Four-element Antenna Array Research Articles

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.

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.

Low-cost thin film patch antennas and antenna arrays with various background wall materials for indoor wireless communications

The present study introduces an inkjet-printed flexible coplanar waveguide patch antenna array concept. Single antenna and four-element antenna arrays were characterized, which were attached to a subminiature version A connector via an innovative solderless, 3D-printed ‘plug-and-play-type’ tightener. Furthermore, indoor wireless communication and Internet of Things scenarios with commonly used wall materials including gypsum and plywood boards, on which patch antennas and antenna arrays can be attached, were also presented. In order to validate the concept, design and fabrication iterations in parallel with numerical and experimental investigations were executed. To elaborate, single antenna and antenna array configurations without and with wall materials were characterized to see their functionality at 2.4 GHz resonance frequency and beyond 300 MHz bandwidth, respectively. The results demonstrate that the investigated configurations fulfill short-range radio transmission and can be utilized, e.g., for indoor backscattering-type communications and wireless sensing applications, as an affordable and versatile alternative to their conventional counterparts. Being attached to their corresponding background materials, single-antenna specimens were measured to have return losses beyond 18 dB and peak gains around 1 dBi, while higher peak gains above 6 dBi were detected for antenna arrays. Moreover, the antenna arrays can enable multiple-input and multiple-output communication. The proposed arrays had diversity performance in terms of return losses higher than 15 dB, isolation of more than 20 dB, envelope correlation coefficient , diversity gain dB, mean effective gain dB, power ratio factor dB, and channel capacity loss bits/s/Hz.

A left hand circularly polarized (LHCP) wideband antenna array based on artificial magnetic conductor for Ka-band applications

A left-hand circularly polarized (LHCP) 2 × 2 array antenna is presented based on a modified artificial magnetic conductor (AMC) with improved gain and side lobe levels (SLLs). A single port modified sequentially rotated feed network combines the four corner truncated patch elements to achieve wider impedance bandwidth and axial ratio (A.R) bandwidth. The AMC array having wideband behavior consists of 9 × 9 unit cells with a single unit cell size of 2.4 × 2.4 mm2. The particular AMC-surrounded antenna array is simulated and manufactured using Rogers RT Duroid/5880 substrate and provides a wider bandwidth covering Ka-band (27 GHz to 32 GHz). The dimensions of the AMC integrated antenna array are 30 × 30 × 0.508 mm3. The proposed AMC shows in-phase reflection behaviors between (+ 90 and − 90) degree, from 27 GHz to 32 GHz. Combining the four-element antenna array with the AMC reflector improved the gain level of 0.7 dBi, 2.9 dBi, and 2.5 dBi at 28 GHz, 29 GHz, and 30 GHz, respectively. The simulated s-parameter (S11) and radiation patterns results are experimentally verified by measuring the prototype of the recommended antenna model. The proposed antenna array shows a stable gain variation and directive radiation patterns along 0o with low side lobe levels. Based on the performance, the proposed AMC-based antenna array can be an effective choice for the 3 U satellite applications in Ka-band.

A hemispherical helical water antenna array for directional high-gain radiation

This letter proposed a water antenna with a novel shape of a hemispherical helix made of pure water. A plastic water pipe is bent into a hemispherical helix and filled with water to form the helical arm of the antenna. The water arm acts as a director, which enables the antenna to obtain wide-angle radiation characteristic in the axial direction with a beam width of 95.5°. The impedance bandwidth of the antenna (S11 < −10 dB) is 1.30–1.89 GHz. Based on this antenna, a four-element antenna array is also designed. A quasi-Butler matrix is used to feed this antenna array to achieve a reconfigurable pattern. The antenna array can achieve directional high-gain radiation in five directions, covering a total range of 66°. The maximum gain of the array in the effective frequency band can reach 13.8 dBi.

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.

A broadband single-layer substrate integrated waveguide cavity-backed slot array antenna with improved gain

ABSTRACT A single-layer substrate-integrated waveguide (SIW) cavity-backed slot array antenna with broad impedance bandwidth and improved gain is presented in this paper. In the element design, a multi-branch slot and a pair of inclined slots are designed on the top layer of the SIW as radiating structure and the grounded coplanar waveguide feeding structure are used for impedance matching, which ensures that the triple special resonant modes with the odd TE120 mode, the half TE120 mode, and a hybrid mode can be excited successfully to obtain broad impedance bandwidth and high gain, because of its low order and adjacent working frequencies points. Following this, an array antenna consisting of four elements and a four-way microstrip feeding network using only single-layer substrate structure is simulated and fabricated. The measured impedance bandwidth of the four-element array antenna achieves up to 34.4% and the measure peak gain at desired frequency band is 14.4 dBi with an aperture efficiency of 71.1%. The measured results prove that the proposed design has advantages of simple structure, broadband, and high gain, which is expected to be applied in high-speed vehicular communication system.

Designed A Broadcast Patch Antenna

Today, one of the key topics of study in the field of communication systems is wireless technology, and no studies of communication systems is complete without a grasp of how antennas work and are made. Numerous scholars have investigated antennas for various wireless communication systems. The conceived, created, and tested omnidirectional microstrip patch antenna (MPA) is the subject of this study. The antenna's operational bandwidth is a good fit for a variety of applications. Microstrip patch antennas are the ideal option for communication systems engineers due to its effectiveness and advantages, which include low cost, low profile, and low weight. Due to the fact that they may combine with microwave circuits, they are ideal for applications like cell devices, many others, including WLAN applications and navigational systems. In this project, a small rectangular patch antenna is created. The research of a two- or four-element array antenna has been the focus of the work's last section. The optimization of a 1.9GHz rectangular probe fed patch antenna in the design and simulation of patch antennas. According to experimental findings, the voltage standing wave ratio, insertion loss and capacity.

Broadband high gain cavity resonator antenna using planar electromagnetic bandgap (EBG) superstrate

AbstractThis paper presents a broadband miniaturized Fabry–Perot cavity resonator antenna (CRA) made of novel electromagnetic bandgap (EBG) superstrate as partially reflecting surface (PRS) and reactive impedance surface (RIS) backed rectangular patch antenna. To the best of the authors' knowledge, the proposed EBG exhibits the highest stopband bandwidth (BW) with a bandgap existing between 7.37 and 12.4 GHz (50.9%). Frequency-selective property of the EBG is utilized under plane wave incidence to demonstrate it as PRS superstrate in CRA antenna. The cavity is excited with a rectangular microstrip antenna which is made of two dielectric substrates with an additional RIS layer sandwiched between them. The RIS provides wideband impedance matching of the primary feed antenna. A 7 × 7 array of the EBG superstrate is loaded over the patch antenna having an overall lateral dimension of only 45 × 45 mm2 or 1.62 λ0 × 1.62 λ0 where λ0 is the free space wavelength at the center frequency of 10.8 GHz. The proposed Fabry–Perot CRA (FP-CRA) achieves gain enhancement of 6.59 dB as compared with the reference antenna and has a 10 dB return loss BW of 23.79% from 10.07 to 12.79 GHz. A prototype of the FP-CRA is fabricated and experimentally tested with single and dual layers of EBG superstrate. Measured results show BWs of 21.5 and 24.8% for the two cases with peak realized gain of 12.05 and 14.3 dBi, respectively. Later a four-element antenna array with corporate feeding is designed as the primary feed of the CRA. The simulation result shows a flat gain of &gt;13 dBi with gain variation &lt;1.2 dB over the impedance BW of 13.2%.

Design of a Compact High Isolation 4-Element Wideband Patch Antenna Array for GNSS Applications

This work presents a compact (125 mm diameter) wideband four-element antenna array with a high isolation level for Global Navigation Satellite System (GNSS) anti-jamming applications. The array consists of four identical right hand circularly polarized (RHCP) single feed rectangular patch antennas that can cover BeiDou B1 band (1559.05 – 1563.15 MHz), GPS L1 band (1563 – 1587 MHz), Galileo E1 band (1559 – 1591 MHz), and GLONASS G1 band (1593 – 1610 MHz). The proposed array has a wide frequency bandwidth of 100 MHz (1.55 – 1.65 GHz) with an axial ratio of less than 3 dB. The patch antenna elements are designed on a substrate that has a high dielectric constant to achieve a compact size. The size of each patch element is only 32 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times 32\times5.08$ </tex-math></inline-formula> mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . These patches are placed along the circumference of a circular aluminium ground plane of 125 mm diameter and 1.5 mm thickness in a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\times 2$ </tex-math></inline-formula> symmetrical arrangement. The edge-to-edge distance between the opposite patch elements is only 48 mm while for the adjacent elements the separation is only 27 mm. A microwave absorber material is employed to achieve an extremely low mutual coupling level over a wide frequency range (1.55 – 1.65 GHz) within a compact form factor. The proposed design achieves a mutual coupling of less than −20 dB within a compact overall form factor of 125 mm diameter over the entire band of interest. The simulated and measured results of reflection coefficient, mutual coupling, null steering, null depth, and radiation pattern show that the proposed antenna array is an excellent choice for multiband GNSS applications.

Dual Frequency Millimeter-Wave Perturbed Ring Patch Antenna Array for 5G Applications

A dual-band antenna array has been reported in this paper working in the fundamental mode of TM11 resonance for 5G communication. Rogers Rt/Duroid 5880 as dielectric substrate having a height of 0.508 mm has been chosen for the proposed antenna. A single element ring patch antenna has been developed by etching circular slots at different angles i.e. 0°, 90°, and 180° making it perturbed which resonates at 28 GHz providing an impedance bandwidth of 4% by exciting two resonant modes making it novel. Further, to cultivate the gain, a four-element antenna array is evolved by utilizing series-feed network due to which the flux linkage of the radiating element combines with the conductive behaviour of the feed network resulting an extra resonance at 36 GHz providing reflection coefficient of more than –20 dB at both resonating frequencies. By constructing an array, the antenna gain gets doubled along with a 1% increase in impedance bandwidth at 28 GHz. By considering the various electromagnetic parameters, a detailed analysis has been done using CST MW studio ver.2018. Further, to authenticate the result of the reported antenna array, the antenna has been fabricated as well as tested using VNA which shows close resemblance with simulated antenna characteristics.

VHF/UHF Open-Sleeve Dipole Antenna Array for Airborne Ice Sounding and Imaging Radar

This letter presents a simple, lightweight, and ultrawideband, the very high frequency/ultrahigh frequency (VHF/UHF) open-sleeve dipole antenna array for airborne ice measuring radar. The proposed antenna array achieves a wide bandwidth of 300 MHz via mutual coupling from neighboring excited elements. A hollow aluminum tube is used for both dipole and parasitic elements to minimize the antenna's weight. The simulation results show that to achieve a bandwidth of 300 MHz with a peak realized gain up to 12 dBi in the frequency range from 170 to 470 MHz, the length of the dipole (L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dip</sub> ) and parasitic elements (L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">para</sub> ) of elements 1 and 4 of the four-element antenna array need to be 670 mm and 200 mm, respectively. At the same time, elements 2 and 3 require an L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dip</sub> of 640 mm and L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">para</sub> of 180 mm. Based on these dimensions, a four-element antenna array is fabricated and tested. The measured antenna performance results show a good agreement with the simulated results.

24 GHz Flexible Antenna for Doppler Radar-Based Human Vital Signs Monitoring.

Noncontact monitoring of human vital signs has been an emerging research topic in recent years. A key approach to this monitoring is the use of the Doppler radar concept which enables real-time vital signs detection, resulting in a new class of radar system known as bio-radar. The antennas are a key component of any bio-radar module and their designs should meet the common requirements of bio-radar applications such as high radiation directivity and mechanical flexibility. This paper presents the design of a four-element antenna array on a flexible liquid crystal polymer (LCP) substrate of 100 μm thickness and εr of 3.35. The designed antenna array can be used with a 24 GHz bio-radar for vital signs monitoring in a non-contact manner. It features a relatively compact size of 36.5 × 53 mm2 and measured gain of 5.81 dBi. The two vital signs: breathing rate (BR) and heart rate (HR) of two human subjects are detected with relatively good accuracy using the fabricated antenna array and radio frequency (RF) output power of −3 dBm from a distance of approximately 60 cm. The effect of bending on the antenna performance is also analyzed.

Side-Frame Dual-Band MIMO Antennas for 5G Smartphone Applications

A side-frame dual-band multi-input multi-output (MIMO) antenna system for fifth-generation (5G) mobile communication in smartphone applications is presented, operating in 3.5 GHz band (3400-3600 MHz) and 5 GHz band (4800-5000 MHz). The proposed four-element antenna array is placed at four corners of the circuit board and printed on the side edge frame. The height of the structure is only 4.1 mm, which is compatible for ultra-thin full screen smartphones. According to the verification of HFSS and CST, ideal impedance matching bandwidths (superior to 10dB) and excellent isolations (superior to 18 dB) are obtained over the 3.5 GHz band and 5 GHz band, with peak gain of 6.18 dB and 4.9 dB, respectively.

5G dual-band slotted SIW array antenna

A dual-band slotted substrate-integrated waveguide four-element array antenna for the 5G communication system is presented in this manuscript. Two longitudinal slots are responsible for generating frequency bands of 28 and 38 GHz. The proposed antenna is designed on the substrate duroid 5880/Rogers having a loss tangent and dielectric constant of 0.003 and 2.2, respectively. The developed single-element design at 28 GHz provides 6.35 dBi gain, while at 38 GHz it provides 7.3 dBi gain and the simulation is carried out with CST Microwave Studio, 2018. To accomplish high gain, an optimized four-element array antenna is designed with a parallel feeding network on the same substrate that covers 28 GHz (27.6–28.1 GHz) and 38 GHz band (37.9–38.69 GHz). The designed antenna array attains the radiation efficiency of 88.08% with 12.7 dBi gain at 28 GHz and the efficiency of 84.44% with 15.5 dBi gain at 38 GHz band.

Compact Millimeter-Wave Endfire Dual-Polarized Antenna Array for Low-Cost Multibeam Applications

A compact multibeam endfire dual-polarized antenna array for low-cost millimeter-wave (mmWave) applications is proposed in this letter. Multimode substrate-integrated waveguide (SIW) section with interactions is applied as the basic beamformer. The dual-mode SIW is used in the beamforming network to support dual-polarization application without occupying an extra area. The printed dipole antenna with integrated balun and the open-ended SIW antenna with metallic strips are integrated to realize an endfire dual-polarized antenna element. Based on this endfire antenna element, a multibeam dual-polarized antenna array is developed. The proposed antenna array includes a four-element antenna array, an SIW beamforming network, and transitions. Additional air gaps between antenna elements are designed for mutual coupling reduction. The fabricated multibeam endfire dual-polarized antenna array achieves an impedance bandwidth of 11.3%, and the overlapped 3 dB beamwidth of the four generated beams in two polarizations are able to cover a wide range between ± 41°. The proposed low-cost multibeam antenna array can be a good candidate for 5G mmWave wireless applications.

Design of a Four-Element Array Antenna for 5G Cellular Wireless Networks

This paper proposes the design of a four-element array planar antenna based on a single antenna that combines the Double Positive (DPS) and Epsilon Negative (ENG) materials. The single antenna consists of a microstrip segment (which is equivalent to a DPS material) connected to a grounded microstrip segment (which is equivalent to an ENG material). T-Junction power dividers with one-input and two-output ports are used for feeding the two-element and the four-element array antennas. The proposed array antenna is designed to operate optimally at 30GHz frequency under Finite Element Method (FEM)-based simulation. The obtained simulation results show that the proposed array antennas have good radiation performances, in which the four-element array antenna has a -10dB bandwidth ranging from 28.7 to 33.4GHz and 12.9dBi gain.

A 0.7–5.7 GHz Reconfigurable MIMO Receiver Architecture for Analog Spatial Notch Filtering Using Orthogonal Beamforming

A highly reconfigurable direct-conversion software-defined multiple-input multiple-output (MIMO) receiver with four RF inputs and four I/Q baseband outputs is proposed. It allows for digital MIMO but also analog interference rejection by spatial notch filtering through four flexible and simultaneous orthogonal beams. A segmented constant-Gm vector modulator (VM) with improved interference tolerance and wide RF frequency range targeting the sub-6-GHz bands is proposed. It exploits current-domain beamforming before $I$ – $V$ conversion by transimpedance amplifiers. A 0.7–5.7-GHz 22-nm fully depleted silicon-on-insulator (FD-SOI) prototype chip achieves >29 dB spatial filtering for a single notch and an ultrawideband 20-dB notch suppression bandwidth of 2.3 GHz at broadside excitation at an local oscillator (LO) frequency of 2.5 GHz. In the notches, an IIP3 of +16 dBm and B1dB of −11.5 dBm at a 41-dB gain is achieved, improving IIP3 and B1dB by 35 and 27 dB, respectively, by spatial filtering. A single-element noise figure (NF) of 5.5–7 dB is achieved on the VM constellation corners, degrading about 2 dB on the points nearby the biggest circle fitting into a square constellation. However, sub-3-dB system NF is potentially achievable, taking into account up to 6-dB improvement by the four-element beamforming. Given both gain and phase control provided by the VM, spatial patterns with up to three independent nulls can be synthesized with the four-element antenna array. The chip of 0.52 mm2 active area consumes 77–139 mW at an LO-frequency of 0.7–5.7 GHz from a 0.8-V supply.

Package-Integrated, Wideband Power Dividing Networks and Antenna Arrays for 28-GHz 5G New Radio Bands

Package-integrated and ultrathin power dividers with footprint smaller than unit $\lambda ~_{0}~^{\mathrm{ 2}}$ at the operating frequency of 28-GHz 5G new radio (NR) n257 and n258 bands are presented for the first time for small-cell applications. These power dividers are also configured as antenna arrays using endfire Yagi–Uda antenna elements. Utilizing minimal matching techniques, two-, three-, and four-element antenna arrays are designed without compromising on the bandwidth of operation or electrical performance. These thin-film power dividers exhibit a cross-sectional height of $147~\mu \text{m}$ and can be implemented in the top metal layer of front-end module packages. Panel-compatible semiadditive patterning (SAP) process is utilized to realize these structures, which yields precise line space dimensions required for millimeter-wave (mm-wave) applications. This results in power dividers with low added insertion loss, low VSWR, and minimal phase difference between output ports. The added insertion loss is 25% less than similar structures reported on integrated fan-out architectures. The antenna arrays exhibit high gain and efficiency. Excellent model-to-hardware correlation is observed with multiple coupons of the same structure. Package-integrated power dividers and antenna arrays based on ultrathin laminated glass substrate represent a major step toward realizing compact mm-wave antenna-in-package for 5G small-cell applications.