Planar Array Research Articles

Efficient High Gain Elliptically Polarized Phased MIMO Antenna

A phased MIMO antenna with a coaxial feed is designed to operate in the electromagnetic spectrum with the frequency range of 8 GHz to 12 GHz, which resonates at 9 GHz, is used in military and satellite communication. The ability of phased MIMO antennas to change the form and orientation of the radiation pattern without constantly moving the antenna is unique. The proposed approach can also improve radiation efficiency by maximizing array unit size. To validate the proposed method, an elliptical polarization phased antenna has been constructed as a planar array. A 2 to 2 planar dual polarized MIMO antenna is intended to improve the efficiency. The obtained return loss for 2x2 planar MIMO is -19.34 dB. The proposed 2x2 MIMO antenna is projected on a teflon material with dielectric constant of 2.25 and the thickness of the substrate is 7mm. The efficiency for two port MIMO antenna is 97.7%.

Design of a bulk-lead zirconate titanate ultrasonic transducer array addressing specific excitation modes

Conventional ultrasonic transducer arrays generally use simultaneous or delayed excitation methods to generate various types of wave fronts in ultrasonic testing. Such array excitation modes are relatively simple and unable to maximize the functions of the array elements or element apertures. Accordingly, this study developed a novel excitation ultrasonic transducer array with flexible excitation aperture. A minimum row-column-addressing planar array structure for ultrasonic transducers based on bulk lead zirconate titanate (PZT) was designed for industrial ultrasonic testing. In addition, a transducer structure design scheme and truth table for array addressing with excitation logic were provided. By performing an acoustic field simulation, this study analyzed the relationship between the longitudinal amplitude and resonant frequency of the array elements and the impedance distribution. The transducer was fabricated and packaged using a circuit board and bulk PZT array elements. Testing revealed that the resonant frequency of the array was 1.07 MHz, the effective electromechanical coupling coefficient was 0.40, and the fractional bandwidth of the pulse echo response and spectrum was 38.46%. Using an aluminum block, performance in single-element, row-, column-, and full-array excitation was tested, and echo curves were obtained for multiple apertures. Using a single-circuit module, the transducer realized flexible gating and excitation of the array elements. The research provided a new method for industrial ultrasonic transducer array design.

Simulation study of protoacoustics as a real-time in-line dosimetry tool for FLASH proton therapy.

Applying ultra-high dose rates to radiation therapy, otherwise known as FLASH, has been shown to be just as effective while sparing more normal tissue compared to conventional radiation therapy. However, there is a need for a dosimeter that is able to detect such high instantaneous dose, particularly in vivo. To fulfill this need, protoacoustics is introduced, which is an in vivo range verification method with submillimeter accuracy. The purpose of this work is to demonstrate the feasibility of using protoacoustics as a method of in vivo real-time monitoring during FLASH proton therapy and investigating the resulting protoacoustic signal when dose per pulse and pulsewidth are varied through multiple simulation studies. The dose distribution of a proton pencil beam was calculated through a Monte Carlo toolbox, TOPAS. Next, the k-Wave toolbox in MATLAB was used for performing protoacoustic simulations, where the initial proton dose deposition was inputted to model acoustic propagations, which were also used for reconstructions. Simulations involving the manipulation of the dose per pulse and pulsewidth were performed, and the temporal and spatial resolution for protoacoustic reconstructions were investigated as well. A 3D reconstruction was performed with a multiple beam spot profile to investigate the spatial resolution as well as determine the feasibility of 3D imaging with protoacoustics. Our results showed consistent linearity in the increasing dose-per-pulse, even up to rates considered for FLASH. The simulations and reconstructions were performed for a range of pulsewidths from 0.1 to 10μs. The results show the characteristics of the proton beam after convolving the protoacoustic signal with the varying pulsewidths. 3D reconstruction was successfully performed with each beam being distinguishable using an 8cm×8cm planar array. These simulation results show that measurements using protoacoustics has the potential for in vivo dosimetry in FLASH therapy during patient treatments in real time. Through this simulation study, the use of protoacoustics in FLASH therapy was verified and explored through observations of varying parameters, such as the dose per pulse and pulsewidth. 2D and 3D reconstructions were also completed. This study shows the significance of using protoacoustics and provides necessary information, which can further be explored in clinical settings.

Numerical Simulation of Metasurface Grating to Function as Polarization Modulator in Quantum Key Distribution Systems

Polarization modulation plays an important role in polarization encoding in quantum key distribution. By using polarization modulation, quantum key distribution systems become more compact and more vulnerable as one laser source is used instead of using multiple laser sources that may cause side-channel attacks. Metasurfaces with their exceptional optical properties have led to the development of versatile ultrathin optical devices. They are made up of planar arrays of resonant or nearly resonant subwavelength pieces and provide complete control over reflected and transmitted electromagnetic waves opening several possibilities for the development of innovative optical components. In this work, the Si nanowire metasurface grating polarizer is designed by COMSOL Multiphysics Software to operate in the visible region and transmit the transverse magnetic polarization of light. The same structure can be rotated by different angles, i.e., 90o, 45o, and -45o to mimic the function of polarization modulation in quantum key distribution systems. The designed structure has an extinction ratio of ~ 60000 and a wide angular tolerance range of (-20o - 20o).

Joint 3D coordinate and wave-speed estimation with nonuniform planar array: Multi-leak localization in gas pipe buried in sandy soil

The acoustic-based methods enable remote detection of gas pipeline leaks and provide the leak area. However, accurate localization of buried leaks within the leak area requires further investigation. In this scenario, the unknown wave speed in soils and the computational complexity associated with three-dimensional (3D) localization in underground spaces pose challenges. Therefore, a joint estimation method based on a specially-designed nonuniform planar array is proposed to determine both the leak position and wave-speed. Specifically, a small-aperture uniform subarray is embedded into the large-aperture nonuniform array. By utilizing the small-aperture subarray, we can solve for the relationship between wave-speed and direction of arrival (DOA) of far-field waves. Subsequently, two-dimensional spectrum estimation is performed using the large-aperture array to obtain estimates for both wave-speed and near-field source distance. Finally, without resorting to 3D spectrum estimation, the 3D coordinates of the leak are determined. Experimental results conducted on buried pipes demonstrate that the proposed method effectively works across three soil types at varying burial depths. Notably high accuracy is achieved using a large-aperture array expended from the uniform L-shaped array with RMSE less than 0.1 m at SNR of 15 dB. Both experimental validations and simulations confirm that the novel approach can be successfully applied in various scenarios.

Light absorption by a planar array of spherical particles and a matrix in which they are embedded: statistical approach.

The fractions of light energy absorbed by a 2D array of spherical particles and the matrix in which they are embedded are determined. The solution is based on a volume integral equation and a statistical approach. The absorption coefficient of the array is found via the internal fields of the particles. The absorption coefficient of a matrix is found as the difference between the absorption coefficients of the composite structure and the particles. Numerical results are presented for arrays of metal, semiconductor, and dielectric nano- and microparticles of short-range order and imperfect long-range order in the absorbing media at normal and oblique incidence of a plane wave.

Adaptive Beamforming for Cascaded Sparse Diversely Polarized Planar Array

Adaptive beamforming plays an increasingly vital role in various applications, including radar, sonar, telecommunications, and many other related fields. In this paper, we present an adaptive beamformer (called polarimetric Sparse-Reconstruction beamformer) based on cascaded sparse diversely polarized planar array. The cascaded sparse array consists of multiple parallel sparse linear subarrays, whose difference co-array has no holes. The beamformer is operated in the joint spatial and polarization domain; thus, can potentially suppress the interferences that are close to the desired signal with different polarization states. Two key building blocks of our proposed beamformer are polynomial rooting-based closed-form two-dimensional direction-of-arrival and polarization joint estimation procedures, where the involved polynomial coefficients are also derived. Then, the closed-form power distribution estimation is presented to reconstruct the interference-plus-noise covariance matrix by leveraging the sparsity of the desired signal and interferences in the joint spatial and polarization domain. Thus, the proposed adaptive beamformer is computationally efficient, since all the procedures involved are formatted by closed-form expressions. Finally, a set of simulation examples are given to evaluate the characteristics of the proposed cascaded sparse array as well as the performance and robustness of the proposed beamformer in different scenarios, and compared against several existing approaches.

Synthesis of Large Ultra-wideband Sparse Circular Planar Arrays Based on Rotationally Symmetric Structure

This article aims to improve the synthesis efficiency and radiation performance of large ultra-wideband (UWB) rotationally symmetric sparse circular planar arrays by using a modified differential evolution algorithm (MDEA). In the proposed MDEA, we adopt a new encoding mechanism in which an individual represents an element position expressed in polar coordinates. Importantly, such an encoding mechanism can facilitate the multiplication calculation for the array factor in the individual being updated while making it easier to meet the given minimum element spacing constraint. Moreover, to cater to the new encoding mechanism, some low-dimensional evolution operators are introduced to avoid the prematurity. In particular, the UWB rotationally symmetric sparse planar array synthesis problem is transformed into the sidelobe suppression problem of the array pattern at the highest frequency under the given array aperture, and the minimum spacing constraints is used to guarantee enough space to place physical UWB antenna elements. Two synthesis examples of UWB sparse planar arrays based on rotationally symmetric structures are presented. The results show that the peak sidelobe level (PSL) obtained by the proposed MDEA is significantly lower than the results obtained by some existing algorithms in an acceptable CPU time, which proves the effectiveness and superiority of the proposed MDEA.

An acoustic metasurface by applying planar periodic arrays of resonators with a multiple folded long neck for broadband sound absorption

An acoustic metasurface gives a broadband sound absorption by a planar periodic array combining small resonant modules tuned at different frequencies. The resonant module is often applied by a Helmholtz resonator, a membrane backed by an airtight cavity and a quarter wavelength closed tube, which have equivalent small area to a fraction of the wavelength. The author has studied the sound absorption of resonators by applying a multiple folded long neck and an airtight cavity for a thin sound-absorbing structure with high sound absorption at low frequencies below 100 Hz. In this paper, the author prototypes an acoustic metasurface by planar periodic array of Helmholtz resonators at various resonant frequency tuned by this neck and cavity of the resonator as a unit cell, and discusses the sound absorption characteristics. The prototyped acoustic metasurface gives a 40 % - 70 % sound absorption from 125 Hz to 250 Hz when it is combined with a 6.4 mm thickness of top plate including a 24 mm - 96 mm length of the multiple folded long neck and a 43.2 mm depth of the airtight cavity. And, more broadband sound absorption will be discussed by a theoretical analysis.

Sound absorption of resonators or perforated panels with multiple folded long tubes crammed in small module by additive manufacturing

Resonators or perforated panels give a large sound absorption at a resonant frequency tuned by opening area of the pores, neck length and a cavity depth behind the neck. The author has studied the sound absorption of thin tile-like resonators tuned at low frequencies by including a folded long neck in its surface panel. The resonators are made by an additive manufacturing with a fused deposition modeling (FDM). This paper makes the resonators or the perforated panels with multiple folded long tubes and discusses its measured sound absorption characteristics. One of the multiple folded long tubes is crammed in 12 mm × 12 mm × 19.2 mm of rectangular module even if the tube has 2 mm × 2 mm of opening area and 288 mm of length. A perforated panel consisted of planar periodic arrays of this module gives a large sound absorption at 69 Hz when a 40 mm depth of cavity behind the perforated panel. Furthermore, when the planar periodic arrays of small Helmholtz resonators applied single module and single cavity tuned at different resonant frequency, it has potential to form an acoustic metasurface with sound absorption at broadband frequencies.

Effect of masker selection schemes on the perceived affective quality of soundscapes: A pilot study

The perceived quality of a given soundscape may be improved by adding "pleasant" sounds via a speaker or electroacoustic system to the existing soundscape as maskers. Ideally, the choice of sounds should be automated to minimize the time and labor required to maintain such a system. Hence, we investigate the effect of several automated masker selection schemes on improving the ISO Pleasantness of urban soundscapes in a controlled laboratory environment. An ambisonic recording and 360-degree video of a location exposed to traffic noise was made and reproduced via a stacked planar speaker array and virtual reality headset. Simultaneously, maskers from a fixed candidate pool were overlaid on the reproduced soundscape in one of the following methods: random selection across the entire pool, fixed selection based on results in the literature, random selection across a restricted pool based on model-agnostic analysis of a pre-existing dataset, and random selection across a restricted pool based on a deep neural network trained on a pre-existing dataset. We also investigated a control condition with no added maskers, and evaluated the results based on changes in ISO Pleasantness ratings given by participants to the soundscape under each masker selection scheme, relative to the control condition.

Two-Dimensional Super-Resolution Direction-of-Arrival Estimation for Arbitrary Planar Array Geometries

The two-dimensional grid-free compressed sensing method with planar microphone arrays is expected to achieve super-resolution direction-of-arrival (DOA) estimation for acoustic sources in the hemispherical space in front of array. The existing methods are not yet well compatible with arbitrary planar array geometries. In this paper, we aim to break this limitation and explore a novel method applicable to arbitrary planar array geometries. First, the covariance between source-induced signals at arbitrary two microphones is formulated as related to the two-dimensional inverse Fourier transform of the source strength. Then, a mathematical model with a source sparsity constraint is built in the continuous domain to denoise the covariances of measured signals, which can be solved by decoupled positive semidefinite programming. Finally, the DOAs are extracted from the solution of the mathematical model via a matrix pencil and pairing method. Simulation and experimental results demonstrate the effectiveness of the proposed method.

A compressed sensing-based approach for null steering in partially adaptive planar arrays using a reduced number of adjustable array elements

This paper proposes two methods for multi-wide null steering in the beampattern of preconfigured partially adaptive planar array antennas using convex optimization and sparse recovery theory. The array elements are split into two categories. One of which is nonadjustable or has fixed excitations, and the other is adjustable. The weights of the adjustable part are perturbed to form wide nulls at the interference directions. In the first proposed method, all the adaptive array elements are used to steer the nulls. Here, convex optimization is used to obtain the required weight perturbations of all the adaptive elements. In addition to the constraints that are needed to impose the nulls, constraints were added to mitigate the pointing error and the lower peak-to-sidelobe ratio (PSLR) problems. In the second proposed method, the optimization problem is cast as a sparse recovery problem to reduce the number of elements to be perturbed from the set of adjustable elements only. The optimization problem is then relaxed to achieve a convex optimization problem and solved iteratively to cut down the number of radiating elements which needs to be perturbed from the set of adjustable elements. Simulations were conducted for different sizes of planar arrays up to a few hundred antennas and different configurations of adjustable elements. The results showed that changing the excitations of only 20-35% of the adjustable array elements is sufficient to steer the nulls without any pointing error or decrease in the PSLR. Also, the interference rejection ratio (IRR) achieved by the proposed methods is better than the minimum mean square error (MMSE) analytical solution.

Tunable and recoverable energy absorption of foam-embedded architected cellular composite material at multiple strain rates

Cellular multistable architected material has been widely studied for its promising energy absorption applications for personnel protection, protective packaging, and crash mitigation. Despite the tailorable properties enabled by their geometric features, a major issue in the actual application is their lower strengths in the elastic behavior of the multistable architected material. Herein, a novel design strategy of strain rate-dependent architected cellular composite material (FACCM) is proposed, aiming to achieve enhanced energy-absorbing properties with the proposed composite system than the single material constituent. Guided by numerical simulations and experimental tests, the compressive behaviour of FACCM at multiple strain rates and the effect of filled foam on it with specific geometric parameters are characterized. The quasi-static performances of the FACCM specimens were evaluated both at the cell level and planar array level. Our results indicate that the strength, stiffness, and snap-through behaviour of multistable architected material can be significantly improved by the filled foam at elevated loading rates regardless of quasi-static loading or impact tests. The current study offers a new strategy for developing novel packing, shock absorption, and impact protection systems.

Tailoring the dispersion characteristics in planar arrays of discrete and coalesced split ring resonators

In this report, the coupling and dispersion characteristics of discrete and coalesced square resonators was investigated in the MHz regime. Resonators with one and three gaps were considered. When the resonators are not in direct contact, the number of gaps has little effect upon the total coupling, which is negative. When the resonators are connected so that they share one side, the coupling can change drastically depending on the number of gaps. In particular, when the shared side has a gap, the total coupling coefficient switches to positive values, making it possible for forward travelling waves to propagate on arrays. Experimental, numerical and analytical data verify this behaviour.

Generation of highly azimuthal symmetric conical beam using the planar uniform circular array antenna for vehicular communication

Generation of highly azimuthal symmetric conical beam using the planar uniform circular array antenna for vehicular communication

Spatiotemporal analysis of 3D human iPSC-derived neural networks using a 3D multi-electrode array.

While there is a growing appreciation of three-dimensional (3D) neural tissues (i.e., hydrogel-based, organoids, and spheroids), shown to improve cellular health and network activity to mirror brain-like activity in vivo, functional assessment using current electrophysiology techniques (e.g., planar multi-electrode arrays or patch clamp) has been technically challenging and limited to surface measurements at the bottom or top of the 3D tissue. As next-generation MEAs, specifically 3D MEAs, are being developed to increase the spatial precision across all three dimensions (X, Y, Z), development of improved computational analytical tools to discern region-specific changes within the Z dimension of the 3D tissue is needed. In the present study, we introduce a novel computational analytical pipeline to analyze 3D neural network activity recorded from a "bottom-up" 3D MEA integrated with a 3D hydrogel-based tissue containing human iPSC-derived neurons and primary astrocytes. Over a period of ~6.5 weeks, we describe the development and maturation of 3D neural activity (i.e., features of spiking and bursting activity) within cross sections of the 3D tissue, based on the vertical position of the electrode on the 3D MEA probe, in addition to network activity (identified using synchrony analysis) within and between cross sections. Then, using the sequential addition of postsynaptic receptor antagonists, bicuculline (BIC), 2-amino-5-phosphonovaleric acid (AP-5), and 6-cyano-5-nitroquinoxaline-2,3-dione (CNQX), we demonstrate that networks within and between cross sections of the 3D hydrogel-based tissue show a preference for GABA and/or glutamate synaptic transmission, suggesting differences in the network composition throughout the neural tissue. The ability to monitor the functional dynamics of the entire 3D reconstructed neural tissue is a critical bottleneck; here we demonstrate a computational pipeline that can be implemented in studies to better interpret network activity within an engineered 3D neural tissue and have a better understanding of the modeled organ tissue.

Design of 1x5 Planar Array Microstrip Antenna with Edge Weighting to Increase Gain

Design of 1x5 Planar Array Microstrip Antenna with Edge Weighting to Increase Gain

Photonic beamforming using a quantum-dash optical frequency comb source.

We demonstrate photonic beamforming using a quantum-dash (QD) optical frequency comb (OFC) source. Thanks to the 25 GHz free spectral range (FSR) and up to 40 comb lines available from the QD OFC, we can implement phased antenna arrays (PAAs) with directional radiation and scanning. We consider two types of PAAs: a uniform linear array (ULA) and a uniform planar array (UPA). By selecting different comb lines with a programmable optical filter, we can tune the FSR of the OFC source and realize a discrete scanning function. We evaluate the beam squint of the ULAs, and the results show that we can achieve broadband operation. Finally, we show that we can achieve both directional radiation and scanning simultaneously using the UPA.

Cooperative concurrent targeting for planar arrays of point sources

Motivated by practical applications in satellite formations and directional antenna arrays, the problem of targeting a planar array of point sources at one common object of interest is proposed and then solved using novel distributed coordination strategies. These point sources are arbitrarily located on the x–y plane and the boundary point sources, whose either x or y coordinate is extremal, already orient to the non-coplanar target point. The only global information shared among the remaining point sources is the positive directions of the global coordinate axes x and y, and hence, they have to rely on sensing the changes of the orientation angles of their nearest neighbors to adjust their own orientation. We prove that under our control law, the orientation lines will asymptotically intersect at the same point of concurrency as the boundary point sources. The main idea behind the designed control law is the intuitive argument from Euclidean geometry that reducing the differences between the distances to the x–y plane of the pairwise intersection points of the orientation lines leads to realizing concurrent targeting. We further show the boundedness and exponential convergence speed of the orientation angles.