Three-element Antenna Array Research Articles

A Three-Port Coupled Resonator Decoupling Network for Mutual Coupling Reduction of Three-Element Antenna Arrays

A Three-Port Coupled Resonator Decoupling Network for Mutual Coupling Reduction of Three-Element Antenna Arrays

Dual-Band Circular-Polarized Microstrip Antenna for Ultrawideband Positioning in Smartphones With Flexible Liquid Crystal Polymer Process

This article proposes a dual-band circular-polarized (DBCP) microstrip antenna using flexible liquid crystal polymer (LCP) manufacturing process for ON-smartphone ultrawideband (UWB) positioning application. To achieve dual-band circular polarization in a low profile, the proposed antenna is designed with a cross-slot-loaded patch with four L-shaped feeding probes and a sequential phase feeding network. A circle of capacitive via fence is loaded surrounding the patch for area miniaturization, which is adaptive for the limited space of flexible printed circuit (FPC) in smartphones. Based on the UWB positioning protocol, a three-element antenna array is constructed in a low profile of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.015\lambda _{0}$ </tex-math></inline-formula> with required isolation of 17 dB. Experimental results show the overlapped bandwidth of the efficiency and the axial ratio (AR) covering the demand bands of 6.30–6.80 and 7.75–8.10 GHz. With the properties of dual wideband operation, circular polarization, and ultralow profile, the proposed antenna exhibits feasible solutions for the UWB positioning application in space-limited smartphones.

An ultra‐wideband 3 × 3 Butler matrix with unique Vivaldi array structure for high‐range resolution radars

Steerable antenna beam capability is an outstanding expectation for the development of automatic tracking systems and target detection. A switched beam array antenna, which can generate multiple fixed beams with enhanced sensitivity, emerges as a solution for beamforming tracking. On the other hand, it is known that the target can be detected with high-range resolution thanks to ultra-wideband (UWB) systems. In this work, a compact switched beam Vivaldi array antenna based on a Butler matrix for a UWB application capable of target detection with accurate target tracking is presented to meet the high gain and low side lobe level requirements. Based on a three-element antenna array, two methods have been applied to obtain small grating lobes and it has been shown that significant improvements can be achieved. Designed with a 3 × 3 UWB Butler matrix, the UWB array antenna can direct its beams in three directions in a direction range from −42 to 42°. The measured result showed that the group delay was less than about 4.5 ns with variation of less than ±0.7 ns over the entire operating frequency band.

Novel hybrid metamaterial to improve the performance of a beamforming antenna

This paper investigates the design and implementation of a novel hybrid metamaterial unit cell to improve a beamforming Wi-Fi antenna’s performance. The proposed metamaterial unit cell is created on an FR-4 substrate (εγ = 4.4) and a thickness of 1.6 mm. The metallization height of the unit cell is maintained at 0.035 mm. The designed metamaterial unit cell is simulated using HFSS Ver. 18.2 to verify the double negative behaviour. The unit cell consists of five Split Ring Resonators (SRR’s) at the bottom and a hexagonal ring of six triangles. Initially, a conventional inset fed microstrip patch antenna is designed then an array of the proposed unit cell is created and used as a superstrate to study the performance. A Three Element Antenna Array (TEAA) is designed to operate at 2.4 GHz Wi-Fi band, and the superstrate created out of the proposed unit cell is used to study its effect. Metamaterial superstrate improved the conventional Single Element Antenna (SEA) gain by approximately 2 dB. Superstrate with TEAA exhibited an improved gain of 1 dB over TEAA.

Dependence of the arithmetic mean deviation on frequency and on direction of the signal arrival with placement of the three-element antenna array on the unmanned vehicle

Dependence of the arithmetic mean deviation on frequency and on direction of the signal arrival with placement of the three-element antenna array on the unmanned vehicle

Circularly-polarized linear antenna array of non-identical radiating patch elements for WiFi/WLAN applications

Here we present a novel linear circularly polarized (CP) antenna array using non-identical CP elements, where the Chinese character-shaped patches are employed to form a linear array. Namely, the single-feed CP Zhong-, Guo-, and Meng-shaped patch antennas have collected to form a three-element antenna array. A one-to-three power splitter with equal amplitudes but unequal phase-shifts at its output ports was deliberated as the feed network for the linear array. The challenge of this antenna array design is the appropriate phase excitation to the non-identical radiating elements so that the CP gain and operating bandwidth can meet the requirements of the application(s), in which we undertook an in-depth investigation. A proof-of-concept design example for 2.4 GHz wireless local area network (WLAN, IEEE 802.11b/g/n) has demonstrated the effectiveness of the combination technique on the non-identical CP antenna elements. The simulation, in combination with experimental validation, obtained an on-axis 3-dB axial-ratio bandwidth from 2.28 to 2.59 GHz (12.7%), whereas a broadside gain of 9 dBic at 2.5 GHz and an overall efficiency of 82% were recorded within the bandwidth.

Isolation Enhancement for $1\times3$ Closely Spaced E-Plane Patch Antenna Array Using Defect Ground Structure and Metal-Vias

This paper introduces an effective solution for improving isolation in linear antenna array. The array is composed of three-element E-plane single feed patch antennas (the overall size is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.59\,\,\lambda _{0}\,\,\times1.02\,\,\lambda _{0}$ </tex-math></inline-formula> ), which are closely placed with approximately <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.037~\lambda _{0}$ </tex-math></inline-formula> , where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{0}$ </tex-math></inline-formula> is the free-space wavelength at 4 GHz. The decoupling structure consists of T-shaped and rectangular ring shaped defect ground structure (DGS) with six metal-vias. The decoupling mechanism is illustrated by investigating the current vector on the ground plane. The current distribution indicates that the decoupling structure along the outer edge of the radiation patch sever as coupling current converter to produce reverse current opposite to the direction of the ground coupling current, which transmits along the outer edge of the radiation edge. The measured results show that the enhancement in the isolation at 4 GHz is 10.8 dB for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert \text{S}21\vert $ </tex-math></inline-formula> , 17.5 dB for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert \text{S}23\vert $ </tex-math></inline-formula> and 16.6 dB for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert \text{S}31\vert $ </tex-math></inline-formula> . After applying the decoupling structure, the 10-dB impedance bandwidth (3.95 - 4.04 GHz) of antenna 1 remains unchanged. Meanwhile, the 10-dB impedance bandwidth of the antenna, which is located in the middle of the three-element antenna array, increases by 86 MHz (from 114 MHz to 200 MHz). When the decoupling structure is loaded, the maximum gain only decreases by 0.12 dB (from 3.94 to 3.82 dB). The decoupling structure has the advantages of simple structure, easy processing, and independent design of the array, so it can be applied to multielement patch array, such as massive multiple-input multiple-output (M-MIMO) system.

Mathematical Modeling of Multi-Element Antenna Arrays with Chiral Metamaterials Substrates Using Singular Integral Equations

In this paper, a physical model of the multi-element antenna arrays (MEAA) has been considered and a self-consistent numerical method for solving the problem of current distribution on the MEAA surface with chiral metamaterials substrate has been proposed. The algorithm of the input admittance matrix elements for chiral layer based on the conductive left and right-handed helices has been developed and elements of the matrix surface impedances for investigated structures have been found. A set of singular integral equations with a Cauchy kernel for calculating the current density on the surface of the MEAA has been derived. A numerical solution of the set is a well-posed in the sense of Hadamard. Calculations of current distribution on the MEAA surface, impedance characteristics of a three-element antenna array and the dependence of the isolation levels between emitters on the chirality parameter have been performed and analysed. It has been shown that the use of chiral substrates can substantially increase the isolation between emitters.

A Beamwidth Reconfigurable Antenna Array With Triple Dual-Polarized Magneto-Electric Dipole Elements

A novel linearly dual-polarized antenna array with triple elements is proposed for beamwidth reconfigurable base-station communications. By cutting off the arc-shaped corners on the radiated patches, the single dual-polarized antenna unit can obtain a wide bandwidth of 78.4% for SWR ≤ 2, ranging from 1.63 to 3.73 GHz for 2G/3G/LTE and 3.5-GHz C -band (3.4–3.6 GHz) applications. In addition, with the box-shaped reflector and the inherent characteristic of the ME dipole antenna, the average gain of the dual-polarized antenna element is about 11.5 dBi. Finally, by employing a two-stage circuit with several power dividers, a three-element antenna array with a widely adjustable beamwidth in both the $E$ -plane and $H$ -plane is investigated, which could meet the demand of the future smart applications.

Localization of Passive UHF RFID Tags Using the AoAct Transmitter Beamforming Technique

The localization of passive ultra-high frequ- ency (UHF) radio frequency identification (RFID) tags is an emerging technology that has reached a high level of interest in industry and research. Most solutions use classical techniques, such as the angle-of-arrival or the received-signal-strength methods. As an alternative, we present a new approach for estimating the position of a passive UHF RFID tag by using a transmitter beamforming technique that we call angle-of-activation (AoAct). It is based on manipulating the shape of the radiation pattern of the interrogator’s transmitter antenna array. By pivoting the main lobe of the pattern in the azimuth plane of the array and by utilizing the very sensitive response threshold of passive UHF RFID tags, we are able to estimate the tag direction. We use three-channel digital beamforming, where the phases and amplitudes of the antenna array’s feeding radio frequency signals are controlled by the baseband $I$ and $Q$ components of the interrogator’s transmitter signal. Our self-developed hardware pivots the main lobe of a three-element antenna array in a range of ±52° with a resolution of 0.02°. It senses the AoAct with a mean measured accuracy of 1.2° in the anechoic chamber, 1.9° in a basic multipath environment, and 2.5° in a real-world multipath environment. After estimating the AoAct of a tag from different locations, the tag position is triangulated. Experiments show that our AoAct system delivers a localization accuracy of 7 cm in a typical multipath environment.

Fluidic beam steering in parasitically coupled patch antenna arrays

A technique for designing a parasitic patch antenna array whose beam can be steered dynamically using a fluidic tuning mechanism is presented. Using this technique, a three-element patch antenna array operating at 5 GHz is designed and fabricated using 3D printing. Two oil-filled channels are placed in the substrate of the antenna along the radiating edges of the patches and filled with movable metal cylinders and glass balls. The parasitic elements are mutually coupled to the centre element in the H-plane. As the train of metal cylinders and glass balls are moved from the left or right with respect to the centre-driven patch element, the beam is steered towards the opposite direction. The proposed parasitic patch array is able to steer the beam ±22.5° with maintained impedance matching.

Novel Multiport Cavity-Backed Antenna for Low-Cost Array Applications

In this letter, a novel three-element linear cavity- backed antenna (CBA) array with high aperture efficiency is proposed. First, in order to reduce the loss and cost caused by the feeding network, a multiport CBA acting as a radiator as well as a power divider is investigated. Then, based on the multiport CBA, a three-element antenna array with a wide operating frequency band (19-21 GHz) is designed. The simulated broadside gain is from 9.7 to 11.1 dBi over the whole operating band, and the aperture efficiency of the proposed CBA array ranges from 99.1% to 123.7%. The proposed idea has potential applications in low-cost antenna arrays due to the simplified feeding network.

An SDM Method Utilizing Height Pattern Due to Two-Ray Fading Characteristics

A spatial division multiplexing (SDM) transmission method utilizing the characteristics of two-ray fading without relying on narrow beam of the antennas is introduced. This letter formulates the optimized array antenna arrangements and channel capacity as functions of the transmission distance and shows achievable channel capacity for two- and three-element antenna arrays. The letter also describes bandwidth dependency up to 15% bandwidth based on an assumed application to 60-GHz-band gigabit wireless systems. The proposed method provides increased capacity comparable to multiple-input-multiple-output (MIMO) transmission without the extra signal processing cost incurred when using conventional MIMO.

Architecture, Design, and Nonlinear Optimization of Three-Element Biomimetic Antenna Arrays

The architecture, design, and nonlinear optimization process of a three-element biomimetic antenna array (BMAA) are presented and discussed. The array is composed of three λ/4 monopoles with λ/20 spacing. The optimization process is based on choosing the desired phase enhancement factor and output power level of the side elements and maximizing the output power of the center element. A design example in conjunction with numerical simulations and optimization are presented to illustrate the design process and theory of operation of the proposed array. The new array architecture addresses some of the shortcomings of the previously reported two-element BMAAs, and its architecture can be readily extended to arrays with more than three elements.

A Beam-Steering and -Switching Antenna Array Using a Coupled Phase-Locked Loop Array

We present the analysis and experimental results of a beam-steering and -switching antenna array using coupled oscillators and phase-locked loops. With the use of a type-II coupled phase-locked loop array and an external reference signal, the antenna array can steer its beam by a single control voltage, reduce the beam-pointing error arising from the phase errors of the oscillator array, and hold its output frequency stably at the reference signal frequency in operation. Using a double-pole double-throw switch and a difference amplifier at the center element of the antenna array, one can switch the array radiation pattern between the sum pattern and the difference pattern. Moreover, the beam-scanning range is extended to plusmn 90deg by properly using frequency prescalers in the phase-locked loops. The radiation characteristics of a three-element antenna array are measured to verify the array performance.

Miniaturized antenna arrays using decoupling networks with realistic elements

In ordinary antenna arrays, the spacing between radiators is usually chosen lambda/2. In order to use antenna arrays in small mobile platforms, the overall dimensions and, hence, the radiator separation, must be reduced, which aggravates the problem of mutual coupling between radiators. Results are highly distorted beam patterns and greatly reduced radiation efficiency. We propose a method to design a decoupling and matching network for a three-element antenna array with a radiator separation of lambda/10, which additionally allows arbitrary beam patterns assigned to each port-subject to certain constraints. An iterative process is employed to account for network losses, which are unavoidable in any realistic network implementation

Coaxial continuous transverse stub (CTS) array

A new coaxial continuous transverse stub (CTS) array is proposed, designed, constructed, and tested. It is an omni-directional low cost antenna array which provides good impedance matching characteristics and good tolerance to manufacturing errors. It can be simply fed by a coaxial connector and is particularly suitable for millimeter wave personal communication systems (PCS). It is shown that this type of radiating element provides high percentage of radiation, and for the simulated design of single- and multiple-element arrays, S/sub 11/ was below -10 dB across a 6 GHz frequency span at the Ka band. A three-element prototype coaxial CTS antenna array was designed, constructed, and tested in the X-band. Experimental results were in good agreement with the simulated performance. Potential application of this new antenna array in multiband operation is also described.

An implementation of a direction-finding antenna for mobile communications using a neural network

Direction-finding systems for radio signals are mostly used in mobile communications and avionics applications for antenna tracking or navigation purposes. In general, such systems require accurate calibration and may be sensitive to noise and external interference. In this paper, we investigate the performance of a neural network-based direction-finding system under such conditions. The proposed topology is a hybrid one, combining a simple RF signal beamformer with a neural network. The training of the neural network is accomplished experimentally with a three-element antenna array by varying the beam's direction and the carrier frequency. The error on the estimated direction of arrival caused by the environment and training limitations are investigated.

A Practical Calculator for Directional Antenna Systems

Herein is described a calculator that will aid the engineer in finding two- and three-element antenna arrays to meet his specific need. It can be constructed in a small pocket size for field estimation in adjusting arrays or in the form of a large instrument for precise calculations in design work. The operation of the machine in calculating ground-wave and sky-wave patterns is described, based on the radiation distribution of the various-height towers. The procedure is continued through the determination of the actual field strength to be expected from the array at any point, as well as the root-mean-square field strength of the system. The main idea is to proceed from the problem to the answer by the most direct method, while considering all the parameters.