Four-element Array Research Articles

A Wideband and Compact Millimeter-Wave Antenna Array Fed by Printed Ridge Gap Waveguide for 5G Applications

This paper proposes a printed ridge gap waveguide (PRGW)-based 2 × 2 millimeter-wave antenna array with broad bandwidth and compact aperture. A dual-resonance element consisting of a quarter circular and a quarter annular patch is initially designed. Subsequently, to reduce the cross polarization (XP) radiation and enhance the gain of the proposed antenna, a four-element array with symmetric arrangement is developed, leading to a decline in the normalized XP levels from -4.5 to -18.9 dB and from -4.4 to -18.7 dB in the xoz and yoz planes, respectively. In addition, a pair of parasitic shorted half-circular patches is loaded to improve the antenna gain in the highfrequency range. Finally, a PRGW feeding network is designed and applied to provide differential feeding for the planar array. To validate the reflection and radiation performance, an array prototype is fabricated, and experimental verification is conducted. Measurement results show that a -10-dB impedance bandwidth of 14.3% (26.0–30.0 GHz) is realized for the prototype, and an average realized gain of 9.8 dBi with low XP radiation is achieved by the proposed array.

A High-Precision, Ultra-Short Baseline Positioning Method for Full Sea Depth

To fulfill the demand for high-precision underwater acoustic positioning at full sea depth, an ultra-short baseline (USBL) positioning method with the square array based on the least squares estimating signal parameters via rotational invariance techniques (LS-ESPRIT) algorithm is presented in this paper. A combination of beam tracking and beamforming is employed to improve the accuracy of direction-of-arrival (DOA) estimation and, consequently, enhance overall positioning accuracy. In order to mitigate the issue of position jumping resulting from phase ambiguity in traditional four-element cross arrays, we have improved the stability of the positioning algorithm by utilizing a multi-element square array and employing the LS-ESPRIT algorithm for DOA estimation. Furthermore, the signal detection method integrating the correlation coefficient and ascending/descending chirp signals is employed to enhance the reliability of the location algorithm. Simulation analysis and experimental results demonstrate that the proposed algorithm effectively enhances positioning accuracy and improves the problem of jumping in positioning results.

Using a metasurface to enhance the radiation efficiency of subterahertz antennas printed on thick substrates

This study investigates the possibility of increasing the radiation efficiency of printed antennas and arrays by suppressing their inherent surface waves using a metasurface made of quad-split rings (QSR). A symmetrical resonant microstrip dipole and a four-element series-fed dipole array printed on an infinite grounded dielectric layer (layer thickness: 0.2 mm; relative permittivity: 9.4; tanδ: 0.0005) were simulated with FEKO 2022 software. Conducted at 100–116 GHz, the numerical results revealed extremely low radiation efficiencies of approximately 31% and 40% for the studied dipole and dipole array, respectively, which resulted from the presence of surface waves in the dielectric. However, placing only one QSR near each dipole arm triggered an increase in radiation efficiency by 2.5 times (up to 75%). The use of a metasurface in the form of two small QSR arrays triggered a pronounced improvement in radiation efficiency, reaching 93.6% and 95.8% for the studied dipole and dipole array, respectively. Analysis of the electric field distribution images showed that this enhancement resulted from surface wave suppression.

Compensation of high-power interference using eigen vectors of the correlation matrix

Formulation of the problem. The main means of protecting the navigation equipment of consumers of the global navigation satellite system from intentional interference is the spatial selection of information signals using an adaptive antenna array. In this case, the weight coefficients of the antenna array must be calculated without using information about the directions to the signal and interference sources. To calculate the weighting coefficients, the eigenvectors of the correlation matrix of the input signals of the antenna array, obtained during its spectral decomposition, can be used. Purpose. The purpose of this work is to present an algorithm for spatial interference compensation based on the spectral decomposition of the correlation matrix of the input signals of an adaptive antenna array and to evaluate its effectiveness. Results. An algorithm for spatial compensation of interference in a four-element adaptive antenna array is presented, based on the spectral decomposition of the correlation matrix of its input signals. The effectiveness of the presented algorithm was assessed using computer simulation. It was found that when the input of the antenna array was exposed to three interferences with an amplitude 500-2000 times greater than the amplitude of the information signal, the level of interference at the output of the antenna array decreased by more than 4000 times. Practical significance. The results obtained can be used in the development of a compensator for interference signals of navigation equipment of consumers of the global navigation satellite system.

Optical integrated reconfigurable mode generator-multiplexer for radio-frequency orbital angular momentum.

Radio-frequency orbital angular momentum (RF-OAM) mode multiplexing has received increasing attention in next-generation (6G) wireless communication as a new spatial multiplexing dimension to further extend data capacity. In particular, the circular antenna array (CAA) based RF-OAM generation using photonic methods is a promising approach due to its flexible reconfigurability, low propagation loss, high operating bandwidth, and high pattern quality. However, most current reports focus either on the bulk optics-based implementations or on band-limited delay line-based approaches. In this paper, we present a novel phased array-based integrated photonic RF-OAM generator-multiplexer for a four-antenna CAA system supporting three RF-OAM modes at 16 GHz for both fast mode switching and mode multiplexing. It consists of a specially designed interleaved optical filter and a four-element phased array based on cascaded phase shifters. By changing the pair of wavelengths used, the output RF-OAM modes can be quickly switched between fundamental mode and ±1 modes. A bandwidth of 1 GHz was experimentally demonstrated. Mode multiplexing can be achieved when all three wavelength pairs are loaded.

The use of a low-cost, small-aperture array as an auxiliary tool to improve infrasound monitoring in the Azores region

AbstractThe 2022’s seismo-volcanic crisis on São Jorge Island of the Azores archipelago has provided an opportunity to deploy a portable infrasound array as a collaborative work between the Research Institute for Volcanology and Risk Assessment (IVAR) of the University of the Azores (UAc) and the University of Florence (UniFI). The four-element array, SJ1, became operational on 2 April 2022. Despite being deployed in a first stage to monitor the activities related to the volcanic unrest on São Jorge Island, SJ1 worked as a supporting tool to the existing IMS infrasound station IS42, located on Graciosa Island at ~ 40 km distance, leading to an enhancement of the infrasonic monitoring network in the region. This work emphasises the importance of low-cost portable infrasound arrays to improve the coverage of infrasound observations for local and regional monitoring purposes in the Azores region. Two events recorded by both arrays are briefly exemplified: a low-magnitude earthquake on São Jorge Island and a fireball which crossed the North Atlantic Ocean. Infrasound data from both arrays are combined to obtain a fast but still accurate source localization of the analysed events.

Design of Microstrip Antenna Arrays with Rotated Elements Using Wilkinson Power Dividers for 5 G Customer Premise Equipment Applications

Microstrip antenna arrays are proposed in this paper for the customer premise equipment (CPE) applications in the frequency range 1 (FR1) of the 5th generation (5 G) mobile networks. The proposed antenna arrays consist of three FR4 substrates. Antenna elements and feeding networks are optimized separately through parameter studies and then combined to form the proposed antenna arrays. Bandwidth-enhancing parasitic elements on the top substrate are broadside coupled to the microstrip antennas in the middle substrate, which are probe-fed by the microstrip feeding network using Wilkinson power dividers realized in the bottom substrate through the ground plane and the stud supporting air layer between the lower two substrates. Two antenna arrays, with four and eight antenna elements, are proposed for different gain specifications, 10 dBi and 12 dBi, respectively. Bandwidths of 10-dB return loss for both arrays fully covered the 5 G n78 frequency band (3.3–3.8 GHz). 20 dB isolation between antenna elements can also be achieved using the proposed layouts with rotated elements. The dimensions, radiation gain, and efficiency of the proposed antenna units, four-element array, and eight-element array are 65 × 65 × 11.4, 115 × 115 × 11.4, and 115 × 215 × 11.4 mm3, 6.2, 10.5, and 13 dBi, 74%, 56%, and 50%, respectively. The proposed antenna arrays exhibit the advantages of simple, low-cost, low-profile, and high-gain characteristics, which is potentially applicable to 5 G CPE outdoor unit (ODU)-related devices.

Dual-Band Millimeter-Wave MIMO Antennas For 5G Wireless Implementation

For 5G wireless applications, this exploration proposes a dual-band 28/38 GHz 4-component MIMO array depending on duplex-mode planar monopole antennas. Four planar monopole antennas are part of the layout framework, situated at the districts of a Rogers RO4003 substrate measuring 20 by 20 mm2 and with a dielectric constant of 3.55. The form of the suggested placoid monopole antenna is crescent-shaped. We created a notch at the bottom and inscribed two rectangular holes on each side to get the required behaviour and execution. For enhancement of isolation, we also employed a limited ground plane. Antenna elements can achieve significant isolation (> − 23 dB) using spatial and scattering behaviour approaches. A illustration of the four-element MIMO array is created, manufactured, and measured to multifariousness the outline idea. The investigational outcomes demonstrate that the suggested antenna has strong isolation and high efficiency while covering the 27.25–29 GHz and 34.5–41 GHz bands. Additionally, studies are done on the channel capacity, realized gain, and radiation pattern. The obtained findings suggest that, for millimeter-wave 5G MIMO implementation, the proposed MIMO antenna might be an excellent application-oriented design.

Design and Simulation of a High Performance 5G mm-Wave MIMO Antenna Array for Mobile Applications

This paper presents the design and simulation of an efficient multiple input multiple output (MIMO) antenna array for 5G millimeter-wave (mm-wave) mobile applications. With a dielectric constant of 2.2 and a loss tangent of 0.0009, the substrate employed is a Rogers RT5880 that is 0.254 mm thick. The 37 GHz frequency spectrum, reserved for millimeter-wave mobile applications for 5G, is covered by the proposed MIMO antenna arrays. The single antenna element has a gain of 6.44 dBi, which is increased to 7.89 dBi with a two-element array configuration and 10.88 dBi with a four-element array configuration. The proposed MIMO antenna array performance metrics—including reflection coefficient, VSWR, radiation efficiency, and gain—are seen and discovered to be below the accepted threshold. In the desired operating frequency band, it is noticed that more than 85% of the proposed MIMO antenna array's radiation efficiency is achieved. According to simulation findings, the proposed design may be potentially feasible for mobile applications using millimeter waves in the 5G network.

A Novel Wideband Splitter for a Four-Element Antenna Array

In the paper, a novel design of a wideband power splitter for a four-element antenna array using two RF antiphase segments is proposed. Based on a detailed analysis of the power splitter circuit, an analytical model was set up in the MATLAB environment. The derived analytical model allows the development of a design of the described structure for any operating frequency and estimates the properties of the designed structure. In addition to the RF electrical part, the copper cover is also considered in this study. The copper cover serves as both a support and shielding part of the proposed structure. The electrical part consists of two sections of transmission lines. The first transmission line is symmetrical, while the second transmission line is asymmetrical. The given transmission lines can be realized using any technology (microstrip, coaxial, etc.). A prototype of the proposed wideband splitter operating at 650 MHz with a fractional bandwidth of 84.3% was designed and tested in real-world conditions to prove the concept. The board of the manufactured prototype has dimensions of 25 × 152 mm. A double-sided FR4 material with a substrate height of 1.48 mm, copper thickness of 50μm, and ϵr ≅ 4.3, with a dielectric loss tangent of 0.021 was used to manufacture the prototype. The prototype was tested and its parameters were verified in practical conditions as a part of the current radio communication system for the 5G band. Under these conditions, verification measurements of the proposed splitter with a four-element antenna array were carried out.

Photoluminescence-Electrochemiluminescence Dual-Mode Sensor Arrays for Histidine and Its Metabolite Discrimination and Disease Identification.

Histidine (His) and its metabolite analysis is significant due to their vital roles in the diagnosis of diseases. In practical applications, simple and effective detection and discrimination of these metabolic species are still a great challenge due to their highly similar structures. Herein, photoluminescence (PL)-electrochemiluminescence (ECL) dual-mode sensor arrays consisting of a series of sensing elements were proposed for simultaneous quantitation and accurate discrimination of His and its four key metabolites (including histamine, imidazole-4-acetic acid, N-acetylhistamine, and imidazole propionate). The sensing elements of these sensor arrays were constructed by employing two solvent iridium(III) complexes ([Ir(pbz)2(DMSO)Cl] and [Ir(ppy)2(DMSO)Cl], pbz = 3-(2-pyridyl)benzoic acid, ppy = 2-phenylpyridine) with excellent PL and ECL performances as cross-responsive sensing units. Based on diverse coordination abilities of the two complexes with the imidazole group of the five targets, PL and ECL responses of each sensing unit can be enhanced to various degrees, which generate unique fingerprint patterns for the corresponding targets. Through principal component analysis, the multifarious patterns (two-, three-, and four-element sensor arrays) can be transformed into simple visualization modes, from which His and its four key metabolites can be effectively discriminated against each other. Moreover, the quantitation of an individual metabolic species at different concentrations and the recognition of the mixtures with different ratios were also accurately achieved. Notably, His and its four key metabolites in urine can also be successfully discriminated by the as-fabricated sensor arrays, and the patients with kidney diseases can be identified clearly, providing a promising way for disease diagnosis.

A curious case of monsoon low frequency reverberations from the mighty Himalayas

This paper presents an investigation of monsoon-generated infrasound events recorded in Islamabad, Pakistan. The majority of these events originate from a specific azimuth band, pointing towards the Himalaya mountain range in the Indian subcontinent. Although the monsoon phenomenon is well-known to develop over the Bay of Bengal and the Arabian sea and enters Pakistan along the foothills of Himalayas and south-eastern areas of Sindh, Pakistan, the associated infrasound signals have a distinct frequency signature that differs from mountain-associated waves (MAW) and microbaroms. While MAW have a frequency of 0.015–0.1 Hz and microbaroms are found in the frequency band 0.13–0.35 Hz, the monsoon-associated signal is mostly observed in the frequency band 0.6–1.1 Hz. This research highlights the potential of studying monsoon-generated infrasound events as an unexplored area of research in the study of the atmosphere and an important weather phenomenon. The paper also reports a strong correlation between these events and rainfall precipitation, which could potentially benefit early weather warning systems, especially in the context of climate change. The MATLAB-based analysis tool, MatSeis, is used for the detection of infrasound events, and the data collected from a four-element seismic acoustic array with Chaparral Physics 50A sensors in Islamabad are analyzed from June to September in the years 2021 to 2022. Overall, this study highlights the significance of monitoring and analyzing monsoon-generated infrasound events in the region.

Design Optimization of Feeding Networks with a Special Size for Self-Interference Cancellation

This letter introduces an effective self-interference cancellation (SIC) for improving isolation between transmit (Tx) ports and receive (Rx) ports of an in-band full-duplex antenna with feeding networks (FNs). A significant isolation improvement is realized by replacing the traditional FNs of the antenna with SICFNs. The coupling between Tx and Rx ports is canceled in the FNs due to the specific power ratios and phase difference. Though a Python optimization procedure, the optimal values of the key parameters of the SIC FNs can be determined. To validate the proposed SIC technique, the prototype consisting of two four-element antenna arrays and four SICFNs designed with the technique is fabricated. The results of measurements performed in an anechoic chamber show an isolation improvement of 15 dB at 3.6 GHz, while only 0.3 dB gain loss for the antenna array as a sacrifice is observed.

A Two-Stage Beamforming Antenna Using Butler Matrix and Reconfigurable Frequency Selective Surface for Wide Angle Beam Tilting

A two-stage beam-forming technique for a wide tilt angle is proposed in this letter. The proposed structure has the potential to overcome the limitations of Butler matrix-based beam-forming technique and reconfigurable FSS-based beam-forming technique, both of which normally lag behind in the present generation of wireless communication due to lesser number of radiating beams. The composite system comprises three parts: a 4 × 4 Butler matrix, an antenna array of 1 × 4 elements, and a reconfigurable FSS layer. Four semi-rigid coaxial cables are employed to connect the Butler matrix to the four-element antenna array. The reconfigurable FSS is mounted on top of antenna layer using air spacers. The FSS superstrate layer consists of 6 × 6 reconfigurable unit cells, which have been further divided into two equal sections to increase the number of radiating beams. Combining the four-port Butler matrix with reconfigurable FSS allows the system to generate twelve unique radiating beams in twelve distinct directions in three-dimensional space. The proposed system is designed, fabricated, and measured for operating frequency of 5.5 GHz. The proposed system attains a maximum tilt of 72° and peak gain of 11.8 dBi.

Energy partitioning of the underwater soundscape

A four-element three-dimensional hydrophone array has been deployed on the Strait of Georgia node of the Victoria Experimental Network Under the Sea (VENUS) since March 2020. To the present, continuous pressure time series data from the four sensors has been streamed ashore and made available by Ocean Networks Canada. A technique for classifying and partitioning ambient noise using the three-dimensional noise coherence function is applied to the recordings. The noise coherence (directionality) due to wind generated surface noise and individual ships is analytically modelled using measured environmental inputs such as the time varying sound speed profile and sediment properties from the measurement site and compared with the observation. The theoretical coherence curve is computed by mixing the contributing sources until a best-fit is found. Since the wind generated surface noise coherence is stable and independent of the source effective sound power per unit area, the contribution of ship noise to the soundscape can be exactly determined. Applying this algorithm to the long-term data set allows the relative contribution of ship noise to the soundscape in the region to summarized succinctly. [Research supported by ONR.]

Broadband Dual-Polarized Phased Array With Dynamic Scanning Control for Intelligent Mobile Communication Application

This work investigates a low-cost, broadband, dual-polarized, beamwidth reconfigurable phased array for dynamic beam-scanning control. Both the beamwidth in the E-plane and H-plane are synchronously extended by introducing the vertically polarized (VP) field components. Then, by exploring a switch-loaded omnidirectional source, a novel dual-polarized wide/narrow beamwidth switchable or reconfigurable method is proposed. To meet the demand for intelligent mobile communication for dynamic beam steering, the dual-polarized beamwidth reconfigurable radiator as the array element is used for the phased array or MIMO designs. As a proof of concept, an interesting four-element reconfigurable dual-polarized phased array is implemented in the Sub-6 GHz band. By controlling the switch states of each element, this array can be operated in two modes: <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">wide-angle scanning coverage (V2V connection) and long-distance high-gain scanning (V2I communication)</i> . In wide-angle scanning mode, the main lobe of the array can scan from -60° to +55°, and its peak gain is 9.1 dBi. In long-distance high-gain scanning, this array can scan the beam in the range of [-35°, +35°] with a peak gain of 11.2 dBi. Besides, the isolation between different elements or polarization is greater than 13 dB. This reconfigurable phased array demonstrates the advantages of low-cost, broadband, and flexible beam-steering capability. It is expected to find broad applications in intelligent vehicular communication and low-cost phased array.

Linear phased meta-material incorporated patch antenna array at sub-6 GHz for 5G base stations

ABSTRACT This article presented a four-element dual-band linear phased antenna array operating at sub-6 GHz. The single-element antenna was designed by mounting a double-negative single- layered Complementary Split Ring Resonator (SL-CSRR) on the patch and grounding with a rectangular slot and four SL-CSRR’s array; it was resonated at dual bands 3.43–3.56 GHz and 4.93–5.75 GHz and got size shrinkage of 80.45% with dimensions 0.35λx0.35λx0.028λ mm3. The proposed phased array antenna was resonated in 3.42–3.57 GHz and 4.86–5.74 GHz with central frequencies 3.49 GHz and 5.18 GHz, respectively, with respect to −10 dB impedance bandwidth. It was dimensioned with 0.35λx2.42λx0.028λ mm3. The isolation of > 16 dB, ECC < 0.1, DG ~ 10 dB, CCL < 0.15bits/s/Hz and MEG<-6 dB were achieved. The maximum gain of 8.4dBi and 10.4dBi and maximum efficiency of 81.14%, and 99.12% were achieved over the two resonated bands, respectively. The array antenna excited initially with 0° phase difference was radiated bi-directional beam focused to 0° and 180° in the pattern like a broadside array and with the change of phase difference, the structure capable to focus the beam to ± 90° like end-fire array at 3.49 GHz and it was capable to steer the beam to ± 48.6° at 5.18 GHz. These results demonstrated that the proposed phased array antenna is a good candidate to provide services at base stations for 5 G sub-6 GHz applications. The prototypes of the single-element antenna and four-element phased array antennae were fabricated and tested. The matching of simulation results with measurement one has a good commitment to similarity.

Compact Millimeter-Wave Array With Wide-Angle Scanning for Mobile Phones

This paper describes a compact four-element wide-angle scanning millimeter-wave array for mobile phones. The wide-angle scanning array with four elements is achieved with a small element spacing of 0.3λ0. Two critical difficulties for the compact array with 0.3λ0 spacing are the realization of the small element and the mutual coupling reduction between each element. For the small antenna element, a modified quarter-wavelength shorted patch antenna element working at the 25.5-27.5 GHz is designed. The coupled shorted structure and coupled feeding structure of the element is designed to reduce the H-plane cross-polarization level (XPL) which is a key drawback of quarter-wavelength shorted patch antenna. For the mutual coupling of the four-element array with 0.3λ0 spacing, three compact neutralization lines (NLs) are applied to reduce the mutual coupling to better than -15 dB. Finally, the proposed compact four-element array only occupies a small size of 1.14λ0 × 0.3λ0, which is the smallest mm-wave four-element array in the open literature. Also, the proposed array can scan from -60° to 60° with a peak gain of 9 dBi, a gain fluctuation less than 1.3 dB, a good sidelobe level, and an acceptable cross-polarization level. The proposed mm-wave array with the superior performance of a small array size and wide beam scanning is promising for modern mobile phones.

Investigation of Planar Isolators for Mutual Coupling Reduction in Two-Dimensional Microstrip Antenna Arrays

The design of isolators to reduce mutual coupling in large two-dimensional antenna arrays is complex and requires significant computational effort. This work attempts to alleviate this problem by applying different types of planar isolators in different orientations and experimenting first with two-element microstrip antenna arrays. A U-shaped planar transmission line isolator, a U-shaped planar transmission line-based destructive ground structure, and a planar neutralization line structure are designed to reduce E-plane or H-plane coupling in two-element microstrip antenna arrays. A mutual coupling reduction of approximately 6 dB is achieved. Four combinations of these planar isolators are compared and analyzed in a four-element microstrip antenna array. An optimal combination is then obtained by using two reversely placed U-shaped line isolators, which reduce the mutual coupling by more than 6.1 dB. The study is also extended to a 5 × 5 antenna array. Similar results of mutual coupling reduction are obtained. In addition to simulation, both two-element and 25-element microstrip antennas have been constructed and tested. The agreement of the simulation results with the measured results confirms the effectiveness of the decoupling structures.

Evaluation of the noise immunity of the navigation equipment of consumers of the global navigation satellite system with spatial adaptation based on the algorithm of maintaining the level of the useful signal

Problem statement. The use of spatial filtering of signals in adaptive antenna arrays (AAR) of consumer navigation equipment (NAP) of the global navigation satellite system (GNSS) in conditions of intentional interference is an effective means of ensuring stability and continuity of positioning of mobile objects. The specifics of solving this problem is the low level of navigation signals received from the upper hemisphere of space against the background of powerful concentrated interference, significantly exceeding noise. Most compact L-band AARs consist of 4-8 elements, and the algorithms used optimize compensation indicators without the presence of a priori information about the position of useful and interfering signals. At the same time, the formed dips on the sources of interference in width can lead to a loss of the availability of spacecraft signals for subsequent processing. This circumstance determines the relevance and practical orientation of the task of evaluating the effectiveness of the diagram formation algorithm, taking into account the integration of interference attenuation indicators and maintaining the level of the useful signal. Purpose. Investigation of the characteristics of the spatial interference compensation algorithm with a linear restriction on the direction of reception of the useful signal, as well as an assessment of its impact on the performance of the equipment of consumers of the global navigation satellite system. Results. The level of compensation of spatially distributed interference sources is analyzed using a processing algorithm that minimizes the average power of the adaptive antenna array with the exception of the direction of reception of the useful signal to the zenith. The influence of the spatial compensator on the availability of spacecraft signals for subsequent processing, depending on the number, level and angular coordinates of interference sources, is investigated. Practical significance. A model is proposed for evaluating an algorithm that maintains constant gain at the zenith and minima in the interference directions for a four-element L-band antenna array. The given values of interference attenuation depending on the number, level, angle of location and azimuth of the impact make it possible to clarify the indicators of noise immunity of the equipment of consumers of a global navigation satellite system equipped with a spatial compensator.