Showing papers on "Active antenna published in 2021"

Deep Learning Optimized Sparse Antenna Activation for Reconfigurable Intelligent Surface Assisted Communication

Abstract: Reconfigurable intelligent surface (RIS) is a revolutionary technology for achieving high rate and large coverage in future wireless networks by smartly reflecting the signals with adjustable phase shifts. To design the reflection beamforming, accurate individual channel state information is required at the RIS, which is a challenge task due to the lack of signal processing ability in passive mode. In this paper, we add signal processing units for a few antennas at the RIS to partially acquire the channels and extrapolate them to the full channels, in which the active antenna selection is a key point but has not been addressed yet. We construct an active antenna selection network that utilizes the probabilistic sampling theory to select the optimal locations of these active antennas. With this active antenna selection network, we further design two deep learning-based schemes, i.e., the channel extrapolation scheme and the beam searching scheme. The former utilizes the selection network and a convolutional neural network to extrapolate the full channels from the partial channels, while the latter adopts a fully-connected neural network to achieve the direct mapping from the partial channels to the optimal beamforming vector with maximal transmission rate. Simulation results show that the proposed optimal antenna selection outperforms the trivial uniform antenna selection, and the performance of beam searching is more stable than that of channel extrapolation with fewer active antennas.

Single-RF MIMO: From Spatial Modulation to Metasurface-Based Modulation

Abstract: In multiple-input multiple-output (MIMO) systems, multiple radio frequency (RF) chains are usually required to simultaneously transmit multiple data streams. As a special MIMO technology, spatial modulation (SM) activates one transmit antenna by requiring one RF chain and exploits the index of the active antenna for information transfer at each time slot. Recently, reconfigurable metasurfaces have emerged as a promising technology that is able to reconfigure the wireless propagation environment by altering the amplitude and/or phase of the incident signal. In this article, we aim for the implementation of single-RF MIMO by shifting the focus from SM to metasurface-based modulation. Specifically, the principles of SM and metasurfaces are first presented. After reviewing the evolution of SM, we elaborate on the idea of metasurface-aided single-RF MIMO and discuss some implementations for it in line with notable variants of SM. A comparison between antenna-based and meta-surface-based modulation is made to highlight the advantages of using metasurfaces. We finally investigate the research challenges and opportunities in the context of metasurface-based modulation.

Dual Band and Dual Diversity Four-Element MIMO Dipole for 5G Handsets.

Abstract: The increasing popularity of using wireless devices to handle routine tasks has increased the demand for incorporating multiple-input-multiple-output (MIMO) technology to utilize limited bandwidth efficiently. The presence of comparatively large space at the base station (BS) makes it straightforward to exploit the MIMO technology’s useful properties. From a mobile handset point of view, and limited space at the mobile handset, complex procedures are required to increase the number of active antenna elements. In this paper, to address such type of issues, a four-element MIMO dual band, dual diversity, dipole antenna has been proposed for 5G-enabled handsets. The proposed antenna design relies on space diversity as well as pattern diversity to provide an acceptable MIMO performance. The proposed dipole antenna simultaneously operates at 3.6 and 4.7 sub-6 GHz bands. The usefulness of the proposed 4×4 MIMO dipole antenna has been verified by comparing the simulated and measured results using a fabricated version of the proposed antenna. A specific absorption rate (SAR) analysis has been carried out using CST Voxel (a heterogeneous biological human head) model, which shows maximum SAR value for 10 g of head tissue is well below the permitted value of 2.0 W/kg. The total efficiency of each antenna element in this structure is −2.88, −3.12, −1.92 and −2.45 dB at 3.6 GHz, while at 4.7 GHz are −1.61, −2.19, −1.72 and −1.18 dB respectively. The isolation, envelope correlation coefficient (ECC) between the adjacent ports and the loss in capacity is below the standard margin, making the structure appropriate for MIMO applications. The effect of handgrip and the housing box on the total antenna efficiency is analyzed, and only 5% variation is observed, which results from careful placement of antenna elements.

On Half-Power Beamwidth of Intelligent Reflecting Surface

Abstract: Half-power beamwidth (HPBW) is a key parameter to measure the performance of antenna array and the newly proposed intelligent reflecting surface (IRS) systems. In this letter, we first establish a system model for IRS in uniform linear array (ULA) and uniform rectangular array (URA) configurations, then the IRS HPBW in both cases are derived under the far-field condition without considering channel path-loss and fading. We find that in ULA and URA configurations, IRS HPBW is equal to antenna array’s HPBW at the same reflect/transmit angle with maximal ratio combining applied, while IRS HPBW is always greater than or equal to antenna array’s HPBW when all weights are equal. Besides, under certain incident angles, there will be abrupt changes in HPBW and the analytical expressions of the boundary values in both ULA and URA cases are provided. Unlike the traditional active antenna array, our conclusion shows that the IRS HPBW will change with the incident angles. Simulation results verify the correctness of our derivations.

Investigation of power amplifier performance under load mismatch conditions

Abstract: The time-varying loading conditions that power amplifiers (PAs) experience in active antenna systems degrade their overall performance. Consequently, the design of linear and highly-efficient PAs under mismatch is more important than ever. In this paper, different common and promising PA architectures, i.e. class-B, balanced, Doherty (DPA) and load-modulated-power-amplifier (LMBA), are analyzed under mismatch. Their sensitivity in terms of linearity, efficiency and output power is compared under a LTE signal excitation. Average drain efficiency (DE), average output power, normalized-mean-square-error (NMSE) as well as maximum output power variations are presented for each architecture as function of the voltage-standing-waveratio (VSWR). Thereby, the most suitable PA architecture to be integrated in active antenna systems may be identified.

A Programmable-Metasurface-Based TDMA Fast Beam Switching Communication System at 28 GHz

Abstract: A programmable metasurface (PM) is a promising active antenna array approach for beamforming purposes. In comparison with a phased array, our interested PM achieves beamforming by electronically control the states of Pin diodes instead of phase shifters, which highly reduces the system price and power consumption. In this letter, a novel wireless communication system with an ultrafast beam steering ability using a PM at 28 GHz in a time-division multiple access (TDMA) scenario is constructed. Realization of the entire system dealing with technical specifications is introduced in detail. System performances with different beam switching times, modulation schemes, and frame structures are analyzed. As a conclusion, we prove that a PM system is a possible candidate for fast beam switching with low cost and complexity.

Performance Analysis of RIS-SSK in the Presence of Hardware Impairments

Abstract: Reconfigurable Intelligent Surface-based Space Shift Keying (RIS-SSK) was recently proposed as a promising transmission technique. In order to design strategic radio environments, this system takes advantage of RIS-based communication and adjusts the propagation channels. Furthermore, using SSK as a special case of the Spatial Modulation (SM) reduces the detection complexity by using only the index of the active antenna to transmit the data. However, when considering an effective RIS-SSK system, the transmit antenna is modeled by spatial constellation points with different weights. This requires the knowledge of Channel State Information (CSI), including the index of the activated antenna at each transmission which is impractical. In contrast, blind RIS-SSK does not require this information, decreasing its complexity and increasing its practicality. In this paper, a blind RIS-SSK system without phase-adjusting is studied in the presence of hardware impairments and compared to the standard SSK. Additionally, analytically error probability expressions based on the Maximum Likelihood (ML) detector are developed and proven with simulations. The results illustrate the negative effects of modeling the hardware impairments for robust RIS-SSK system implementation.

Co-Design and Validation Approach for Beam-Steerable Phased Arrays of Active Antenna Elements With Integrated Power Amplifiers

Abstract: An approach for designing a beam-steering active phased array of antenna elements with integrated power amplifiers (PAs) is presented. It is based on an amplifying active integrated unit cell (AiUC) concept, where the AiUC comprises a radiating slot element, a GaN high-electron-mobility transistor (HEMT), its input matching, and dc biasing/feeding circuitry. The HEMT is embedded in the antenna element, being directly impedance-matched to HEMT’s drain output, i.e., without using any intermediate and potentially lossy impedance matching network. The proposed co-design approach involves a full-wave analysis of the AiUC passive part (naturally including elements mutual coupling effects) along with the subsequent full-system harmonic balance simulations. Furthermore, we extend the standard definition of the scan element pattern (SEP) to the active SEP (ASEP) that accounts for nonlinear effects of PAs on the AiUC performance. We show that the ASEP is, in general, power-dependent and has a different shape compared with the SEP. The proposed approach has been demonstrated for a $K$ -band AiUC design example. It was verified through an active waveguide simulator, which is equivalent to the 23.7° H-plane beam-steering case. Measurements are in good agreement with simulations, revealing AiUC 47% peak drain efficiency and 33 dBm maximum radiated power. The predicted scan range is ±60° and ±37° in the E- and H-planes, respectively.

A Compact, Bistatic Antenna System with Very High Interport Isolation for 2.4 GHz In-Band Full Duplex Applications

Abstract: This paper presents a compact, dual polarized bistatic (two closely spaced transmit and receive radiators) patch antenna with excellent interport isolation performance. The presented antenna system employs differential receive mode operation for the cancellation of self-interference (SI) to achieve very high interport isolation for 2.4 GHz in-band full duplex (IBFD) applications. The presented antenna is based on two closely spaced radiators and a simple 3 dB/180° coupler for differentially excited receive mode operation. The 3 dB/180° coupler performs as a passive self-interference cancellation (SIC) circuit for the presented antenna. The small form-factor structure is realized through via interconnections between the receiving patch and SIC circuit. The prototype of the presented antenna characterizes better than 105 dB peak interport isolation. Moreover, the recorded interport isolation is more than 90 dB and 95 dB within 60 MHz and 40 MHz bandwidths, respectively. The measured gain and cross-polarization levels reflect superior radiation performance for the validation model of the proposed antenna. The presented antenna offers DC interport isolation too, which is required for active antenna applications. The novelty of this work is a compact (small form-factor) antenna structure with very high peak interport isolation along with wider SIC bandwidth as compared to previously reported antennas for full duplex applications.

Inflatable Coplanar Patch Antenna Array for Spaceborne Applications

Abstract: This paper presents the design of an inflatable coplanar patch antenna array as to increase the Technology readiness level (TRL) to 3 for application into future space-based radio astronomy antennas. The objective of this antenna is to communicate at 2.4 GHz with Earth when placed on a rocket. The advantage of using an inflatable antenna at its final destination in space is the ability to pack it in a small volume and unpack it in space. Earlier inflatable antennas have been designed as reflector antennas, thereby using the inflatable antenna surface as a passive reflective surface using metallized film. Previous research related to active inflatable antennas has focussed on the feasibility of using active antenna elements on an inflatable antenna for an ultra low frequency radio astronomy application. In this work, two designs are made on thin film and their electrical performance and structure is tested. These designs consist of a 2 by 4 patch antenna array, which are fed via coplanar waveguide connected to a micro coaxial connectors which have the advantage on being small and lightweight and lockable as to increase the retention force. The second design also contains a feeding network including a CPW Wilkinson divider and T-Junction. These prints were made from gold with a metal thickness of 150 nm on 25 µm thick BoPET film. Measurements and simulations show a double-sided realized gain of 11.8 dBi is achieved, excluding cable losses.

The first detection of the solar U+III association with an antenna prototype for the future lunar observatory

Abstract: We report about observations of the solar U+III bursts on 5 June of 2020 by means of a new active antenna designed to receive radiation in 4-70 MHz. This instrument can serve as a prototype of the ultra-long-wavelength radiotelescope for observations on the farside of the Moon. Our analysis of experimental data is based on simultaneous records obtained with the antenna arrays GURT and NDA in high frequency and time resolution, e-Callisto network as well as by using the space-based observatories STEREO and WIND. The results from this observational study confirm the model of Reid and Kontar (2017).

Creation and approbation of a low-frequency radio astronomy antenna for studies of objects of the universe from the moon's farside

Abstract: Purpose: Theoretical and experimental studies of the active antenna – an element of the low-frequency radio telescope antenna array for the future observatory on the farside of the Moon. Design/methodology/approach: To study the active antenna, consisting of a complex-shaped dipole and a low-noise amplifier, we used its mathematical model in the form of a two-port network, whose electrical parameters are set by the scattering matrix, the noise parameters being set by the covariance matrix of the spectral densities of noise waves. This model allows ma[1]king the correct analysis of the signal-to-noise ratio at the active antenna output with account for the external and internal noise sources. The modelling results were compared with those of experimental measurements of antenna characteristics. A series of radio astronomy observations were made with the developed antenna under the Earth environmental conditions. Findings: A numerical analysis of the radio telescope active antenna parameters has been made in a wide frequency range of 4–40 MHz. Two versions of the low-noise amplifier were developed to operate in the active antenna under the space and Earth environmental conditions. Under the Earth conditions, it has been experimentally proven that the range of problems, which such radio telescopes can effectively solve at low frequencies, is quite wide – from the solar research to the search for cosmological effects. Conclusions: The results of numerical simulations and experimental measurements obtained in this work have shown a satisfactory agreement between them for the most of the frequency range. The results of this work can be useful in the research and development of active antennas designed for operation at the decameter and hectometer wavelength ranges, particularly those intended for using under the space environmental conditions. Keywords: active antenna, Moon, radio astronomy observations, sensitivity

Specificity Analysis for Nonlinear Distorted Radiation Using 4.65GHz Band Massive Element Active Antenna System for 5G and Influence on Spatial Multiplexing Performance

Abstract: This paper reports the evaluation and simulated results of the nonlinear characteristics of the 4.65GHz Active Antenna System (AAS) for 5G mobile communication systems. The antenna element is composed of ±45◦ dual polarization shared patch antenna, and is equipped with total 64 elements with horizontal 8 × vertical 4 × 2 polarization configuration. A 32-element transceiver circuit was mounted on the back side of the antenna printed circuit board. With the above circuit configuration, a full digital beamforming method has been adopted that can realize high frequency utilization efficiency by using the Sub6GHz-band massive element AAS, and excellent spatial multiplexing performance by Massive MIMO has been pursued. However, it was found that the Downlink (DL) SINR (Signal to Interference and Noise Ratio) to each terminal deteriorated because of the nonlinear distorted radiation as the transmission output power was increased in the maximum rated direction. Therefore, it has been confirmed that the spatial multiplexing performance in the high output power region is significantly improved by installing DPD. In order to clarify the affection of nonlinear distorted radiation on spatial multiplexing performance, the radiation patterns were measured using OFDM signal (subcarrier spacing 60kHz × 1500 subcarriers in 90MHz bandwidth) in an anechoic chamber. And by the simulated analysis for the affection of nonlinear distortion on null characteristic, the accuracy of nulls generated in each user terminal direction does not depend on the degree of nonlinearity, but is affected by the residual amplitude and phase variation among all transmitters and receivers after calibration (CAL). Therefore, it was clarified that the double compensation configuration of DPD and high-precision CAL is effective for achieving excellent Massive MIMO performance. This paper is based on the IEICE Japanese Transactions on Communications (Vol.J102-B, No.11, pp.816–824, Nov. 2019). key words: 5G, AAS, Massive MIMO, DPD, CAL

The first detection of the solar U+III association with an antenna prototype for the future lunar observatory

Abstract: We report about observations of the solar U+III bursts on 5 June of 2020 by means of a new active antenna designed to receive radiation in 4-70 MHz This instrument can serve as a prototype of the ultra-long-wavelength radiotelescope for observations on the farside of the Moon Our analysis of experimental data is based on simultaneous records obtained with the antenna arrays GURT and NDA in high frequency and time resolution, e-Callisto network as well as by using the space-based observatories STEREO and WIND The results from this observational study confirm the model of Reid and Kontar (2017)

Four Knife-Edge Diffraction With Antenna Gain Model for Generic Blockage Modelling

Abstract: With the recent adoption of millimeter-wave spectrum in cellular communications, deployment of active antenna arrays and use of beamforming become vital to compensate for the increased path loss. However, directional high-frequency signals may suffer heavy attenuations due to blockage effects. Therefore, blockage modelling that adequately incorporates the effects of beamforming becomes increasingly relevant. We propose a Four Knife-Edge Diffraction with antenna Gain (4KED-G) model, a deterministic approach to model blockage with broad applicability. The 4KED-G model advances upon the existing models in its inclusion of both angular antenna gains and the diffraction from all the four edges of a rectangular screen blocker, leading to a more general and flexible blockage modelling approach compared to existing widely accepted blockage models. We theoretically show that the proposed generalised model incorporates the strengths of these existing models, while overcoming their shortcomings in establishing applicability to wider range of blockage scenarios. We validate the generalised model against known knife-edge diffraction blockage models for specific scenarios.

New Design Approach of a “2.4 GHz” Slotted Rectangular Patch Antenna with a Wideband Harmonic Suppression

Abstract: The designing of an antenna with a wideband harmonic suppression will lead to enhance the overall antenna performance efficiency as well as neglecting electromagnetic noises. A “defective ground superimposing” or a Y-slot construct confederated with a ring hopefully meets an effective approach that is exploited in removing high level of harmonics in the design process. A “2.4 GHz” rectangular U-slot microstrip patch antenna with an active antenna radiators and harmonic suppression grid has been presented. The paper focuses on the geometrical of active integration antennas to achieve efficient filtering and easy attenuation of unwanted harmonics. Further, an embedded empirical antenna with a high-order harmonic suppression has been suggested. This is followed by a “complementary opening recoiled construct cell”. The proposed approach was developed to control the antenna harmonics at center frequency of " $$2.4 \;{\text{GHz}}$$ ." The simulation sketches show that the reflection coefficient of multiple harmonics had an effective suppression up to 3.2 dB without any effect on the resonant frequency. The radiation patterns at high suppression levels of harmonics are within the range (13.92–15.2 dB) for both E-plane and H-plane. Further, the designed antenna bandwidth at the resonant frequency is $$\left( {85\;{\text{MHz}}} \right)$$ . Finally, the proposed antenna with $${\text{DGS}}$$ had return losses and antenna gain of $$\left( { - 23.15 \;{\text{dB}};\;8.25\;{\text{dB}}} \right),$$ respectively.

A Design Concept of Power Efficient, High Gain Antenna System for mm-Waves Base Stations

Abstract: A design concept for a phased-array-fed reflector antenna system intended for millimeter-wave base stations is presented. This concept is motivated by the need for efficient beamforming antenna systems with reduced power consumption as compared to the presently considered fully-populated large-scale MIMO arrays. The main idea is to use a high-gain reflector antenna to maximize the effective isotropic radiated power. That in turn, allows minimizing the number of active antenna elements of the phased-array feed, and hence limit the total supplied power. The proposed reflector antenna system is based on a torus reflector which is illuminated by an offset phased-array feed. We show how to determine the antenna design parameters to achieve the desired cell coverage.

Energy Efficiency Maximization Precoding for Quantized Massive MIMO Systems.

Abstract: The use of low-resolution digital-to-analog and analog-to-digital converters (DACs and ADCs) significantly benefits energy efficiency (EE) at the cost of high quantization noise in implementing massive multiple-input multiple-output (MIMO) systems. For maximizing EE in quantized downlink massive MIMO systems, this paper formulates a precoding optimization problem with antenna selection; yet acquiring the optimal joint precoding and antenna selection solution is challenging due to the intricate EE characterization. To resolve this challenge, we decompose the problem into precoding direction and power optimization problems. For precoding direction, we characterize the first-order optimality condition, which entails the effects of quantization distortion and antenna selection. For precoding power, we obtain the optimum solution using a gradient descent algorithm to maximize EE for given precoding direction. We cast the derived condition as a functional eigenvalue problem, wherein finding the principal eigenvector attains the best local optimal point. To this end, we propose generalized power iteration based algorithm. Alternating these two methods, our algorithm identifies a joint solution of the active antenna set and the precoding direction and power. In simulations, the proposed methods provide considerable performance gains. Our results suggest that a few-bit DACs are sufficient for achieving high EE in massive MIMO systems.

Over-the-Air Calibration of Active Antenna Arrays Using Multisine

Abstract: A novel over-the-air (OTA) beamforming calibration procedure is proposed, which can be applied to different types of multiple-input multiple-output (MIMO) transmitting antennas. The method consists of using two tones on each antenna element, the main tone, and the tickle tone. The latter one operates in a different frequency for each antenna element and is used to obtain the optimum phase that needs to be set for each element to generate a beam in the desired direction, at the main tone frequency. The novel method was applied to linear, planar, 3-D antennas, and noncollocated multiantennas to validate its applicability to different antenna types. Line-of-Sight (LOS) and non-LOS experimental results demonstrate that the method can be used to retrieve the required phase to fully control the antenna radiation pattern. An optimum radiation pattern and lowest error vector magnitude (EVM) can be achieved even under high multipath effects/non-LOS conditions. A comparison between the performance and the application of the array factor (AF) theory is presented for practical indoor scenarios, demonstrating the effectiveness of the method. It is demonstrated that the method may be an alternative to the calibration of nonstandard MIMO antennas, where the AF computation is complex or not possible.

Microstrip patch antenna with class-F load and DC block function for microwave power transfer

Abstract: This study proposes a novel microstrip patch antenna for microwave power transfer that functions as a class-F load and DC block. These functions enable a direct connection between an antenna and a power device (field-effect transistor) without using a class-F load circuit and capacitor for a DC block. In numerical simulations of a 2.45-GHz antenna, a reflection coefficient is -21.27 dB at the fundamental frequency, and a reflection coefficient and phase at the 3rd harmonic frequency are -0.99 dB and -1.4o, respectively. The simulated gain is 5.59 dBi at 2.45 GHz.

Optical true time delay pool based hybrid beamformer enabling centralized beamforming control in millimeter-wave C-RAN systems

Abstract: Effectively supporting millimeter-wave (mmWave) beamforming is still a major challenge in 5G cloud radio access network (5G C-RAN) systems with evolved common public radio interface-based (eCPRI-based) fronthaul. Herein, an optical true time delay pool based hybrid beamforming (OTTDP-HBF) scheme, enabling centralized beamforming control, is proposed for mmWave 5G C-RAN systems. The weight control of the OTTDP-HBF is physically implemented by a pre-designed optical wavelength matrix which is mapped from a series of optical carriers. After introducing optical true time delay, this optical wavelength matrix then maps to the defined OTTDP. In this scheme, all physical implementation and the computational processing of analog beamforming can be centrally deployed into a centralized unit or distributed unit (CU/DU). Each active antenna unit (AAU) therefore becomes very simple. For single-user and multi-user scenarios, the OTTDP-based hybrid precoders are formulated respectively. In the developed OTTDP-based multi-user hybrid precoder, the spectral efficiency is improved by making use of all RF chains. For a 9-element uniform planar array deployed at an AAU, a designed example of the OTTDP-HBF is presented, where spectral efficiency curves obtained via different precoding schemes for single-user and multi-user scenarios are compared and discussed respectively.

A compact, dual-polarized patch antenna with improved Tx–Rx isolation for 2.4 GHz single frequency full-duplex applications

Abstract: A compact dual-polarized monostatic antenna (single radiator for transmit and receive modes) is presented with differential receive mode operation to achieve excellent interport isolation for 2.4 GHz single frequency full-duplex or in-band full-duplex applications. The presented antenna comprises three ports radiating element (patch) and a simple 3 dB/180o ring hybrid coupler has been utilized for differentially excited receive mode operation. The 3 dB/180o ring hybrid coupler acts as a self-interference cancellation (SIC) circuit for effective suppression of RF leakage from the transmit port to provide very high interport decoupling between transmit and receive ports. A compact antenna structure has been realized by using two-layered printed circuit board through vias interconnections of both receive ports of the antenna with inputs of SIC circuit. The validation model of proposed antenna offers more than 95 dB peak interport isolation. Moreover, the experimentally measured interport isolation is better than 70 dB throughout the antenna's 10 dB return-loss impedance bandwidth (BW) of 50 MHz (2.38–2.43 GHz). Furthermore, the recorded isolation is more than 80 dB in 20 MHz BW. The implemented antenna has good radiation characteristics including nice gain and low cross-polarization levels as endorsed by measurements. Same antenna structure with microstrip-T feeds can provide DC isolated ports with same interport RF isolation performance for active antenna applications. Such antenna with DC interport isolation will avoid the requirements of additional series capacitors on transmit and receive ports of antenna.

Quiet Zone Quality of a Plane Wave Generator inside an Over-Moded Waveguide Chamber Emulating a Variable Angle of Incidence

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.

On the Power and Beam Dependency of Load Modulation in mmWave Active Antenna Arrays

Abstract: Linearization of active antenna arrays is gaining increasing interest due to their wide applicability in 5G New Radio (NR) networks. As direct access to the output ports of the power amplifiers (PAs) in highly integrated millimeter-wave (mmW) active arrays is difficult, different over-the-air (OTA) digital predistortion (DPD) solutions have been recently proposed. Large majority of such solutions build on the assumption that the nonlinear behaviors of the parallel PA units are independent of the beam direction. However, in this paper, we show through comprehensive OTA measurements on a commercial 64-element active array operating at 28 GHz, that the nonlinear distortion characteristics and the involved load modulation phenomenon largely depend on the beam direction as well as on the considered transmit power, and also that the beam-dependence increases with increasing transmit power. The findings of the measurements are also connected to the state-of-the-art PA models, paving the way towards the development of more efficient DPD solutions and the associated parameter learning methods for mmW active antenna array transmitters.

Cell Partitioning Antenna System Performance in Multi-User Scenarios for mmWave Communications

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.

Effect of UE Height on 3D Angular Spread of Correlated MIMO Channel

Abstract: In the forthcoming fifth generation (5G) architecture, full dimension MIMO (FD-MIMO) for enabling high network capacity wireless cellular system is been proposed. FD-MIMO provide beam control in azimuth and elevation plane using active antenna system (AAS) to take advantage of 3D-MIMO techniques such as 3D beamforming. It is therefore necessary to characterize and model channel parameters in 3D domain rather than the current 2D domain used for today’s cellular systems. In this work, using the REMCOM Wireless Insite X3D ray tracing engine, we characterize the mmWave MIMO channel at 28 GHz center frequency and 100 MHz bandwidth in terms of the angular spread (AS) using a 4 x 4 cross-polarized uniform planar array (UPA) at the base station and 2 x 2 MIMO antenna at the small cell receivers. Two scenarios were considered which are the street canyon and the high-rise. We provide 3D models for angular spread of arrival (at the receiver) and departure (at the base station). We obtain the cross-correlation coefficients of the parameters and analyze the effect of BS-UE height on AS.

Fully Generalized Spatial Modulation utilizing Transmit Antenna Grouping

Abstract: One of the recently modified multiple-input multiple-output (MIMO) systems is the spatial modulation (SM) Although SM is considered as MIMO in its composition, a single antenna at the transmitting side is activated at any time instant Among all transmitting antenna, the selection of this active antenna isn't random but rather chosen based on extra bits, called spatial bits, transmitted besides the conventional digitally modulated bits In addition to the transmission of additional bits, SM wireless communication system achieves an enhanced power efficiency, low error rate, low complexity at receiver, and completely inter-channel interference (ICI) elimination On the other side, SM suffers from the dramatic increase in the number of required transmit antennas to achieve a small improvement in data rate and low spectral efficiency when compared with multiplexing MIMO (Mux-MIMO) The exponential increase in the data rate of the SM scheme became linear thanks to the fully generalized spatial modulation scheme (F-Gen-SM) Although the F-Gen-SM scheme overcame one of the SM disadvantages, the achievable data rate still low when compared with Mux-MIMO Grouping generalized spatial modulation scheme (Gr-Gen-SM) tries to find a compromise between the advantage of SM and the high spectral efficiency of Mux-MIMO Gr-Gen-SM achieves high spectral efficiency but loses most of the SM advantages This paper introduces a new F-Gen-SM scheme utilizing the idea of dividing transmit antennas into groups (F-Gr-Gen-SM) This proposed scheme provides an improvement on data rate while preserving the advantages of SM as much as possible

Smart mmwave c-v2x antenna

Abstract: The present invention provides a smart mmwave C-V2X antenna. A vehicle includes a millimeter wave (mmWave) antenna, including a millimeter wave (mmWave) antenna, including a plurality of light elements and a plurality of active antenna elements in a predefined configuration surrounding a lensless camera element. The vehicle further includes an antenna controller configured to receive an image of asecond mmWave antenna of a second vehicle via the lensless camera of the mmWave antenna, identify a scale and angle of rotation between the mmWave antenna and the second mmWave antenna based on the image, compute phase angles for the active antenna elements of the mmWave antenna according to the scale and angle of rotation, and transmit data using the active antenna elements to the second vehicle, according to the computed phase angles, to form a beam targeted at the second mmWave antenna of the second vehicle.

Multi-cell, Multi-user, and Multi-carrier Secure Communication Using Non-Orthogonal Signals’ Superposition with Dual-Transmission for IoT in 6G and Beyond

Abstract: Considering the advancements of the internet of things (IoT) in 6G and beyond communications, data transmission security in IoT devices has received extensive interest because of their significant features, such as low computational complexity, led by low power requirements In such devices, the conventional cryptographic techniques may fail to provide secure communication To fight this drawback, physical layer security (PLS) has remarkable potential to provide security solutions suitable for such applications In this work, a highly effective PLS technique is proposed for providing secure communication against external and internal eavesdroppers in a downlink multi-cell, multi-user, and multi-carrier IoT communication system In our proposed system, we considered two base stations, where each base station uses a single radio frequency (RF) chain to link two antennas that are used for the transmission of data Further, we transmit the data in two rounds, and each round of transmission occurs through a single active antenna of each base station A different antenna is used for each round of transmission to communicate with two single antenna IoT devices/users in the presence of a passive eavesdropper In the proposed algorithm, frequency selective channel-based pre-coder matrices and the dual transmission approach are jointly employed The dual-transmission is performed simultaneously from two base stations to provide security against internal and external eavesdroppers The proposed system is suitable for IoT-based applications Also, the potential capabilities of our proposed algorithm are proved by extensive mathematical and simulation analysis

Power Efficiency and Linearity of Highly Integrated Transmitting Array Antennas

Abstract: Energy efficiency of 5G communication networks and beyond is a major challenge that is yet solved due to high power consumption and low linearity of massive array transmitters. This paper contributes to the existing framework of research in this area—that is today mainly dominated by the RF-component level and algorithmic solutions—by investigating various possible design trade-offs for highly-integrated active antenna elements as employed in such array transmitters. We demonstrate how to exploit antenna element design to synthesize the optimal loading conditions of a given power amplifier (PA) to, e.g., maximize its power-added efficiency (PAE), minimize nonlinear behavior, or find the desired trade-off between both. The numerical example with a K-band PA-integrated antenna element illustrates that moderate nonlinear effects of the PA can be significantly reduced (with up to 10–20 dB in third-order intermodulation distortion) by tuning the antenna design, with a relatively small PAE loss (< 5%). The effects of antenna array mutual coupling and corresponding cross-talk between PAs when beamsteering are discussed for a small-scale linear array of such elements.