Passive Phased Array Research Articles

A numerical study of Lamb wave localization in thin plates using a passive co-linear phased array

Lamb waves have become increasingly popular in the field of aerospace vehicle non-destructive testing and evaluation as well as structural health monitoring. These guided waves possess the ability to travel long distances and exhibit a notable inclination to interact with existing damage. This work has numerically explored for the first time the use of a passive co-linear phased array to localize emission sources over a wide range of variables. Three localization methods are explored, namely, reverse beamforming, wavefront curvature ranging, and hyperbolic lateration in a direction comparison without modeling transducers. It was shown that both reverse beamforming and wavefront curvature ranging could localize an emission with <1% error in both range and bearing, while hyperbolic lateration was significantly worse. A relationship between bearing error and bearing was demonstrated, presenting the ability to develop new methods with correction factors that can localize emissions with even greater accuracy.

The main directions of enhancement of digital antenna arrays

The development of modern radio electronic systems causes an increase in the requirements for the parameters of antenna devices (AU) and causes the transition from previously used mirror antennas and passive phased array antennas (FAA) to active FAA (AFAA), the considerable advantage of which is a significant reduction in energy losses of transmitted and received signals by reducing the distance of the low-noise amplifier input and output of power amplifier to the antenna element. Further development of the AU is the transition from AFAA with analog beamforming to digital antenna arrays (DAR) with digital beamforming, the advantages of which are due to the possibility of forming multibeam receiving and transmitting radiation patterns with independent control of the direction and shape of the beams, as well as the possibility of flexible change of operating modes. The use of a DAR with two-dimensional electronic scanning provides a significant increase in the efficiency of radio-electronic systems. Thus, their use in radar provides a gain in the efficiency of using the time, energy, frequency and spatial resources of radar with CAR up to 13 times compared with radar with passive FAA and AFAA with one-dimensional scanning. The disadvantages of the DAR are the high cost and increased energy consumption due to the installation of active elements in each transceiver channel, as well as the long time required to create new products, associated with a large amount of software and a complex structure for building a CAR. To overcome these disadvantages, manufacturers of antenna arrays and developers of the radio-electronic element base are creating new technical solutions. The main directions of development of technologies for the production of DAR functional devices that reduce the cost and reduce the time needed to create new products are shown: the development of common modules that allow you to create scalable DAR, increasing the integration of microwave monolithic integrated circuits with the placement of the maximum number of transceiver channels on one chip, increasing the integration of ASIC, including ADCs, DACs and digital signal processing devices, increasing the clock frequencies of digital functional nodes, as well as the development of circuit solutions for building nodes with low energy consumption.

On enhancing the noise-reduction performance of the acoustic lined duct utilizing the phase-modulating metasurface

This work proposes a noise-reduction structure that integrates phase-modulating metasurface (PMM) with acoustic liners (ALs) to enhance the narrow band absorption performance of a duct with relatively small length-diameter ratio. The PMM manipulates the wavefront by introducing different transmission phase shifts based on an array of Helmholtz resonators, so that the spinning wave within the duct can be generated. Compared with the plane wave, the generated spinning wave has a lower group velocity, which results in a greater traveling distance over the ALs in the duct. The optimization design is performed to determine the final structural parameters of the PMM, which is based on the predictions of the amplitude and phase shift of the acoustic wave at the outlet of the PMM using the theory of passive phased array. With the manipulation of the PMM, the incident plane wave is modulated into a spinning wave, and then enters into the acoustic liner duct (ALD), whose structural parameters are optimized by maximizing the transmission loss using the mode-matching technique. Finally, the noise-reduction performance of this combined structure is evaluated by numerical simulations in the presence of grazing flow. The results demonstrate that, compared with the traditional ALD, the proposed structure exhibits a significant increase in transmission loss within the considered frequency band, especially near the peak frequency of the narrow band noise.

Tunable acoustic passive phased array based on double-opening resonant rings

The special structural design of acoustic metamaterials further extends acoustic properties of the materials. We design a tunable acoustic passive phased array based on double-opening resonant rings, which modulates the acoustic waves only by the rotational angle, making up for the defect of the fixed structure of ordinary metamaterials. The rotation angle is selected based on the generalized Snell’s law, which not only enables focusing in a large frequency band range but also meets the focusing demand of acoustic waves incident at different angles and controls the position of the focal point.

Integrated factor of efficiency of antenna system using in the radar

Integrated efficiency factors are used not only at the design stage, but also in the case of choosing a ready-made system. In this case, the purpose of the research is to get an answer to the question of the expediency of its purchase (deployment), or monitoring the effectiveness of the system during its operation and developing proposals for optimizing the ways of its use and modernization. Since any system has limited resources when solving assignment tasks, it is necessary to develop a generalized efficiency factor from the standpoint of analyzing the effective allocation of radar resources when using antenna systems of various types in its composition. The aim of the article is to increase the efficiency of the use of radar resources in the antenna system. Achieving this goal includes solving the following tasks: substantiation of an integrated efficiency factor of the use of the antenna system in the radar, the use of an integrated efficiency factor to compare different types of antenna systems in the radar. А comparison of the efficiency of using a digital antenna array (DAA) with two-dimensional electronic scanning of the radiation pattern and parallel space surveillance, a reflector antenna, a passive phased antenna array with one-dimensional scanning, as well as an active phased antenna array with one-dimensional scanning and parallel space surveillance has been performed. It has been shown that the efficiency of using a DAR with two-dimensional electronic scanning is 2.3...15.6 times higher than the efficiency of other types of antenna systems. The proposed efficiency factor makes it possible to compare the efficiency of the use of radar resources when using different types of antenna systems, taking into account the features of their construction and the requirements for the purpose of the radar.

Compact and Low Power-Consumption Solid-State Two-Dimensional Beam Scanner Integrating a Passive Optical Phased Array and Hybrid Wavelength-Tunable Laser Diode

Large-scale optical phased arrays have attracted attention as devices for solid-state beam scanning employing light detection and ranging. However, conventional optical phased arrays using electro-optic phase shifters require active phase control for each antenna. Because the power consumption of the active phase shifters is proportional to the number of antennas, the total power consumption increases in a large-scale optical phased array with a narrow beam divergence. In this study, we propose a passive beam scanner that realizes two-dimensional beam scanning through the wavelength sweep of a laser light. Additionally, most studies on optical phased arrays use external laser diodes as light sources. This increases the size of the beam-scanning system. Therefore, there is a demand for integrating an optical phased array and a laser light source in a combined chip. In this study, we integrated a 64-channel passive optical phased array and a hybrid wavelength-tunable laser diode into a combined chip. The size of the device was 5 mm × 1.5 mm, and the power consumption for beam scanning was 49.3 mW. The field of view was 44.2° × 13.7°, and the full width at half maximum of the beam divergence was 0.517° × 3.67°. Compared with the device used in a previous study, our device was nine times smaller, and the total power consumption was only tens of milliwatts. This device consumes less power and achieves a fully integrated light detection and ranging.

Увеличение эффективности обнаружения воздушных судов на догонных курсах в импульсно-доплеровских бортовых РЛС с малой высотой полета носителя

Problem statement. The effectiveness of solving the problem of warning about possible collisions of small aircraft or unmanned aerial vehicles intended for the development of hard-to-reach territories depends on the time of early detection of another aircraft on intersecting trajectories. As a result of the comparative analysis of radar detection methods carried out in the article, taking into account the differences in the signal-interference situation characteristic of on-board pulse−Doppler radars for targets on catch-up courses in versions "multiple input - multiple output", "with joint a posteriori processing of results" and in traditional radar with active or passive phased antenna arrays have shown that the latter have energy advantages. Therefore, for this category of pulse-Doppler radars, a method for estimating the detection range on several frames is presented, which allows you to choose the logic of operation with an increase in the detection range. Research methods. The theory of antenna arrays and the theory of radar detection for pulse-Doppler radars were actively used in the work with the specified requirements for the probabilities of correct detection, false alarm and the selected model of fluctuations of the reflected useful signal. Purpose. To substantiate the advantages of technical solutions based on a traditional technical solution with phased antenna arrays for detection on catch-up courses and to develop recommendations for finding conditions that allow to increase the detection range. Results. The simulation results are presented, showing an improvement in the conditions for radar detection in onboard pulse-Doppler radars when finding the spectrum of the reflected radar signal in the Doppler frequency range, on which the spectrum of the reflected signal from the Earth's surface is superimposed when using radar with phased antenna arrays compared with spatial processing methods in MIMO and radars with joint a posteriori processing of results. A method for calculating the detection range on several adjacent frames has been developed and it is shown that in this case a longer range is achieved compared to the case of detection on a single frame. Practical significance. The results of the work can be used in small-sized onboard pulse radars of low-altitude carriers in order to increase the time of early warning of the presence of other aircraft on the flight path. This task seems to be especially relevant when flying radar carriers in hard-to-reach, developed territories.

Two-dimensional beam scanning of passive optical phased array based on silicon nitride delay line

Optical phased array has become a potentially critical component for beam scanner benefiting from its advantages in cost, mass production, integration, stability and scanning rate. However, the practicalization of OPA still has some great challenges, such as complex circuit control and the need for pre-calibrated phase. In this paper, we propose two passive OPA chips based on silicon nitride delay lines, which can achieve two-dimensional scanning only by wavelength tuning. The two passive OPA chips have different delay line lengths between 128 channels, achieving 2D scanning efficiency of 0.44°/nm×0.07°/nm and 0.87°/nm×0.07°/nm. The beam quality of both passive OPA chips is excellent, with a side lobe level of about 12 dB, without any degradation compared to the OPA chip without the delay line. The delay length of the proposed passive OPA chip can be further increased to obtain denser 2D scans, thereby improving the practicality of the OPA chip.

Demonstration of 2D beam steering using large-scale passive optical phased array enabled by multimode waveguides with reduced phase error

Optical phased arrays (OPAs) have received considerable attention as solid-state beam scanners. However, conventional OPAs that actively control the phase difference between arrays are characterized by excessive power consumption for high-precision beam emission. In this study, we fabricated an OPA comprising Bragg grating and arrayed waveguide grating (AWG). Multi-mode waveguide is used in AWG to reduce the effect of manufacturing error. This device realizes wide and high-resolution two-dimensional beam steering only by sweeping wavelength. FWHM of the emitted beam is 0.534° × 2.27°, and the steering range is 43.9° × 13.5° with 1/64 of the power consumption of conventional OPA.

Demonstration of beam steering using a passive silica optical phased array with wavelength tuning.

We demonstrate beam steering using a passive silica optical phased array (OPA) with wavelength tuning. In this OPA, a constant path difference is built up to assign sequential phase delays with a wavelength variation in arrayed waveguide channels for the beam steering. From as-fabricated 1 × 101 passive silica OPA chips, we successfully achieved beam forming with a transversal divergence angle of 0.57° at a 1548.3-nm wavelength and also beam steering of 15.4° by wavelength tuning of 30.7 nm. Combining a cylindrical lens in front of the end-fire radiators, the longitudinal divergence angle could be reduced from 13.0° to 0.42°. The side-mode suppression ratio of the beam was 10.3 dB at the center position. Through simulation, we analyzed the effects of the phase errors on the beam quality, due to the effective index fluctuation of the waveguide channels, and provided an allowable error range to attain beam forming from the passive OPA.

Guest Editorial Low-Cost Wide-Angle Beam-Scanning Antennas

One of the key antenna requirements in many modern wireless systems for communications and sensing is wide-angle beam-scanning <xref ref-type="bibr" rid="ref1" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[1]</xref> . The traditional method to achieve wide-angle beam-scanning is to employ mechanically controlled reflectors or lenses, which are bulky, heavy, and suffer from slow beam scanning speed. Other important limitations of mechanical scanning antennas include the lack of multi-beam scanning capability and the ability to conform with non-planar structures (conformal geometries), which are essential in a number of emerging systems requiring very low-profile antennas. An alternative technique is to employ electronically beam-scanning antennas using passive or active phased arrays <xref ref-type="bibr" rid="ref1" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[1]</xref> . Main disadvantages of phased arrays are high complexity, high power consumption, and high cost due to a large number of radio frequency (RF) or microwave phase shifters and T/R modules required. The problems worsen for phased arrays at millimeter-wave, sub-THz, and THz frequencies, due to significant losses in phase shifters and feed networks at higher frequencies combined with lower efficiency of power amplifiers <xref ref-type="bibr" rid="ref2" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[2]</xref> . The digital beamforming approach is even more costly and energy hungry due to the employment of large number of RF modules and digital devices <xref ref-type="bibr" rid="ref1" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[1]</xref> , <xref ref-type="bibr" rid="ref3" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[3]</xref> , <xref ref-type="bibr" rid="ref4" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[4]</xref> .

Thickness-designable acoustic metamaterial for passive phased arrays

Passive phase-controlled acoustic arrays based on metamaterial surfaces artificially manipulate acoustic waves, which can be used in biomedical imaging and nondestructive testing. One of the most representative applications is ultrasonic therapy using a passive phased array within a complete 2π phase. In contrast, the surface thickness is 1/10 the wavelength of the operating frequency. However, conventional design methods feature a fixed array thickness for a specific frequency. This becomes necessary for different application scenarios where different thicknesses are needed. This study proposed a labyrinth resonant cavity metascreen phased array based on Helmholtz resonators and convoluted labyrinth acoustic metamaterials. The thickness of this array can be optimized to accommodate a specific operating frequency to achieve full 2π phase control by adjusting only one parameter. Theoretical simulations and experimental results verified the acoustic wave manipulation effect. The proposed method may find utility in applications for noninvasive ultrasonic therapy, including nondestructive testing, acoustic communication, and biomedical imaging.

Positioning precision analysis of passive phased array radar localization for construction safety monitoring in a non-line-of-sight environment via heatmap

A positioning system for complex construction scenarios is necessary to apply due to the limitations of the traditional positioning system in a non-line-of-sight (NLOS) environment, in order to study the impact of obstacles on construction sites. A quantitative measurement experiment of positioning precision in an NLOS environment was conducted in a petrochemical construction site, and a large number of engineering data were obtained, which showed the feasibility of a Passive Phased Array Radar - Bluetooth Hybrid Positioning System (PPAR-B HPS). The novelty of this paper is to propose a simplified signal coverage model for rapid measurement via the analysis of on-site data of the petrochemical industry and analyze the factors affecting the positioning precision in NLOS environment via a positioning precision heatmap analysis method to promoting the development and application of positioning technology in construction sites. The effectiveness of these methods are proved by empirical and comparative research.

Power control and beamforming in passive phased array radars for low probability of interception

In this paper, we investigate low probability interception (LPI) in passive phased array radars. Power control and transmit beamforming (BF) are used to minimize the received power by the interceptor. Meanwhile, desired target detection performances and the limited power budget of radar are guaranteed. The LPI problem is solved analytically and some theorems are derived for the design of optimum BF weights. Two LPI optimization problems from different perspectives are formulated and solved analytically in preparing closed-form solutions for designing transmit BF weights. LPI performance and computation time of the proposed algorithms are compared with that of the benchmark algorithms. Simulation results show that proposed algorithms not only minimize the interception probability of radar in comparison with benchmark algorithms but also satisfy desired detection performance and power budget constraints simultaneously. The proposed algorithms outperform the standard numerical Barrier algorithm in complexity and optimality.

An Enhanced Smoothed L0-Norm Direction of Arrival Estimation Method Using Covariance Matrix.

An enhanced smoothed -norm algorithm for the passive phased array system, which uses the covariance matrix of the received signal, is proposed in this paper. The SL0 (smoothed -norm) algorithm is a fast compressive-sensing-based DOA (direction-of-arrival) estimation algorithm that uses a single snapshot from the received signal. In the conventional SL0 algorithm, there are limitations in the resolution and the DOA estimation performance, since a single sample is used. If multiple snapshots are used, the conventional SL0 algorithm can improve performance in terms of the DOA estimation. In this paper, a covariance-fitting-based SL0 algorithm is proposed to further reduce the number of optimization variables when using multiple snapshots of the received signal. A cost function and a new null-space projection term of the sparse recovery for the proposed scheme are presented. In order to verify the performance of the proposed algorithm, we present the simulation results and the experimental results based on the measured data.

Multifunctional Asymmetric Sound Manipulations by a Passive Phased Array Prism

Asymmetric acoustic manipulations (AAMs) attract increasing attention for applications in integrated and architectural acoustics. However, because a planar phased array system has the same phase distribution on both sides, designing a monolayer device with asymmetric phase modulation is a real challenge. This work experimentally realizes four types of phased array prisms with different AAM effects arising from asymmetric phase distributions, created by different exit interfaces on either side of a prism. With broad bandwidth, multifunctional AAMs, passive structure, and easy fabrication, these prisms offer a fresh approach to creating $e.g.$ multifunctional acoustic rectifiers and diodes.

Phased array Doppler reflectometry at Wendelstein 7-X.

A passive phased array Doppler reflectometry system has recently been installed in the Wendelstein-7X stellarator. In contrast to conventional Doppler reflectometry systems, the microwave beam can be steered on short time scales in the measurement plane perpendicular to the magnetic field in the range of ±25° without mechanical steering components. This paper characterizes the design and properties of the phased array antenna system and presents the first measurement results from the latest OP1.2a campaign.

The increase of signal-to-noise ratio in the spatial separation of signals by the curvature of the wavefront

The article presents the results of the research of the dependence of the signal-to-noise ratio in the focal spot of the reflecting passive phased antenna array (PPAA), made of planar diffraction elements, on the orientation of the PPAA relative to the structure of the interference field, its dimensions and distance from PPAA plane to the focal spot. The results of the research show that the signal-to-noise ratio mainly depends on the horizontal size of the PPAA. The increase of the vertical size of the array leads to the fact that the focal distance corresponding to the maximum of the signal-to-noise ratio increases with the practically unchanged value of this maximum.

Features of excitation reconstruction in flat multielement phased antenna array face using dynamic directional patterns

The study focuses on reconstructing the amplitude-phase distribution of flat multielement passive and active phased antenna arrays with the use of dynamic radiation patterns, measured with electronical scanning without mechanical rotations and antenna movements. The paper describes the measurement settings of dynamic radiation patterns, necessary for reconstructing the amplitude-phase distribution. Findings of the research show that to reconstruct the amplitude-phase distribution according to dynamic radiation diagrams, there is no need for increased computational resources due to the use of Fourier transformation algorithms. After the method was experimentally verified on the specific samples of active phased antenna arrays, its high efficiency was established. The paper gives the examples of reconstructing the amplitude-phase distribution from dynamic radiation patterns in the presence of malfunctions in active phased array antennas.

Metamaterial-based passive phased arrays: Resolution, losses, and characterization

Metamaterial and metasurface-based passive phased arrays provide novel means for the manipulation of acoustic fields. As passive elements, metasurfaces can provide local phase delays which enable the steering of sound fields and facilitate extraordinary wave phenomena. Some aspects that affect the performance of these passive elements include the spatial resolution/aliasing effect, the component resonances that shape the transmission spectra, and the thermoviscous losses that limit the transmission efficiency [X. Jiang, L. Yong, and L. Zhang, J. Acoust. Soc. Am. 141(4), EL363–368, April 2017]. Efficient acoustic field characterization is essential for investigating these issues with the ultimate aim of optimizing the geometrical parameters of the structure. This talk will address some details of the physics of metamaterial-based passive arrays and the broadband approach for assessing their transmission properties, with the aim of improving the design cycle and exploring novel uses.