Array Antenna System Research Articles

A Complexity-Efficient Quantum Architecture and Simulation for Eigen Spectrum Estimation of Vandermonde System in a Large Antenna Array

Vandermonde matrix finds a wide range of applications in the digital signal processing domain including antenna array processing. Eigenspectrum estimation remains a challenge in such a system when the matrix dimension increases. This precise problem can be well addressed in a quantum simulation framework based on quantum Hamiltonian simulation (QHS). However, the structural exploitation of the matrix is never considered, which can give benefits in terms of quantum gate complexity. In this work, we exploit the special structural property of a dense Vandermonde matrix by decomposing it into several sparse matrices and then use them for a complexity-efficient eigenvalue spectrum estimation in a quantum framework. In this context, we propose an iterative quantum simulation framework for a Vandermonde-structured Hamiltonian called quantum Vandermonde simulation (QVS). The proposed approach requires fewer quantum gate operations compared to the standard QHS of a dense Vandermonde matrix. In this work, we have considered a large antenna array system, that exploits a delay Vandermonde matrix (DVM) to create a multi-beam beamformer using the proposed low complex quantum architecture. Extensive theoretical and numerical analysis in terms of complexity and other quality parameters have been conducted to show the benefit of the proposed method.

Analysis and design of sub-6 beam steerable antenna array using meta-material loaded vivaldi elements

In this paper, a sub-6 beam-steerable antenna array system is introduced. The main radiating element in the proposed array is a gain-enhanced Vivaldi antenna, whose overall realized gain is improved by introducing near-zero-index metamaterial (NZIM) with broadband characteristics at 3.6 GHz. The proposed system is intended to be integrated with fifth-generation automotive applications. The 4 × 4 butler matrix is resonating at 3.6 GHz to feed the designed antenna array elements and steer the radiating beam. When altering the phase of the input signal, the primary beam direction is steered at an angle from 45° to 135°. So, by choosing the butler matrix input port, the phase of each radiating element is changed, which leads to precise beam direction control. All the system components, including antenna elements and the [4 × 4] butler matrix, are designed, simulated, and optimized. In order to verify the proposed design, the system is fabricated using the photolithographic technique. The experimental results show very good agreement with the simulated ones. The NZIM-loaded antenna element achieves a − 10 dB bandwidth of 2.9 GHz, while the overall array system achieves a 600 MHz bandwidth. The steered beam of the proposed system has an overall realized gain of 11.2 dB.

Precise RF Phase Measurement by Optical Sideband Generation Using Mach–Zehnder Modulators

A novel radio frequency (RF) phase measurement method that uses optical modulation was proposed. The mathematical model of Mach–Zehnder modulator (MZM) characterization was reviewed. By measuring the output sideband power of the optical modulator, the phase difference of the electric signals fed to the modulator was experimentally measured, and picosecond-level accuracies were achieved. This technique is expected to be useful for radio-over-fiber-based antenna array systems.

An efficient antenna system with improved radiation for multi-standard/multi-mode 5G cellular communications

This paper introduces a multi-input multiple-output (MIMO) antenna array system that provides improved radiation diversity for multi-standard/multi-mode 5G communications. The introduced MIMO design contains four pairs of miniaturized self-complementary antennas (SCAs) fed by pairs of independently coupled structures which are symmetrically located at the edge corners of the smartphone mainboard with an overall size of 75 × 150 (mm2). Hence, in total, the design incorporates four pairs of horizontally and vertically polarized resonators. The elements have compact profiles and resonate at 3.6 GHz, the main candidate bands of the sub-6 GHz 5G spectrum. In addition, despite the absence of decoupling structures, adjacent elements demonstrate high isolation. To the best of the authors’ knowledge, it is the first type of smartphone antenna design using dual-polarized self-complementary antennas that could possess anti-interference and diversity properties. In addition to exhibiting desirable radiation coverage, the presented smartphone antenna also supports dual polarizations on different sides of the printed circuit board (PCB). It also exhibits good isolation, high-gain patterns, improved radiation coverage, low ECC/TARC, and sufficient channel capacity. The introduced antenna design was manufactured on a standard smartphone board and its main characteristics were experimentally measured. Simulations and measurement results are generally in good agreement with each other. Moreover, the presented antenna system delivers low SAR with adequate efficiency when it comes to the appearance of the user. Hence, the design could be adapted to 5G hand-portable devices. As an additional feature, a new ultra-compact phased array millimeter-wave antenna with super-wide bandwidth and end-fire radiation is being introduced for integration into the MIMO antenna systems. As a result, the proposed antenna system design with improved radiation and multi-standard operation is a good candidate for future multi-mode 5G cellular applications.

Channel Estimation for RIS-Aided mmWave Massive MIMO System Using Few-Bit ADCs

Millimeter wave (mmWave) massive multiple-input multiple-output (massive MIMO) is one of the most promising technologies for the fifth generation and beyond wireless communication system. However, a large number of antennas incur high power consumption and hardware costs, and high-frequency communications place a heavy burden on the analog-to-digital converters (ADCs) at the base station (BS). Furthermore, it is too costly to equipping each antenna with a high-precision ADC in a large antenna array system. It is promising to adopt low-resolution ADCs to address this problem. In this letter, we investigate the cascaded channel estimation for a mmWave massive MIMO system aided by a reconfigurable intelligent surface (RIS) with the BS equipped with few-bit ADCs. Due to the low-rank property of the cascaded channel, the estimation of the cascaded channel can be formulated as a low-rank matrix completion problem. We introduce the Bayesian optimal inference framework to tackle with the information loss caused by quantization. To implement the estimator and achieve the matrix completion, we use efficient bilinear generalized approximate message passing (BiG-AMP) algorithm. Extensive simulation results verify that our proposed method can accurately estimate the cascaded channel for the RIS-aided mmWave massive MIMO system with low-resolution ADCs.

Deep Learning of Near Field Beam Focusing in Terahertz Wideband Massive MIMO Systems

Employing large antenna arrays and utilizing large bandwidth have the potential of bringing very high data rates to future wireless communication systems. However, this brings the system into the near-field regime and also makes the conventional transceiver architectures suffer from the wideband effects. To address these problems, in this paper, we propose a low-complexity frequency-aware beamforming solution that is designed for hybrid time-delay and phase-shifter based RF architectures. To reduce the complexity, the joint design problem of the time delays and phase shifts is decomposed into two subproblems, where a signal model inspired online learning framework is proposed to learn the shifts of the quantized analog phase shifters, and a low-complexity geometry-assisted method is leveraged to configure the delay settings of the time-delay units. Simulation results highlight the efficacy of the proposed solution in achieving robust performance across a wide frequency range for large antenna array systems.

Distributed Antenna in Drone Swarms: A Feasibility Study

Unmanned aerial vehicles offer a versatile platform for the realization of phased array antenna systems, enabling multiple antenna elements to be distributed spatially in an agile, flexible, and cost-effective manner. Deploying individual antenna elements on single drones and using a swarm of such drones to create an antenna array has the potential to be a disruptive technology. Antenna directivity is limited by the physical aperture size as compared to the wavelength of the radiation being transmitted/received, with electrically larger antennas giving a higher directivity at the cost of an increased size and weight. The authors presented a brief feasibility study using a simple mathematical model implemented in software to explore the predicted performance of the novel UAV deployed antenna array, the limitations of such a system, and the potential applications where such a capability would be beneficial. The authors concluded that it is possible to achieve a suitably coherent superposition of electromagnetic radiation at frequencies of ~1 GHz and lower with current global positioning technologies which offer centimeter scale positioning accuracy and with current drone positioning systems used to control drone swarms.

Minkowski–Sierpinski Fractal Structure-Inspired 2 × 2 Antenna Array for Use in Next-Generation Wireless Systems

In this paper, the design, simulation, fabrication, and characterization study of a low-cost and directional hybrid four-element (2 × 2 configuration) Minkowski–Sierpinski fractal antenna array (MSFAA) for the high-efficiency IEEE 802.11ax WLANs (Wi-Fi 6E) and the sub-6 GHz 5G wireless system is presented. Each element of the array is separated by 0.7 λ0. The complete four-element fractal antenna array system includes designing the single-element Minkowski–Sierpinski fractal antenna using two different substrates for performance comparison and an equal-split Wilkinson power divider (WPD) to achieve power division and to form a feed network. The single-element antenna, four-element fractal antenna array, and WPDs are fabricated using a flame-resistant (FR4) glass epoxy substrate with a dielectric constant (εr) of 4.3 and thickness (h) of 1.66 mm. For performance comparison, a high-end Rogers thermoset microwave material (TMM4) substrate is also used, having εr = 4.5 and h = 1.524mm, respectively. The designed four-element fractal antenna array operates at the dual-band frequencies of 4.17 and 5.97 GHz, respectively. The various performance parameters of the antenna array, such as return loss, bandwidth, gain, and 2D and 3D radiation patterns, are analyzed using CST Microwave Studio. The fabricated four-element antenna array provides the bandwidth and gain characteristic of 85 MHz/4.19 dB and 182 MHz/9.61 dB at 4.17 and 5.97 GHz frequency bands, respectively. The proposed antenna array design gives an improvement in the bandwidth, gain, and radiation pattern in the boresight at both frequencies. In the IEEE 802.11 ax WLANs (Wi-Fi 6E) deployments and the upcoming 5G wireless and satellite communication systems, it is critical to have directional antenna arrays to focus the radiated power in any specific direction. Therefore, it is believed that the proposed dual-band four-element fractal antenna array with directional radiation patterns can be an ideal candidate for the high-efficiency IEEE 802.11ax WLANs (Wi-Fi 6E) and the upcoming 5G wireless and satellite communication systems.

Uniform Linear Antenna Array Beamsteering Based on Phase-Locked Loops

Phased arrays are extensively used in many modern beam-scanning applications such as radar and satellite communications. Electronic beam scanning makes phased arrays an important aspect of modern antenna array systems. This Tutorial aims to promote the basic understanding of the principle and operation of a phased array to general undergraduate students. This paper starts with a discussion on the theory of operation and some basic definitions of antenna parameters followed by derivations of two-element and N-element array patterns and, finally, a five-element array design. The essential hardware based on Phase-Locked Loops (PLLs) as phase controllable RF sources required to build an array and the basic tools required for software and measurement set-up to demonstrate the beam-scanning phased array operation are presented. This enables students to quickly understand and set-up an experiment to verify the phased array operation with commercial off-the-shelf components. In addition, the hardware and software necessary for autonomous control are discussed. By combining basic concepts of phase arrays with a series of simple coding and intuitive laboratory experiments, students can easily understand the Uniform Linear Array (ULA) scanning operation.

Omni-Directional Pathloss Measurement Based on Virtual Antenna Array With Directional Antennas

Omni-directional pathloss, which refers to the pathloss when omni-directional antennas are used at the link ends, are essential for system design and evaluation. In the millimeter-wave (mm-Wave) and beyond bands, high gain directional antennas are widely used for channel measurements due to the significant signal attenuation. Conventional methods for omni-directional pathloss estimation are based on directional scanning sounding (DSS) system, i.e., a single directional antenna placed at the center of a rotator capturing signals from different rotation angles. The omni-directional pathloss is obtained by either summing up all the powers above the noise level or just summing up the powers of detected propagation paths. However, both methods are problematic with relatively wide main beams and high side-lobes provided by the directional antennas. In this correspondence, directional antenna based virtual antenna array (VAA) system is implemented for omni-directional pathloss estimation. The VAA scheme uses the same measurement system as the DSS, yet it offers high angular resolution (i.e. narrow main beam) and low side-lobes, which is essential for achieving accurate multipath detection in the power angle delay profiles (PADPs) and thereby obtaining accurate omni-directional pathloss. A measurement campaign was designed and conducted in an indoor corridor at 28-30 GHz to verify the effectiveness of the proposed method.

Practical Noise Model of an Active Electronically Scanning Array

Active electronically scanning arrays are now widely used in radar and communication systems. The noise characteristics are critical to the system signal-to-noise ratio, thus modeling of the antenna array noise is useful. In this paper, a two-port noise model of an active electronically scanning array is presented, which is more practical than the model in previous publications. In this model, an antenna array with a multistage combiner network is equivalent to a one-stage combiner network, thus the calculation of the noise figure is greatly simplified. Since the model is based on measurable parameters, it can be applied directly to the design of electronically scanning arrays. The noise model of a spaceborne synthetic aperture radar antenna system is displayed for example. Some useful conclusions are got about the noise figure for tapered antenna arrays. For a weighted antenna array with taper efficiency εT, if the gain of low noise amplifiers is sufficiently large, the noise figure of the antenna array is increased by 1/εT, compared to a uniformly weighted array. Besides, the deterioration of the signal-to-noise ratio for a tapered antenna array system originates from the increase of antenna noise temperature, rather than the decrease of antenna aperture gain.

High Accuracy Distributed Kalman Filtering for Synchronizing Frequency and Phase in Distributed Phased Arrays

Precise frequency and phase synchronization are among the important aspects in a coherent distributed phased array antenna system, and are among the most challenging to achieve for microwave frequencies and above. We propose a high accuracy distributed Kalman filter (HA-DKF) in which the nodes in the array perform consensus averaging on their locally shared measurements, the innovation noise covariances, and the KF-predicted as well as the KF-updated estimates and error covariances, yielding improved electrical state synchronization compared to other works in the literature. We evaluate the algorithm through simulation and show that it converges in fewer iterations and yields better electrical state synchronization than other algorithms.

Phased Array Antenna System Enabled by Liquid Metal Phase Shifters

Phased Array Antenna System Enabled by Liquid Metal Phase Shifters

Chip-Based Brillouin Processing for Microwave Photonic Phased Array Antennas

In this review paper, we provide perspectives on the implementation of high-performance, wideband, chip-based Brillouin microwave photonic processing subsystems for use in phased array antennas that require processing at every antenna element. We review recent advances in chip-scale Brillouin microwave photonic signal processing systems, including reconfigurable filters, frequency converters, tunable phase shifters, true time delays and microwave sources, which are key functionalities for phased array antennas. We discuss a roadmap for developments of Brillouin-based microwave photonic processors to reach the required performance and compact footprint for implementation in future dynamically reconfigurable phased array antenna systems.

Car Talk: Active Phased Array Antenna System Design for Vehicle-to-Everything Communication

Car Talk: Active Phased Array Antenna System Design for Vehicle-to-Everything Communication

A Low-Loss Defected-Ground-Structure Based Phase Shifter and Antenna on a 4-μm Thin Liquid Crystal Layer

In this paper, a liquid crystal (LC) phase shifter is proposed using a defected-ground-structure (DGS) transmission line on a 4-μm-thin LC layer. The DGS transmission line is a modified micro-strip line that improves phase shift and loss in a 4-μm-thin LC layer by partially removing the ground plane. The phase shift is achieved through the variation of the LC dielectric constant caused by the bias voltage of the DGS transmission line. The proposed DGS phase shifter exhibits the highest figure-of-merit (FoM) of 61.5°/dB at 30 GHz. Furthermore, the phase shifter exhibits an rms phase error of less than 20° at 26-30 GHz and a 1-dB compression point of 30 dBm with 2.5° phase error at 35 dBm. To demonstrate the feasibility of the LC-based antenna array systems, the DGS phase shifter is combined with a patch antenna, resulting in a gain of 0 dBi and 360° phase shift at 18 GHz. The thin LC layer and high FoM make the proposed DGS phase shifter a suitable solution for use in large phased array systems and reconfigurable intelligent surfaces.

A Phased Array Antenna System of a Millimeter-wave FMCW Radar for Blind Spot Detection of Mobile Robots

Mobile robots have been extensively used in manufacturing plants for inter-logistic transportation in recent years. This paper covers a phased array antenna design for a millimeter wave radar system to improve lidar-based navigation systems' safety and environmental consciousness. The K-band phased array antenna, when integrated with 24 GHz Frequency-Modulated-Continuous-Wave (FMCW) radar, not only enhances the accuracy of the 2-D Area Scanning lidar system but also helps with the safe operation of the vehicle. The safety improvement is made by covering blind spots to mitigate collision risks during the rotations. The paper first reviews the system-level details of the 2D lidar sensor and shows the blind spots when integrated into a Mobile Robot prototype. Then continues with the inclusion of an FMCW Low-Speed Ramp radar system and discusses the design details of the proposed K-band antenna array, which will be integrated with a radar sensor.

MIMO Antenna Array in 5G Communication

The main topics of this study are the fundamental operation of a MIMO antenna array and the benefits of using MIMO technology for 5G communication. Three significant works are recognized as benchmarks by outlining the component sets and spatial reuse that designers should consider in MIMO antenna design. For 5G low and medium frequencies, these include an 8x8 large-scale MIMO antenna array and a circular binary MIMO antenna array. In these designs, the design of the MIMO antenna array will be carried out based on the introduction of the design and parameter selection of the antenna array elements as a priority. Additionally, this study conducts a performance analysis of a multi-cell, Massive MIMO antenna array system, which serves as a high reference point for the Analysis of this system. Numerous possible application domains exist for the study object of this work, including hotspot situations and 3D coverage scenarios. Campus, shopping malls, and halls are examples of hotspot environments.

Reduction of mutual coupling in antenna array using metamaterial surface absorber

The reduction of direct coupling is an essential parameter in various MIMO and antenna array systems to minimize the interference between each element. In this article, the concept for reduction of mutual coupling between Vivaldi antenna arrays using metamaterial structure is proposed. The proof of concept for reduction of mutual coupling is presented using placement of metamaterial absorber at the intermediate distance between two directional end-fire antennas. The measured isolation between antennas with the aforementioned methodology is improved to 53.2 dB from 28 dB for the intermediate distance of 0.5λ0 between adjacent antennas. Further, the intermediate distance between the adjacent array elements is reduced to 0.25λ0 with an improved and acceptable mutual coupling of 37 dB. This will give the possibility to improve the resolution of an imaging array setup as the pixel size (distance between adjacent antennas) is getting reduced with decrease in separation distance between antennas.

Fast design technique for thinned linear array with arbitrary grid spacing in the presence of multi-constraint requirements

Global optimization algorithms can be performed to design thinned arrays with various beamshapes. However, they have intensive computational efforts and are therefore limited to small to medium sized array problems. On the other hand, analytical methods do not suffer from this problem, but usually assume an idealized environment, thereby excluding the influence of a complex electromagnetic environment on thinned array designs caused, e.g., by beam-scanning and interference signals. In this paper, a unified framework of the reconfigurable thinned array antenna system is developed and we propose a fast design technique for thinned linear arrays that is capable of dealing with the aforementioned limitations. It is based on the previously published by means of the modified iterative Chirp-Z transform (MICZT) technique, which is herein extended and generalized for linear array thinning with arbitrary grid spacing in the presence of multi-constraint requirements. More specifically, the fast computation of the scannable array factor for a uniformly illuminated thinned linear array is discussed, and beam-scanning thinned arrays with symmetry configuration are also exploited in this paper. In addition, thinned array designs with null placement will be investigated for rejecting multiple sidelobe interference signals. Several representative numerical examples and comparisons with existing methods are presented to validate the effectiveness and efficiency of the proposed technique.