Antenna Array For Applications Research Articles

Simulation of microstrip radio altimeter antenna for aircraft

The purpose of the article is to carry out mathematical modeling of the main characteristics and parameters of a microstrip antenna, the dielectric substrate of which is created from a domestic ceramic sample and to substantiate the use of a microstrip antenna as a transmitting and receiving antenna in a radio altimeter. It is shown that a microstrip antenna on a ceramic material substrate with a relative permittivity ε = 9.6 and a thickness of 0.2 mm has good electrical parameters in the frequency range of 31.5–33.5 GHz. Including the width of the antenna radiation pattern at the level of –3 dB is 12.5 degrees in the horizontal plane and 26.7 degrees in the vertical plane. In this case, the antenna gain is 17 dB and the level of the first side lobe is –20 dB relative to the main antenna lobe. Also the practical application of microstrip array antennas inphase as a transmitting and receiving antenna for a radio altimeter installed on aircraft is described in the article. The range of the altimeter reaches 300 m.

3D printed lattice structure for lightweight Ka‐band phased array antenna

Here a lightweight antenna array is designed and fabricated for a Ka-band phased array antenna. From the perspective of advanced space-borne engineering practice, a Kagome lattice structure is proposed for the lightweight antenna array applications and the representative configurations of the proposed lattice structure is fabricated via selective laser melting (SLM). Experiment is performed to estimate the electrical performance with the featured structure. Compared with the conventional antenna array, the proposed one has 69% less weight, identical measured radiation patterns, and good electrical performance. The results demonstrate the great potentials for other readily customized lightweight phased array antenna applications.

A high gain and compact transmitarray antenna for Ku-band satellite communications

ABSTRACT This work focuses on designing a low-profile frequency selective surface transmitarray antenna at 12 GHz using a four-layer Split Ring Resonator structure. The parametric analysis shows a high transmission coefficient magnitude of −2.38 dB and 349-degrees phase range. X-band horn antenna is used as a feed source to illuminate the Frequency Selective Surface (FSS) transmitarray layers. Each FSS layer is comprised of 121 elements. The measured results show a wide impedance bandwidth of 35%, a high gain value of 21.9 dBi and 11.6% 1-dB bandwidth. The proposed design can be used in high gain array antenna applications, particularly Ku band Satellite communication systems.

Dot-Shaped 3D Range-Angle Dependent Beamforming With Discular Frequency Diverse Array

A frequency diverse array (FDA) concept has drawn substantial attention in recent years because of its particular range-angle-dependent beam pattern. This interesting feature promises new opportunities and capabilities for antenna array applications, especially in beamforming. The dot-shaped beam pattern is also a new and exceptional phenomenon that can focus the transmit energy in a 3-D spatial region of interest. However, almost all of the works and studies in the literature with this title is related to the linear array geometry and involves range and one angle only. Therefore, the beam defined as dot-shaped is actually only 2-D and extends in one angle, thus breaking the dot shape. Moreover, to obtain such a beam shape, complex mathematical techniques and algorithms are used. In this study, a real 3-D dot-shaped beamforming is realized with discular FDA (DFDA) and outward radial frequency offsetting scheme. This study extends the research geometries of frequency diversity concept further by investigating the discular geometry in-depth. The theory, analysis, and the basic beam-steering properties of the DFDA is presented and compared with other geometries.

Filter-Free Photonic Image-Rejection Down-Conversion for Distributed Antenna Applications

Photonics-assisted frequency conversion based on cascaded modulators is an effective way to satisfy the requirements of distributed antenna array applications. A filter-free photonic image-rejection down-converter with immunity to dispersion-induced power fading is proposed and demonstrated. The radio frequency (RF) signal from the distributed antenna unit is injected into a dual-drive Mach–Zehnder modulator (DDMZM) through an electrical 90° hybrid coupler (HC), and a single-sideband (SSB) signal is realized. It is then transmitted to the center office by an optical fiber link. At the center office, the modulated RF signal is injected into a dual-polarization dual-parallel MZM (DP-DPMZM) after a polarization controller (PC). Afterwards, an LO signal remodulates it through the Y-DPMZM, and carrier-suppressed SSB modulation is fulfilled via another electrical 90° HC. After the power splitting, quadrature I and Q IF signals can be obtained by a photonics-based continuously adjustable phase shifter. Through a combination of the I/Q IF signals with a low-frequency electrical 90° HC, a photonics image-rejection down-converter based on phase cancellation is realized. Moreover, no optical filter is required; thus, the image-rejection down-converter can work with a large bandwidth. The proposed filter-free photonic image-rejection down-converter is theoretically analyzed and experimentally verified.

A Compact Wideband Planar Magic Tee for Monopulse Antenna Array Applications

This letter presents a compact, wideband, planar, E-arm folded magic tee at $Ku$ -band for monopulse slotted waveguide antenna array applications. A novel impedance matching structure, an L-shaped septum, is implemented at the magic tee junction, which results in wide impedance bandwidth at all ports. The height of this septum is the same as that of the waveguide height, which allows the design to be very compact. An impedance bandwidth of 22% is achieved for a return loss of 20 dB. The magic tee is manufactured using a high-precision electric discharge machining (EDM) process and followed by the integration of subparts using silver epoxy bonding. Simulation and measured results are compared. Measured amplitude balance of < 0.1 dB, phase balance of <2°, and isolation of better than −35 dB have been achieved. The proposed design is a good technique for the design of broadband, miniaturized monopulse comparators for monopulse antenna array applications.

Taylor Expansion and Matrix-Based Interval Analysis of Linear Arrays With Patch Element Pattern Tolerance

In this study, a novel interval analysis (IA) approach for linear arrays with element pattern tolerance is proposed. This study differentiates itself from the classic interval analysis (CIA) method because it focuses on the effects of the array element (e.g., patch) pattern tolerance on the antenna array pattern; the tolerance may be caused by fabrication errors in the element. The closed-form pattern expressions of the element (e.g., patch) and array are deduced by the interval arithmetic method. To mitigate the interval extension (also referred to as the overestimation problem) caused by the dependency problem, Taylor expansion and matrix-based interval analysis (TMIA) methods are proposed and implemented in this study. A set of numerical examples is reported and analyzed to indicate the effectiveness of the proposed TMIA approach with the results of Monte Carlo (MC) and CIA methods, as well as to indicate its potential capabilities and advantages in the actual application of industrial antenna arrays.

A cost-effective beam forming structure for global navigation satellite system multipath mitigation and its assessment

AbstractArray antenna beam forming has high potential to improve the performance of the global navigation satellite system (GNSS) in urban areas. However, the widespread application of array antennas for GNSS multipath mitigation is restricted by many factors, such as the complexity of the system, the computation load and conflicts between required performance, cost budget and limited room for the antenna placement. The scope of this work is triplicate. (1) The pre-correlation beam forming structure is first suggested for multipath mitigation to decrease the system complexity. (2) With the pre-correlation structure, the equivalence of adaptive beam forming to quiescent beam forming is revealed. Therefore, the computational load for beam forming is greatly decreased. (3) A theoretical model is established to link the benefits of beam forming with GNSS performance improvement in terms of pseudorange quality. The model can be used by industry to balance the aforementioned restrictions. Numerical results with different array settings are given, and a 2 × 2 rectangle array with $0.4\lambda $ element spacing is suggested as a cost-effective choice in GNSS positioning applications in urban canyon areas.

3D Printed Wideband Multilayered Dual-Polarized Stacked Patch Antenna With Integrated MMIC Switch

Capability of 3D printing for developing wideband multilayered antenna systems packaged with active RF circuit components remains relatively unexplored. To address this gap, this manuscript demonstrates wideband patch antenna that is integrated with a polarization selection switch. Antenna bandwidth is enhanced with customized substrate thicknesses and stacked patch layers. Switch is integrated with 3D vertical transitions to achieve wide bandwidth, smaller packaging, and low-loss. To enable future antenna array applications, a detailed investigation is also presented to maximize the performance of the microstrip feed lines by adjusting the substrate thickness and deposition process. The antenna consists of 13 dielectric and conductive layers. Specifically, the manuscript demonstrates the lowest attenuation in the literature for a fully printed microstrip line with 0.25 dB/cm measured loss at 18 GHz. The antenna operates with more than 80% radiation efficiency and 45% bandwidth. The polarization switch is embedded within the antenna structure. The antenna retains a high cross-polarization ratio of ~20 dB due to 3D feed line transitions and symmetric location of the switch with respect to the antenna feeds.

Single-Antenna-Based GPS Antijamming Method Exploiting Polarization Diversity

The vulnerability of Global Positioning System (GPS) receivers to jammers is a major concern owing to the extremely weak received signal power of GPS. Researches have been conducted on a variety of antenna array techniques to be used as countermeasures to GPS jammers, and their antijamming performance is known to be greater than that of single antenna methods. However, the application of antenna arrays remains limited because of their size, cost, and computational complexity. This study proposes and experimentally validates a novel space-time-polarization domain adaptive processing for a single-element dual-polarized antenna (STPAPS) by focusing on the polarization diversity of a dual-polarized antenna. The mathematical models of arbitrarily polarized signals received by dual-polarized antenna are derived, and an appropriate constraint matrix for dual-polarized-antenna-based GPS antijam is suggested. To reduce the computational complexity of the constraint matrix approach, the eigenvector constraint design scheme is adopted. The performance of STPAPS is quantitively and qualitatively evaluated through experiments as follows. 1) The carrier-to-noise-density ratio (C/N0) of STPAPS under synthetic jamming is demonstrated to be higher than that of the previous minimum mean squared error (MMSE) or minimum variance distortionless response (MVDR) based dual-polarized antenna methods. 2) The strengths and weaknesses of STPAPS are qualitatively compared with those of the previous single-element dual-polarized antenna methods that are not based on the MMSE or MVDR algorithms. 3) The characteristics of STPAPS (in terms of the directions and polarizations of the GPS and jamming signals) are compared with those of the conventional two-element single-polarized antenna array method, which has the same degree of freedom as that of STPAPS.

Decoupling Between Extremely Closely Spaced Patch Antennas by Mode Cancellation Method

In this article, an inductance-based decoupling scheme is proposed to reduce the mutual coupling between extremely closely spaced microstrip antennas. The original strong coupling can be effectively suppressed by simply inserting a lumped inductance in between. To offer a systemic design guideline for this decoupling strategy, a mode cancellation method, based on the synthesis of common mode (CM) and differential mode (DM), is proposed. The inserted inductance plays a role of tuning CM and DM impedances to a similar status, which has an equivalent decoupling effect according to the theory of microwave network. Alternatively, the lumped inductance could also be replaced by an inductive connecting strip for a concise topology. To validate the proposed decoupling concept, a prototype is simulated, fabricated, and measured. The experimental results show that the poor isolation of 5 dB is improved to better than 15.4 dB across the entire matched bandwidth of 2.394-2.530 GHz, with an extremely close edge-to-edge distance of 0.016 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> and center-to-center distance of 0.44 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> . Furthermore, the validation of extending to large-scale 1-D and 2-D arrays is also discussed. Featuring simple structure, compressed dimension, strong-coupling suppression, and good radiation performance, the proposed decoupling scheme possesses promising potential for antenna array applications.

Optical single-sideband polarization modulator based on Sagnac interferometers and its applications in radio-over-fiber systems

A novel scheme to implement an optical single-sideband (OSSB) polarization modulator (PolM) is proposed and theoretically demonstrated in this paper. The proposed OSSB-PolM is based on the phase modulation technique in two consecutive Sagnac interferometers (SIs). It is shown that by applying four equal-power radio frequency (RF) signals with appropriate phases to electro-optic modulators and aligning the polarization state of the modulated signal in the proper direction, an OSSB-PolM signal will be generated. The proposed scheme can find many microwave photonic (MWP) applications. To show this, an OSSB modulator with tunable optical carrier-to-sideband ratio, an OSSB-suppressed carrier modulator/optical frequency shifter, and a full-ranged MWP phase shifter are proposed and demonstrated. The proposed structure includes several important advantages. For instance, the system is free from the limitations caused by optical/electrical filters. Since the propagating lights in an SI traverse the identical optical path in clockwise and counterclockwise directions, the system is immune to environmental perturbations. Furthermore, there is no need for a bias control circuit, so the system has a stable operation. In addition, the proposed scheme can be extended to multichannel applications in array antennas. Theoretically, calculations have been verified by simulation results.

Synthesis of an Interference-Resistant Space-Time Filter for High-Precision Measurements of Navigation Parameters According to the Signals of Global Navigation Satellite Systems

We study the problems of serviceability of contemporary high-precision terminals of global navigation satellite systems under the conditions of jamming and spoofing interferences. The application of digital antenna arrays with algorithms of space-time signal processing of the signals can be regarded as a solution of the problem of low interference resistance. We describe well-known, most studied, and currently applied algorithms of space-time signal processing. We also formulate the causes that do not enable one to use well-known algorithms in high-precision terminals of satellite systems of global navigation. We propose an algorithm of space-time signal processing based on a space-time filter of finite length with a theoretically justified requirement of Hermitian symmetry for the matrix impulse response. The proposed algorithm guarantees the absence of distortions of signals under any signal and interference conditions. In this case, the impulse response of the space-time filter is computed according to the criterion of optimal suppression of the interference. The characteristics of the proposed space-time filter and other algorithms of space-time signal processing are investigated. For this purpose, we apply the method of mathematical simulation with random search of numerous parameters of signals and interferences (directions to signals, directions to numerous interferences, and to their reflections, remoteness of the reflectors of interferences, the phases of reflections, and the levels of interferences and reflections, etc.). The results of simulations are presented in the form of the distribution functions of the signal-to-interference ratios at the output of the algorithms of space-time signal processing and the distribution functions of the phase and signal-time biases. The obtained dependences substantiate the absence of the phase and signal-time biases in the space-time filter for any signal and interference conditions with interference multipath. It is shown that the space-time filter guarantees a higher interference resistance than the compensating algorithms of space-time signal processing.

Antenna Decoupling by Common and Differential Modes Cancellation

In this article, a general decoupling method based on a new perspective of common mode (CM) and differential mode (DM) cancellation is proposed. For two closely spaced antennas, the mutual coupling effect can be analyzed and solved by exciting them simultaneously with in-phase (CM) and out-of-phase (DM) signals. It is theoretically proved that, if CM and DM impedances are the same, the mutual coupling effect between two separated antennas can be totally eliminated. Therefore, we can solve the coupling problem by CM and DM impedance analysis and exploit the unique field properties of characteristic modes to assist in antenna decoupling in a physical intuitive way. To validate the feasibility of this method, two practical design examples, including the decoupling between closely spaced dipole antennas and planar inverted-F antennas, are proposed. Both design examples have demonstrated that the proposed method can provide a systemic design guideline for antenna decoupling and achieve better decoupling performance compared to the conventional decoupling techniques. We forecast the proposed decoupling scheme, with a simplified decoupling procedure, has great potential for the applications of antenna arrays and multi-input multi-output (MIMO) systems.

Miniaturization of patch antenna based on hybrid topology optimization

A hybrid topology optimization method that combines the scalar isotropic material with penalization and the level set method is utilized to achieve the miniaturization of patch antennas while maintaining good radiation and polarization characteristics. In order to achieve this goal, the Heaviside projection filter is applied to obtain topologies that are more complex. Both the radiation power and the reflection coefficient of the antenna are utilized as sub-objectives. Besides, by setting the radiation patch to be symmetrical, not only the numbers of optimization variables and optimization sub-objectives are reduced, but also the cross-polarization level is suppressed effectively, so that the optimization is accelerated. The optimized patch antenna achieves good performance in patch size, impedance matching, radiation pattern, gain, and polarization characteristics. Compared with the reference patch antenna, the patch size of the optimized antenna is reduced by 63%, while the maximum realized gain and efficiency remain basically unchanged, achieving more than 5.9 dBi and 90%, respectively. Due to its very small size patch, the antenna is particularly suitable for compact multi-antenna and antenna array applications.

A proposed optical frequency synchronization system for the South African MeerKAT radio telescope

Abstract The South African MeerKAT radio telescope, a precursor to the Square Kilometre Array (SKA) will be incorporated into the mid-frequency component of SKA Phase 1. After a decade of planning, designing and construction, the MeerKAT radio antenna was officially inaugurated in July of 2018. Several exciting astronomical phenomena have already been observed with the MeerKAT radio telescope. Images produced from radio waves collected by the telescope revealed a wealth of ground-breaking astronomical wonders. For radio antenna array applications, the image quality is associated to the accuracy and stability of the phase measurements. The MeerKAT radio instrument is no exception to this, as ultra-stable clock signals will be disseminated to remote dishes across optical fibre up to 12 km in length. In this paper, with the purpose of application to MeerKAT, we propose and demonstrate a novel frequency dissemination and synchronisation system using a vertical cavity surface emitting laser (VCSEL) based phase correction actuator together with the inherent chromatic dispersion properties of the fibre. Frequency dissemination stabilities of 4.44 × 10−12 at 1 s and 4.86 × 10−14 at 104 s were successfully measured across the 26 km G.655 fibre link.

Design and implementation of an adaptive beamformer for phased array antenna applications

AbstractA modular beamformer, fully scalable in amplitude and phase, to be used with transmitting antenna arrays operating in the Digital Cellular System (DCS)/Personal Communications Service (PCS) frequency band, is designed and fabricated in this paper. The implementation of the structure is simple and very low cost; its performance is evaluated by measuring the frequency response, as well as the radiation patterns produced by an antenna array connected to the output of the beamformer. The latter exhibits low return losses and average amplitude imbalance less than ±0.8 dB, whereas the phase deviations do not exceed ±6° on average, over its 300 MHz bandwidth.

Dual-Band Microstrip Corporate Feed Network Using an Embedded Metamaterial-Based EBG

This paper demonstrates the design and experimental validation of a dual-band microstrip (MS) corporate feed network using an embedded metamaterial-based electromagnetic bandgap (MTM-EBG) structure. The MTM-EBG is designed to appear as a $35.4~\Omega $ MS transmission line (TL) with a 90° electrical length at both 2.4 and 5.0 GHz. This structure is then used in place of a conventional single-band quarter-wavelength transformer in a $50~\Omega $ MS T-junction power divider, rendering it dual band with 10 dB return-loss fractional bandwidths of 82.3% and 12.0% at center frequencies of 2.4 and 5.0 GHz, respectively. The result of this modification shows a very good performance at both operating frequencies, as well as substantial rejection over a prescribed bandwidth of intermediate frequencies. The dual-band transformer formed by the embedded MTM-EBG is 30.5% miniaturized at 2.4 GHz relative to a conventional MS quarter-wavelength transformer, which indicates its potential for use in size-restricted scenarios and embedded filtering applications. A dual-band four-way corporate feed network is then formed by cascading the MTM-EBG-loaded T-junction power dividers, which is suitable for antenna array applications. This structure has an improved performance at 2.4 and 5.0 GHz compared to unloaded networks designed for these frequencies having the same overall size. The experimental 10 dB fractional bandwidth for the MTM-EBG-loaded corporate feed network was found to be 52.0% and 10.8% around 2.4 and 5.0 GHz, respectively.

Numerical study and experimental validation of a four-way feeding network with 45 deg broadband phase shifts for antenna array applications

Abstract A four-way network with 45 deg output phase shifts for feeding antenna array is studied in this work. To widen the phase imbalance, quarter wavelength short stubs with suitable characteristic impedances are introduced and numerically analyzed. Meanwhile, the wideband magnitude imbalance is also discussed by extending the inter-stage transmission line with proper electric length. The study is further confirmed by developing a prototype feeding network centered at 3 GHz. Results from the fabricated prototype network exhibit wideband good performance, both from numerical evaluations and experimental demonstrations.

A Directly Matched PA-Integrated $K$-Band Antenna for Efficient mm-Wave High-Power Generation

A $K$ -band slot antenna element with an integrated gallium nitride power amplifier (PA) is presented. It has been optimized through a circuit–electromagnetic codesign methodology to directly match the transistor drain output to its optimal load impedance ( $\mathrm{Z_{opt}} = 17+j46\; \Omega$ ), while accounting for the over-the-air coupling effects in the vicinity of the transition between the PA and antenna. This obviates the need for using a potentially lossy and bandwidth-limiting output impedance-matching network. The measured PA-integrated antenna gain of 15 dBi with a 40% total efficiency at 28 dBm output power agrees well with the theoretically achievable performance targets. The proposed element is compact ( $0.6 \times 0.5 \times 0.3\; \lambda ^3$ ) and, thus, well suited to meet the high-performance demands of future emerging beamforming active antenna array applications.