of impinging waves, i.e., a fixed number of sources (NOS). This paper proposes a machine-learning-based estimator designed for the case when the NOS is variable and hence unknown a priori. The proposed estimator comprises a framework of single-label classifiers. Each classifier predicts if waves are present within certain randomly selected segments of the array's field of view (FOV), resulting from discretising the FOV with a certain (FOV) resolution. The classifiers' predictions are combined into a probabilistic angle spectrum, whereupon the NOS and the AOAs are estimated jointly by applying a probability threshold whose optimal level is learned from data. The estimator's performance is assessed using a new performance metric: the joint AOA estimation success rate. Numerical simulations show that for low SNR (-10 dB), a low FOV resolution (2°) yields a higher success rate than a high resolution (1°), whereas the opposite applies for mid (0 dB) and high (10 dB) SNRs. In nearly all simulations, except one at low SNR and a high FOV resolution, the proposed estimator outperforms the MUSIC algorithm if the maximum allowed AOA estimation error is approximately equal to (or larger than) the FOV resolution.
39.	Kanters, Noud, et al. (författare) Channel Estimation Errors and Their Impact on Irregular Array Performance in Massive MIMO 2022 Ingår i: 2022 International Symposium on Antennas and Propagation, ISAP 2022. ; , s. 509-510 Konferensbidrag (refereegranskat)abstract This paper considers the impact of imperfect channel state information (CSI) on the array antenna layout design in massive multiple-input multiple-output applications. The analysis is based on channel estimation errors resulting from the least squares estimation algorithm in pure line-of-sight channels. We show that signal to interference-plus-noise ratio gains traditionally anticipated with irregular layouts, as compared to regular ones under the assumption of perfect CSI, vanish in case of CSI imperfections for the considered scenario.
40.	Kildal, Per-Simon, 1951, et al. (författare) Cost-effective measurement setups for testing wireless communication to vehicles in reverberation chambers and anechoic chambers 2014 Ingår i: 2014 IEEE Conference on Antenna Measurements and Applications, CAMA. - : Institute of Electrical and Electronics Engineers. Konferensbidrag (refereegranskat)abstract Autonomous (self-driving) cars will in a few years become a reality, driven by safety aspects. This will be made possible by reliable and secure wireless connections to the car via the wireless network, and directly from other vehicles in the close vicinity. Thereby OTA-testing becomes a big issue, both in multipath and Line-Of-Sight (LOS). The present paper proposes two compact and cost-effective test chambers that take account of the two limiting environments known as Rich Isotropic Multipath (RIMP) and Random-LOS. The randomness of the latter is associated with the unknown and arbitrarily distributed angle of arrival of the LOS in the horizontal plane, sometimes also having an unknown polarization, which thereby also become random.
41.	Kildal, Per-Simon, 1951, et al. (författare) Optimizing Small Wideband Antenna Performance for Both RIMP and Random-LOS 2015 Ingår i: 9th European Conference on Antennas and Propagation, EuCAP 2015, Lisbon, Portugal, 13-17 May 2015. - 9788890701856 Konferensbidrag (refereegranskat)abstract Rich Isotropic Multipath (RIMP) environment likereverberation chamber (RC) has proven to be useful forcharacterizing mobile LTE devices. The user statistics have larger effect in environments with stronger Line-Of-Sight (LOS), because the angle of arrival (AoA) and the polarization of the LOS contribution become randomized due to the user. Thus, we introduce the term Random-LOS. The present paper elaborates on characterization of an example antenna in both RIMP and random-LOS. We show how to characterize the micro BTS by the probability of detection (PoD) of one and more bitstreams in both RIMP and random-LOS, by considering the user randomly located and oriented within the angular coverage sector. We limit the treatment to a wall-mounted BTS antenna, and assume a desired hemi-spherical coverage.
42.	Kildal, Per-Simon, 1951, et al. (författare) OTA Testing of 3G-5G Devices with MIMO: From Anechoic Chambers to Reverberation Chambers and ... Back Again? 2017 Ingår i: IEEE Antennas and Propagation Society International Symposium. - 1522-3965. - 9781538632840 ; 2017-January, s. 1697-1698 Konferensbidrag (refereegranskat)abstract The present paper describes the paradigm shift in OTA testing that came with the arrival of the 4G wireless system. The testing was previously mainly done in anechoic Line-Of-Sight (LOS) environments, and now in 4G it is done in reverberation chambers, emulating Rich Isotropic MultiPath (RIMP). Now we are preparing for the 5G wireless system, which is expected to have mm-wave antennas with steerable lobes. This will require OTA testing in anechoic environments again, but with an emphasis on system measurements, i.e. data rate throughput for an arbitrary location and orientation of the user, referred to as Random-LOS.
43.	Kon, Ryosuke, et al. (författare) Wideband H-slot antenna fed by substrate integrated gap waveguide for mmWave arrays 2021 Ingår i: 2020 International Symposium on Antennas and Propagation, ISAP 2020. ; , s. 577-578 Konferensbidrag (refereegranskat)abstract This paper proposes a wideband slot antenna design based on the substrate integrated gap waveguide technology for millimetre wave applications. The proposed antenna is realized using the H-shaped slot (H-slot) to improve impedance bandwdith. Simulation results show that the proposed antenna has an impedance bandwidth at S11 ≤-15 dB from 24-29.5 GHz resulting in a 20.5% fractional bandwidth. Hence, the designed slot antenna can potentially be used as the radiating element of an array antenna for fixed-beam point-to-point applications.
44.	Krasov, Pavlo, 1981, et al. (författare) Characterization and Calibration of the Hybrid OTA Chamber Using a Field Scanner 2022 Ingår i: 2022 16th European Conference on Antennas and Propagation, EuCAP 2022. Konferensbidrag (refereegranskat)abstract This paper investigates the characterization and calibration procedure of the hybrid over-the-air (OTA) measurement chamber. We present a prototype of the hybrid chamber and analyze its capabilities to generate a plane wave spectrum in practice. A planar field scanner is used to acquire the embedded element fields of the chamber array for test zone (TZ) synthesis in post-processing. The repeatability of the field acquisition is evaluated. It is shown that the synthesized TZ meets the 3GPP specifications for TZ field variations for plane wave generators (PWG) in the presence of acquisition imperfections.
45.	Krasov, Pavlo, 1981, et al. (författare) Quiet Zone Quality of a Plane Wave Generator inside an Over-Moded Waveguide Chamber Emulating a Variable Angle of Incidence 2021 Ingår i: 15th European Conference on Antennas and Propagation, EuCAP 2021. Konferensbidrag (refereegranskat)abstract We investigate the use of a hybrid over-the-air (OTA) measurement chamber to emulate far-field testing conditions. The focus has been on the generation of a plane wave arriving at an arbitrary angle-of-arrival (AoA) to the device-under-test (DUT) without mechanical steering. The chamber consists of an oversized waveguide (WG) and a planar array antenna with adaptive beamforming. A modified linear constrained minimum variance (LCMV) beamforming algorithm is used to form a quiet zone (QZ) in the DUT region by using the reflections from the WG's metal walls. The LCMV beamformer formulation has been extended to achieve a volumetric QZ with the desired amplitude and phase uniformity. Numerical studies for the QZ size corresponding to an FR1 base station demonstrate promising results with the low levels of amplitude and phase variation. The AoA coverage of this chamber meets 3GPP specification requirements for OTA conformance testing of base stations with active antenna systems.
46.	Krasov, Pavlo, 1981, et al. (författare) Reconfiguration Capabilities of the Anechoic-Reverberation Hybrid Chamber for TRP Measurements of Active Antenna Systems 2023 Ingår i: 17th European Conference on Antennas and Propagation, EuCAP 2023. Konferensbidrag (refereegranskat)abstract A hybrid, reconfigurable anechoic-reverberation antenna measurement chamber was recently introduced with the vision to enable fast characterization of the active antenna radiated power and directive characteristics in a single measurement environment. The initial studies included its design and analysis in the plane wave spectrum generator scenario. In the present work, we investigate chamber reconfiguration capabilities for performing total radiated power (TRP) measurements. We show how different types of interchangeable hybrid chamber modules allow realizing several possible ways of measuring TRP. Trade-offs in terms of measurement time and implementation complexity are discussed. Finally, one of the methods, using a chamber array antenna module, is selected and demonstrated in simulations. Our initial results indicate TRP measurement error within ±0.5 dB.
47.	Lehne, Per H., et al. (författare) Analyzing smart phones' 3D accelerometer measurements to identify typical usage positions in voice mode 2016 Ingår i: 10th European Conference on Antennas and Propagation, EuCAP 2016; Davos; Switzerland; 10 April 2016 through 15 April 2016. - 2164-3342. - 9788890701863 ; , s. Art. no. 7481895- Konferensbidrag (refereegranskat)abstract Smart phone sensors provide new possibilities to understand how devices are actually used and handled in real-life situations. Such information can possibly be used to design better handsets, but also to improve network performance. For example, the radiated performance of a wireless device depends on its orientation and position relative to the user. Hence, knowing realistic handset usage plays a major role in the Over-The-Air characterization of antennas and wireless devices in general. This paper presents an analysis of usage positions for voice service. A simplified statistical model based on data collected from devices acceleration sensors is presented. The analysis shows interesting results from which we can identify some typical ways the user is handling the phone when in a voice conversation. Our analysis shows clear differences of the orientation of the handset when used with a handsfree set and when not.
48.	Lehne, Per Hjalmar, et al. (författare) Finding the distribution of users in a cell from smart phone based measurements 2016 Ingår i: Proceedings of the International Symposium on Wireless Communication Systems. - 2154-0217 .- 2154-0225. - 9781509020614 ; , s. 538-542 Konferensbidrag (refereegranskat)abstract Mobile users are assumed to be positioned within the cell or sector boundaries of the serving cell in the network. Measurements of location done by the smart phones combined with the network layout show differently. There is a significant amount of users which are actually outside the nominal sector boundaries. Knowledge about the statistical location distribution of users inside or outside the serving cell intended coverage may prove valuable in finding more optimal resource management methods. Another application is the development of over-the-air characterization of base station antennas. Distance and directional statistics are shown for samples of relative positions within the cell sectors of a real network using smart phone based measurements. Samples for LTE in 800 and 1800 MHz non-voice usage and 3G at 2100 MHz voice usage is included. The distance distributions show clearly that the usage density rapidly decrease with the distance, and there is a clear confirmation that lower frequencies have longer range, also in terms of usage density. Mean usage distance for 800 MHz is 1.62 km, while for 2100 MHz it is only 580 m. It also shows that 90% of the usage is within 3.47 and 1.35 km for the two cases, respectively. The directional distributions relative to the sector centre direction shows that 80% of the users are within 153 degrees for lowest frequency, and 109 degrees for the highest.
49.	Lehne, Per Hjalmar, et al. (författare) Measuring user-induced-randomness to evaluate smart phone performance in real envi-ronments 2015 Ingår i: 9th European Conference on Antennas and Propagation, EuCAP 2015, Lisbon, Portugal, 13-17 May 2015. - 9788890701856 Konferensbidrag (refereegranskat)abstract The radiated performance of a wireless device depends on its orientation and position relative to the user. In addition, the antenna performance is different on different devices and it depends on the device model. Hence, to understand the impact of the users behaviour on the device antenna and the resulting network performance an investigation of the device usage and signal quality is of high importance. This paper presents a first analysis of the orientation usage of wireless devices based on data gathered from 5 smart phones over a period of more than two months. The data was obtained from the built-in sensors in the phone, and includes angles of orientation, information about signal quality and the connected network Some interesting trends regarding typical orientations of the phone are presented for both voice and data services. We believe that data of this type has the potential to be used for optimizing the device and the network performance, e.g., when the data is correlated with the experienced channel quality.
50.	Maaskant, Rob, 1978, et al. (författare) A New Hybrid Chamber for Generating a Spectrum of Oblique Incident Plane Waves at the DUT 2021 Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 69:10, s. 6806-6815 Tidskriftsartikel (refereegranskat)abstract A novel type of hybrid measurement facility comprising a chamber antenna array (CAA) inside an overmoded waveguide is proposed and analyzed numerically. The reflecting walls of the metal rectangular waveguide (WG) are used in conjunction with a CAA to synthesize obliquely incident plane wave (PW) fields at the device under test (DUT). This enables increased flexibility in emulating almost any PW multipath testing conditions in the WG chamber without the high cost and complexity of classical anechoic measurement systems employing relatively large phase-steered plane wave generators. A modeling framework is proposed that has been used to devise first-order design rules (e.g. the number of independent propagating modes, dimensions of the WG, CAA, and DUT). Afterwards, an optimally beamformed CAA example is presented to numerically validate the quality of the on- and off-axis plane wave fields in the test zone. This study shows design trade-offs between the amplitude ripple in the DUT region, the total power focused in this region, the DUT size and the angle of incidence.

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