Multi-element Antenna Research Articles

Quantitative assessment of the effectiveness of adaptive spatial processing algorithms in searching for low-noise underwater vehicles in surface shipping conditions of different density

The article describes the methodology and provides the results of a model quantitative assessment of the effectiveness of solving the problem of detecting and tracking a low-noise underwater object using three algorithms for spatial signal processing at the output of a multi-element antenna — the non-adaptive Bartlett algorithm, the Capon algorithm, and the Capon algorithm combined with a projection procedure limiting the signal power of strong local sources.

Design of a Tri-band Minkowski Fractal MIMO Antenna for FR2 5G Applications

The growing importance of fifth-generation (5G) communication technologies for the Internet-of-Things have made it necessary to design multi-element antennas that operate within the millimetre-wave spectrum. However, simultaneously achieving multiple operating frequencies, high gain and good isolation between the elements of such small-sized antennas is a challenging task. In this research, a composite right/left hand millimetre-wave fractal antenna was designed for 5G mobile terminals, in order to simultaneously satisfy these key design goals. This aim was accomplished by designing a 2 x 2 multiple-input, multiple output (MIMO) antenna based on the second-order Minkowski fractal using an electromagnetics simulation software, Computer Simulation Technology (CST) Studio Suite ®. Two composite-right/left hand structures were included on the reverse side of the antenna, to reduce the coupling between the MIMO antenna elements. Simulation results show that the designed antenna operates at three frequency bands within the millimetre-wave spectrum, namely 25.52 GHz – 28.23 GHz, 36.5 GHz – 37.5 GHz, and 47.7 GHz – 49.7 GHz. The maximum antenna gains at these three bands are 6.9 dBi, 7.5 dBi, and 6.0 dBi, respectively. Also, good isolation is realized between the antenna elements at the operating frequencies, with a minimum value of 10.8 dB. With a spacing of 0.03λ between the MIMO antenna elements, the overall size of the designed antenna was 30 mm x 12 mm x 0.508 mm, which compares positively with other related fractal antenna designs. The designed antenna shows good prospects for integration into various mobile terminal devices to aid 5G-based millimetre-wave communications.

Low-Profile Circularly Polarized HF Helical Phased Array: Design, Analysis, and Experimental Evaluation

This paper presents the design, development, and performance evaluation of a compact wideband phased array active helical antenna for monitoring HF interference. Traditional multi-element HF antenna designs are often subjected to size restrictions. The front-to-back ratio of the proposed circularly polarized phased array exceeds 20 dB across the operating range. This array enables the simultaneous monitoring of vertically and horizontally polarized signals, offering a practical alternative to larger antennas, particularly in space-constrained scenarios. Through advanced low-noise amplifier design, efficiency and bandwidth are optimized while mitigating mutual coupling effects. Optimal beamformer design enhances array performance with respect to more traditional array design approaches. The test results verify exceptional performance with an average axial ratio of 2 dB and a high front-to-back ratio beyond the desired frequency range. This study offers valuable insights into the design and deployment of compact wideband phased array antennas, providing an effective solution for monitoring HF interference.

Analysis of the approaches to protection against interference of UAV satellite navigation receivers.

The main approaches to the construction of signal receivers of global satellite navigation systems of unmanned aerial vehicles, protected from the influence of artificially created interference, are considered. Such systems are equipped with multi-element phased antenna arrays and devices of controlled reception pattern antenna. In the process of processing the received information signal by the Controlled Reception Pattern Antenna device. the selection of interference and their suppression (compensation) is ensured, which is equivalent to the formation of dips in the spatial pattern of the antenna array at the corners that correspond to the directions of the interference sources. The basic principles of the implementation of the adaptive algorithm for processing the received information signal are given. The design and composition of the navigation receiver of the «Orlan-10» unmanned aerial vehicle equipped with a Controlled Reception Pattern Antenna device is considered. A conclusion was made regarding the fundamental possibility of creating a domestic navigation receiver with a Controlled Reception Pattern Antenna device. In the future, it is envisaged to deploy works on the creation of Controlled Reception Pattern Antenna devices with a greater number of antenna elements and the use of optimization principles of the quantitative composition of adaptation operations, in order to ensure the performance of these devices with a greater number of simultaneously enabled sources of interference and higher levels of their signal power.

Characteristic mode based self isolated MIMO antenna design for millimeter wave 5G communications

The paper introduces a self-isolated quad-port multi input multi output antenna system designed for fifth-generation wireless communication. The reported antenna structure possesses an overall dimension of 12.4 × 12.4 × 0.508 mm3 and is derived from a single-element antenna, featuring a circular patch accompanied by a sectoral slot. To achieve the desired frequency band, an additional circular patch is purposefully placed over the main radiator. The development of each design stage in the antenna structure is investigated using the theory of characteristic mode. This configured multi-element antenna structure achieves a broad operational bandwidth spanning 4.5 GHz, encompassing frequencies from 26.1 GHz to 30.6 GHz, rendering the antenna well-suited for deployment in the millimeter-wave frequency bands of n257, n258, and n261 respectively. A total gain of 6.27 dBi is achieved with port isolation of −24 dB. Furthermore, the antenna undergoes validation for diversity metrics, including envelope correlation coefficient, diversity gain, channel capacity loss, total active reflection coefficient, and mean effective gain. The antenna is fabricated and experimentally validated with the simulated counterpart. Later, a comparative analysis has been conducted which revealed that the proposed antenna demonstrates > 80 % increase in compactness compared to existing antenna designs documented in the literature.

Multi-Element Self-Decoupled MIMO Patch Antenna With Flexible Characteristics

Multi-Element Self-Decoupled MIMO Patch Antenna With Flexible Characteristics

STRUCTURES OF ADAPTIVE SIGNAL PROCESSING SYSTEMS FOR RADAR SENSORS OF EXTERNAL INFORMATION FOR CORRELATION-EXTREME AIRCRAFT NAVIGATION SYSTEMS

During the guidance of the aircraft on the final part of the flight, it is affected, along with other external factors, by interferences of various (artificial or natural) origins. These interferences have various effects on the receiving elements of the antenna array of the radar sensor of external information. Due to the variability and rapidity of the complex interference situation, adaptive interference protection systems are the most effective in combating these interferences. It is known that the use of adaptive processing systems allows for overcoming the practically inevitable a priori uncertainty of statistical characteristics of signals and interference of various origins. At present, due to the development of digital technology, new methods and devices for adaptive signal processing against the back- ground of interference have appeared. Thus, the arsenal of methods of adaptation to Gaussian disturbances has been supplemented by methods involving the inversion (direct or recurrent) of the most plausible estimates of correlation matrices of disturbances or their regularized varieties. Wide possibilities of adaptation are opened up in modern radar stations with multi-element phased antenna ar- rays, which provide for digital information processing. Due to the very high speed of the aircraft during the operation of its correlation- extreme guidance system, as well as due to the dynamic and non-stationary interference environment, an important requirement for adaptive anti-jamming systems is their speed. The effectiveness of adaptive processing of signals against the background of interference can be significantly increased by using reliable a priori information. The paper considers a method of increasing the speed of adaptive protection systems against radar interference of various origins by taking into account a priori information about the central symmetry of the receiving channels of radar sensors of external information of correlation-extreme aircraft navigation systems. It is shown that taking into account such a priori information as the central symmetry of the receiving channels of radar sensors of external informa- tion leads to a corresponding change in the structure of devices for adaptive signal processing in the conditions of interference in these sensors and as a consequence, to an increase in their speed.

Address direction finding of ZigBee devices

Statement of problem. The active use of wireless technologies requires the development of means of monitoring devices and data transmission networks and, in particular, ZigBee wireless personal networks. Therefore, the detection and localization of working ZigBee devices is an urgent task of radio monitoring services. Correlation-interferometric direction finders based on two-channel radio receiving equipment cyclically connected to various pairs of elements of a multi-element antenna system can serve as a tool for bearing radio signals. For the direction finding of packet radio signals, the direction finder accumulates time samples from different antenna pairs over long time intervals; joint processing of these data allows determining the direction of arrival of radio signals. An obstacle to the direction finding of ZigBee devices is the fact that many similar devices can simultaneously operate in the same frequency range, generating a chaotic alternation of packets in the air. As a consequence, the accumulation of information from a specific ZigBee device for different antenna pairs of the direction finder becomes problematically. Purpose of the work is to develop a method for joint identification and bearing of detected devices of ZigBee networks. Results. the presented method of address bearing is implemented on the basis of the mobile direction finder ARTICLE-M, used to search for and locate unauthorized sources of radio emissions, and allows detecting signals of the 802.15.4 standard, identifying personal network devices, as well as forming estimates of directions to these sources of radio emissions. Practical importance. the use of address bearing of ZigBee network devices increases the functionality of existing radio monitoring equipment, and also allows the localization of unauthorized radio sources masquerading as Internet of Things devices.

Detection and analysis of Wi-Fi signals for address direction finding

Statement of problem. The active use of wireless technologies requires the development of radio equipment that monitors devices and data transmission networks and, in particular, wireless local area networks of the 802.11 standard (Wi-Fi). The need to identify unauthorized access points and subscriber devices of these networks, including their bearing and localization, is an urgent task of radio monitoring services. Correlation-interferometric direction finders based on a two-channel radio receiving equipment cyclically connected to various pairs of elements of a multi-element antenna system are an effective tool for bearing radio signals. For the direction finding of packet radio signals, direction finders accumulate time samples from different antenna pairs over long time intervals; joint processing of these data allows determining the direction of arrival of radio signals. However, in the frequency range of transmission of signals of the IEEE 802.11 standard, many sources carry out parallel transmission of information in the time-sharing mode, therefore, the direct accumulation of samples entails mixing and combining data generated by different sources. This causes gross bearing errors and requires the development of new ways of joint identification and bearing of packet radio signals. The purpose of the work is to propose a method for determining the identification features of access points and subscriber devices of Wi-Fi networks, which allows combining fragments of data samples when bearing radio sources. Results. The presented method of address bearing, focused on signals of the 802.11 standard, allows detecting OFDM signals, identifying access points and subscriber devices of the local network and forming an estimate of the direction to these sources of radio emissions. Practical importance. The use of address bearing of Wi-Fi network devices increases the functionality of existing analyzers. The presented method of address bearing is implemented based on the mobile direction finder ARTICLE-M [1], which is used in search and localization systems of unauthorized sources of radio emissions.

A novel MIMO antenna with switchable UWB/5G modes for vehicular terminals

AbstractThis paper demonstrates the design and development of a dual‐operating mode multiple‐input and multiple‐output (MIMO) antenna. The MIMO antenna comprises a novel ultrawideband (UWB) antenna with selectively chosen feedlines to obtain bandwidth reconfiguration. The novel UWB monopole evolved from a rectangular monopole whose radiating portion and the ground plane are shaped to obtain broadband impedance matching from 2.3 to 10.7 GHz (Mode 1). The antenna is excited using a 50‐Ω microstrip line. An additional feed path is created and deployed to achieve bandwidth selectivity with a tuning fork bandpass filter (BPF) operating between 2.8 and 4 GHz. Bandwidth selection is performed using a pair of positive–intrinsic–negative diodes. Thus, in the reconfigured state, the monopole is connected to the excitation source through the BPF, restricting the operational bandwidth to 2.8–4.0 GHz (Mode 2). A vertically polarized four‐element MIMO antenna with pattern diversity characteristics is constructed, and the performance parameters are studied. The proposed multiantenna is fabricated and tested in the laboratory. The proposed MIMO antenna offers a measured gain of over 3.51 dBi and total efficiency above 78%. The proposed multielement antenna is suitable for UWB communications, including ISM, LTE2700, and sub‐6 GHz 5G communications at 3.5 GHz in the vehicular environment.

Wideband coupling suppression with neutralization-line-incorporated decoupling network in MIMO arrays

In this paper, a novel neutralization-line-incorporated decoupling network (NLDN) is proposed for wideband multielement antenna arrays. Through introducing additional current path supplied by neutralization line (NL) between antenna elements and decoupling network (DN) between feeding lines but without extra matching network to counteract with the original path, the wideband antenna arrays are well matched and isolated based on network model derivation and node analysis. Four pairs of prototypes are designed to verify the decoupling effectiveness, including two-element symmetric H-plane and asymmetric E-plane coupled antenna arrays, one-dimensional linear and two-dimensional planar ones. Accordant simulated and measured results reveal that the proposed NLDNs for four examples can suppress mutual coupling to below −20 dB in over 20.6% bandwidths, with broadside gains increased, radiation patterns improved, envelope correlation coefficients decreased and total efficiencies enhanced. On account of its followable design process, implementable configuration and wideband decoupling capability, the approach has the potential to be employed in large-scale wideband MIMO antenna arrays.

Spatial Multi-Source Information Fusion Localization Algorithm in Non-Line-of-Sight Environments

In this paper, a high-accuracy localization problem under a complex non-line-of-sight (NLOS) condition is addressed by a new method that utilizes multiple NLOS paths to improve localization accuracy, as opposed to the traditional method of suppressing them. The spatial multi-path array fusion localization model is presented and analyzed, followed by an angle-of-arrival (AOA) and time-of-arrival (TOA) algorithm based on spatial multi-information fusion that seeks to improve localization accuracy. Multi-path of spatial signals, measurement of the multi-element antenna, and geographic environment information are integrated into the proposed method for localization optimization. Simulation experiments were carried out, and the results revealed that the proposed algorithm is capable of making full use of spatial multi-location information for localization, thus improving the accuracy of localization in a the NLOS environment effectively and increasing the locatable probability of complex environment localization applications.

Three-element circularly polarized MIMO antenna with self-decoupled probing method for B5G-V2X communications

In this article, a three-element circularly polarized multiple-input-multiple-output (CP-MIMO) antenna array with self-decoupled probing method is introduced. Three unidirectional radiated Guo-shaped patch antennas were arranged in a triangular lattice and excited by L-shaped feeding probes at different locations with respect to the patch center. Meanwhile, the patches themselves remained artistic and were placed in the upward position. Namely, the main motivation is to generate CP directional beams without requiring orthogonal placement. The contributions of this work account for (i) spatial diversity, (ii) pattern diversity, (iii) polarization diversity, and (iv) enhanced isolations (25 dB) between patch elements without inserting any external decoupling structures. As such, the antenna efficiency of Guo-patch elements can be raised in an order of 90 % within the band of interest at IEEE 802.11n/g/ac, viz., 2.4–2.5 GHz. The CP-MIMO prototype was fabricated and validated with experimental tests. Outstanding performance metrics such as an envelope correlation coefficient (ECC) of 0.005, mean effective gain (MEG) of −3.5 dB, channel capacity loss (CCL) of 0.18b/s/Hz, and a total active reflection coefficient (TRAC) of better than −15 dB were obtained. The measured results, which agreed with theoretical simulations, confirmed that the multi-element MIMO antenna with the spatial-, pattern- and polarization-diversity is a good candidate for the multi-user B5G-V2X.

Double-Directional Time-Spatial Measurement Method Using Synthetic Aperture Antenna

The 5th-generation mobile communication uses multi-element array antennas in not only base stations but also mobile terminals. In order to design multi-element array antennas efficiently, it is important to acquire the characteristics of the direction of arrival (DOA) and direction of departure (DOD), and a highly accurate and simple measurement method is required. This paper proposes a highly accurate and simple method to measure DOA and DOD by applying synthetic aperture (SA) processed at both Rx and Tx sides. It is also shown that the addition of beam scanning to the proposed method can reduce the measurement time while maintaining the peak detection resolution. Moreover, experiments in an anechoic chamber and a shielded room using actual wave sources confirm that DOA and DOD can be detected with high accuracy.

Methods and Algorithms of Subsurface Holographic Sounding

In our experiments, we develop and test portable multi-element receiver antenna arrays, electrically scanned in order to immediately obtain a recognizable image of subsurface objects. Two quadrature components of the radar return signal are processed with a Kirchhoff backward migration algorithm. Physical theory is used to assess the quality of the holographic image, and the synthetic aperture approach is developed and tested. The parabolic wave equation and Gaussian beam technique are used in order to take into account refraction effects and to suppress specular reflection from the air-ground interface. Laboratory and field tests confirmed the predicted device parameters.

Photonic Delay Processing With Centralized Etalon Cascade for Radio Beamsteering in Simplified 2 × 5 Phased-Array Radio Heads

The adoption of beam-centric radio communication schemes calls for efficient methods of beamforming with multi-element antennas. We present a delay generation method that employs a shared and centralized cascade of Gires-Tournois etalons for element-by-element radio frequency beamsteering at remote radio heads, thus adding no complexity at the antenna site. We experimentally demonstrate beamsteering of up to 32° in combination with a 2 × 5 phased-array antenna operated at a radio carrier frequency of 3.5 GHz and transmitting 64-ary quadrature amplitude modulated, orthogonal frequency division modulated radio signals. The radio transmission performance over mobile optical fronthaul and free-space radio propagation is evaluated through offline error vector magnitude estimation and real-time transmission of high-definition video traffic. We further show carrier phase switching at 2 kHz using direct emission frequency modulation of the involved optical light sources, proving the proposed concept to support the fast tracking of mobile users.

DoA Estimation With a Single Antenna and a Few Low-Cost Backscattering Tags

Backscatter radio utilizes the reflection that an electromagnetic wave undergoes when it impinges an unmatched-to-a-load antenna, in order to achieve ultra-low-power communication. This work exploits principles commonly found in the ultra-low-power, backscatter communication literature, offering multi-element array functionalities to a single-antenna receiver. A small number of simple, switching backscattering tags deployed in space, emulate a distributed, multi-element antenna array by copying a transmitter’s signal to distinct frequency bands. A receiver can then obtain independent observations of the same signal by discriminating said bands. Using the backscatter tag-based array, the direction of arrival (DoA) estimation problem is addressed without the cost of multiple RF front ends or hardware modifications, at either end of a wireless communication link. The feasibility of the idea was examined through both simulations and experimental deployments. An absolute error of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\approx 20$ </tex-math></inline-formula> degrees was observed when utilizing 5 custom-built backscattering tags, while simulations showed that more than 10 tags can offer error of less than 5 degrees.

Switching-Based Selection Techniques for Tripolar Antennas in Multihop IoT Networks

Adaptive multielement antennas can be leveraged to improve the reliability of wireless systems deployed in cluttered, depolarizing environments, such as those expected for Internet of Things (IoT) applications. While the performance improvement provided by such antennas has been well studied for individual links, multiple-hop networks have received little attention. In this work, we consider the problem of how devices in a multihop network should configure a three-element, tripolar antenna when deployed in a Rayleigh fading environment. We propose two switching-based antenna selection strategies: 1) Max-Sum and 2) Max–Min, each of which considers the channel conditions for communicating to nodes both higher and lower in the network hierarchy. We first derive the outage performance of the proposed schemes analytically and compare their performance with the well-known approaches of selection and switched diversity. Through simulations, which utilize empirical channel data from IoT devices equipped with a tripolar antenna, we show that the proposed Max-Sum and Max-Min schemes reduce antenna switching by over 80%, when compared to selection diversity. In addition, these two approaches lead to a median gain of 1.8 and 0.3 dB and a 1% diversity gain of 3.6 and 1.4 dB, respectively, relative to switched diversity.

A Bandwidth-Enhanced Tunable Decoupling Method for Compact Mobile Terminal Antennas

This article presents a tunable decoupling method for closely spaced multielement antenna systems, which is able to enhance the decoupling bandwidth of each tuning state. The decoupling method utilizes parasitic scatterers and tunable circuit components, and its design approach is systematically studied. The decoupling method is evaluated by performing a simulation in which the decoupling bandwidth in a tuned state for a three-element antenna system is examined. In that case, only the circuit components are optimized. As another example of this procedure, the frequency reconfigurable decoupling bandwidth for a two-element antenna system is shown to increase by optimizing the parasitic scatterer and the circuit components in the lossless and realistic cases. This study is concluded by presenting a realistic evaluation for the decoupling of a two-element antenna in different tuned states.

Design of Wideband Decoupling Networks for MIMO Antennas Based on an N-Ary Optimization Algorithm

Techniques for reducing the coupling between antenna elements in multiple-input multiple-output (MIMO) systems are important for achieving the full potential of MIMO. In this article, a general and systematic method is developed to design a wideband decoupling and matching network (DMN) for MIMO antenna arrays. The DMN is formed by grid-like transmission lines interconnected by lumped components, whose reactances can be obtained from an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N-</i> ary optimization algorithm. Four design benchmarks are performed for validating decoupling methodology, elaborating on design/implementation procedure, and demonstrating superiority of the proposed method. Results show that the DMN achieves broad isolation bandwidth while occupying a small footprint area. Besides, the DMN is applicable for symmetric, asymmetric, and multi-element MIMO antenna arrays. In comparison to prior works, the proposed DMN offers a wider isolation bandwidth, higher efficiency, and comparable size.