Planar Array Research Articles

Acoustic Forceps Based on Focused Acoustic Vortices with Different Topological Charges.

For enhanced energy concentration with improved flexibility for object manipulation, a focused acoustic vortex (FAV) is designed using a sector planar piston transducer array and acoustic lens that can produce the effective concentration of the acoustic field to perform the focusing function. Compared to the Gaussian beam, which tends to cause the object to deviate from the axis of acoustic propagation, FAVs can form a central valley region to firmly bind the objects, thus preventing off-target effects. The heat energy in the paraxial region is transferred to the vortex center in the form of heat transfer so that the temperature-sensitive liposomes captured can quickly release drugs, which has a good effect on targeted drug administration. The focused acoustic wave stopped acting on the tissue (gel) for 2 s, the temperature of the vortex center continued to rise, reaching 41.5 °C at the moment of 3.7 s, at which point the liposomes began to release the drug. The FAVs capture the drug and use its thermal effect to achieve accurate and rapid treatment. The simulation results show that the drug release temperature of temperature-sensitive liposomes can be achieved by controlling the action time of the vortices. This study provides a reliable theoretical basis for the clinical application of targeted drugs.

Construction of DNA Bilayer Tiles and Arrays Using Circular DNA Molecules as Scaffolds.

Using oligonucleotides to weave 2D tiles such as double crossovers (DX) and multi-arm junction (mAJ) tiles and arrays is well-known, but weaving 3D tiles is rare. Here, we report the construction of two new bilayer tiles in high yield using small circular 84mer oligonucleotides as scaffolds. Further, we designed five E-tiling approaches to construct porous nanotubes of microns long in medium yield via solution assembly and densely covered planar microscale arrays via surface-mediated assembly.

A Novel THz Massive MIMO Beam Domain Channel Model for 6G Wireless Communication Systems

In this paper, a three dimensional (3D) geometry based stochastic model (GBSM) considering planar antenna array is firstly proposed for the sixth generation (6 G) terahertz (THz) massive multiple-input multiple-output (MIMO) wireless communication systems. Then, a novel beam domain channel model (BDCM) is derived from the proposed GBSM based on the Fourier transform matrix from the spatial domain to the angle domain in horizontal and vertical directions simultaneously. The THz propagation characteristics, including non-negligible diffuse scattering and limited order of reflection, are considered in these two channel models. In addition, the proposed GBSM and BDCM can capture the spherical wavefront and spatial non-stationarity characteristics in massive MIMO channels by deriving steering vectors of near-field clusters and partly visible clusters, respectively. The angle-domain sparsity property of the BDCM can be observed, which helps reduce the complexity of the GBSM and improve the mathematical tractability. Typical statistical properties of the proposed GBSM and BDCM are derived and compared. The effects of the spherical wavefront on space-time-frequency correlation functions (STF-CFs) and channel capacity are also studied for the proposed GBSM and BDCM. The power leakage of the BDCM caused by the spherical wavefront and visible region (VR) is thoroughly analyzed. It is found that the statistical properties of the GBSM and BDCM fit well and are considerably influenced by the spherical wavefront and VRs.

An Efficient Bias Correction Method for Large Planar Polarimetric Phased Array Radar

For a large planar polarimetric phased array radar, a bias correction matrix obtained from array pattern measurements needs to be applied when the beam is pointed off broadside. To avoid measuring all possible beam directions while ensuring the correction accuracy, an efficient bias correction method using polynomial surface fitting is proposed. After dividing the entire scan area into several subregions, merely dozens of beam directions are measured in each subregion. Through the polynomial surface model, the correction matrices of unmeasured beam directions can be well predicted. The simulated results show that the proposed method can effectively achieve accurate bias correction in two-dimension <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pm 45^{\circ }$</tex-math></inline-formula> scanning. Under the same relative error level for antenna pattern measurement, the results of Monte Carlo simulations verify that the proposed method has a more stable performance than directly beam-by-beam measurement due to its least square process.

Synthesis of Large Ultrawideband Sparse Planar Arrays by Utilizing a Cooperative Coevolutionary Iterative Fourier Transform

This letter introduces a cooperative coevolutionary iterative Fourier transform (CCIFT) technique to extend the conventional IFT to large ultra-wideband (UWB) sparse planar array synthesis. In the proposed CCIFT, a dense initial element position grid such as a spacing of half a wavelength at the highest frequency is adopted to avoid the presence of grating lobes at high frequency band, and a probability-assisted element selection mechanism is presented to guarantee the obtained array layout to meet a preset minimum spacing constraint, enabling the placement of physical UWB antenna elements. In addition, a cooperative coevolutionary strategy is presented to avoid prematurity by establishing the information interaction between different excitation distributions from multiple parallel IFT procedures. Two examples are conducted and results show that the CCIFT can achieve a considerably lower peak sidelobe level (PSL) than some state-of-art algorithms within an acceptable CPU time, which demonstrates its effectiveness and superiority.

Effect of Parasitic Patch for the Radiation Characteristics Microstrip Antenna Planar Array with Distribution Edge

Effect of Parasitic Patch for the Radiation Characteristics Microstrip Antenna Planar Array with Distribution Edge

Enhanced Effective Aperture Distribution Function for Characterizing Large-Scale Antenna Arrays

Accurate characterization of large-scale antenna arrays is growing in importance and complexity for the fifth-generation (5G) and beyond systems, as they feature more antenna elements and require increased overall performance. The full 3D patterns of all antenna elements in the array need to be characterized because they are in general different due to construction inaccuracy, coupling, antenna array's asymmetry, etc. The effective aperture distribution function (EADF) can provide an analytic description of an antenna array based on a full-sphere measurement of the array in an anechoic chamber. However, as the array aperture increases, denser spatial samples are needed for EADF due to large distance offsets of array elements from the reference point in the anechoic chamber, leading to a prohibitive measurement time and increased complexity of EADF. In this paper, we present the EADF applied to large-scale arrays and highlight issues caused by the large array aperture. To overcome the issues, an enhanced EADF is proposed with a low complexity that is intrinsically determined by the characteristic of each array element rather than the array aperture. The enhanced EADF is validated using experimental measurements conducted at 27-30 GHz frequency band with a relatively large planar array.

Optimized Design for IRS-Assisted Integrated Sensing and Communication Systems in Clutter Environments

In this paper, we investigate an intelligent reflecting surface (IRS)-assisted integrated sensing and communication (ISAC) system design in a clutter environment. Assisted by an IRS equipped with a uniform planar array (UPA), a multi-antenna base station (BS) is targeted for simultaneously sensing multiple targets in the non-light-of-sight (NLoS) region and communicating with multiple communication users (CUs). We consider the joint IRS-assisted ISAC design in the case with Type-I or Type-II CUs, where each Type-I CU and Type-II CU can and cannot cancel the interference from sensing signals, respectively. Under the perfect communication/sensing channel state information assumption, we aim to maximize the minimum sensing beampattern gain among multiple targets, where the sensing beampattern gain qualifies the achieved illumination signal power at the given location of the target of interest. We jointly optimize the BS’s communication-sensing beamformers and the IRS’s phase shifting matrix, subject to the signal-to-interference-plus-noise ratio (SINR) constraint for each Type-I/Type-II CU, the interference power constraint per clutter, the transmission power constraint at the BS, and the cross-correlation pattern constraint. Due to the design variable coupling, the joint IRS-assisted ISAC design problem is shown to be non-convex in the case with Type-I or Type-II CUs. To circumvent the non-convexity dilemma, we propose semidefinite relaxation (SDR) based alternating optimization algorithms in both cases, for which the computational complexity and convergency behavior are analyzed. In the case with Type-I CUs, we show that the dedicated sensing signal at the BS can help enhance the sensing performance gain. By contrast, the dedicated sensing signal at the BS is not required for the IRS-assisted ISAC designs in the case with Type-II CUs. Numerical results are provided to show that the proposed IRS-assisted ISAC design schemes achieve a significant gain over the existing benchmark schemes.

Chasing the bird: 3D acoustic tracking of aerial flight displays with a minimal planar microphone array

ABSTRACT Tracking the flight patterns of birds and bats in three-dimensional space is central to key questions in evolutionary ecology but remains a difficult technical challenge. For example, complex aerial flight displays are common among birds breeding in open habitats, but information on flight performance is limited. Here, we demonstrate the feasibility of using a large ground-based 4-microphone planar array to track the aerial flight displays of the cryptic Jack Snipe Lymnocryptes minimus. The main element of male display flights resembles a galloping horse at a distance. Under conditions of sufficient signal-to-noise ratio and of vertical alignment with the microphone array, we successfully tracked male snipe in 3D space for up to 25 seconds with a total flight path of 280 m. The ’gallop’ phase of male snipe dropped from ca. 141 to 64 m above ground at an average velocity of 77 km/h and up to 92 km/h. Our project is one of the first applications of bioacoustics to measure 3D flight paths of birds under field conditions, and our results were consistent with our visual observations. Our microphone array and post-processing workflow provides a standardised protocol that could be used to collect comparative data on birds with complex aerial flight displays.

Three-Dimensional Motion Compensation Method Based on Sparse Array Designed for Time-Division Multiplexing Multiple-Input-Multiple-Output Through-Wall Radar

A large-aperture radar composed of a multiple-input-multiple-output (MIMO) planar array can complete 3D through-wall imaging (TWI), but the simultaneous work of the multiple transceiver channels leads to difficulties in designing the hardware. In engineering, multiple transceiver channels are usually realized by time-division multiplexing (TDM) in MIMO radar, which is called TDM MIMO radar. A time delay will be introduced when the channels are switched, which will cause high sidelobes and position deviation in the 3D imaging of moving targets, also known as range migration. This paper proposes a motion compensation algorithm based on sparse array, designed to eliminate range migration in moving targets in 3D TWI scenes. In the proposed algorithm, the coincident array elements of the equivalent array are used as the compensation channels to calculate the position difference of the target, which can correct the remaining MIMO channels. The proposed algorithm is compared with no compensation, and the reference-channel-based motion compensation algorithm (RCMCA). According to the simulation and experimental results, the proposed motion compensation algorithm can effectively eliminate sidelobes, and keep the position deviation within 0.30 m in the 3D TWI of moving targets under the TDM MIMO radar, without increasing the system complexity.

Electrochemical Properties of Sputtered Ruthenium Oxide Neural Stimulation and Recording Electrodes

A chronically stable electrode material with a low impedance for recording neural activity, and a high charge-injection capacity for functional electro-stimulation is desirable for the fabrication of implantable microelectrode arrays that aim to restore impaired or lost neurological functions in humans. For this purpose, we have investigated the electrochemical properties of sputtered ruthenium oxide (RuOx) electrode coatings deposited on planar microelectrode arrays, using an inorganic model of interstitial fluid (model-ISF) at 37 °C as the electrolyte. Through a combination of cyclic voltammetry (CV) and an electrochemical impedance spectroscopy (EIS) modelling study, we have established the contribution of the faradaic reaction as the major charge-injection contributor within the safe neural stimulation potential window of ±0.6 V vs. Ag|AgCl. We have also established the reversibility of the charge-injection process for sputtered RuOx film, by applying constant charge-per-phase current stimulations at different pulse widths, and by comparing the magnitudes of the leading and trailing access voltages during voltage transient measurements. Finally, the impedance of the sputtered RuOx film was found to be reasonably comparable in both its oxidized and reduced states, although the electronic contribution from the capacitive double-layer was found to be slightly higher for the completely oxidized film around 0.6 V than for its reduced counterpart around −0.6 V.

Joint frequency space design approach for efficient planar frequency diverse arrays

Antenna arrays offer advantages in terms of spatial diversity, allowing for control over pattern specifications in space. The incorporation of frequency diversity in arrays presents an opportunity to manipulate beams in the Space–Time domain. Unlike conventional arrays, Frequency Diverse Arrays (FDA) with added frequency diversity exhibit time-variant and range-dependent patterns. These time variations impact both steering and auto-scanning applications. The array factor is influenced by the coherent interplay between frequency and spatial distributions of elements, thereby correlating the spatial and temporal behavior of the FDA’s pattern. To address this space-frequency coherency, an adjoint spatial-frequency design algorithm is the most effective approach to controlling the array's spatial and temporal behavior. Given the complexity of the array factor formulations in FDAs, elements' frequency and spatial distribution have traditionally been designed separately. However, this study proposes an algorithm that simultaneously allocates the location and frequency of elements to achieve a desired pattern. Symmetrical FDA is initially designed using a straightforward formulation of the array factor obtained through symmetry, ensuring a stable and periodic scanning beam. Subsequently, two important design parameters and several crucial design criteria for scanning applications are suggested by analyzing the formulations. These parameters form the basis of a designing algorithm that enables the simultaneous design of element location and frequency in the space-frequency plan, thus meeting the temporal and spatial requirements of the pattern. To demonstrate the efficacy of the proposed algorithm, two different planar arrays are designed, and their results are compared with those of other planar configurations. This study lays the foundation for a novel approach to designing Frequency Diverse Arrays (FDAs), opening up new possibilities in array design.

High-Conductivity MXene Film-Based Millimeter Wave Antenna for 5G Applications

Millimeter wave antennas have the advantage of high directivity, miniaturization, high resolution and data transfer speed, wide bandwidth, and lower latency. In this work, a millimeter wave planar array antenna (PAA) with the characteristics of wideband and low sidelobes, which consists of eight identical linear array antenna (LAA) based on Ti3C2 MXene, is designed and fabricated. It is the first time that MXene antennas are proposed for a 5G millimeter wave antenna application. MXene PAA has a high realized gain of 22.22 dBi and a −10 dB impedance bandwidth of measurement covering the range from 24 GHz to 28 GHz, including the 5G FR2—n258 frequency band. With Chebyshev current distribution, the MXene PAA has a half-power beam width of 10.2° and 10.8° in the xoz-plane and yoz-plane radiation patterns with the sidelobes levels below −20 dB, respectively. Therefore, MXene PAA is suitable for 5G mobile communication applications.

Fully-Metallic Additively Manufactured Monolithic Double-Ridged Waveguide Rotman Lens in the K/Ka-Band.

This paper reports on the design and experimental validation of a fully-metallic double-ridged waveguide 10 × 10 Rotman lens additively manufactured as a single part. The wide band operation of this quasi-optical beamformer enables us to cover the uplink and downlink frequencies allocated to satellite communications in the K/Ka-band, from 17.3 GHz to 30 GHz. The feeding port design was adjusted to enable vertical printing, thus minimizing the use of supporting structures. A prototype was manufactured and tested. The reported results indicate losses in the range of 0.5 dB in the lower-frequency band and 0.8 dB in the upper-frequency band, including the waveguide transitions added for test purposes. The measured reflection and coupling coefficients remain below -11.5 dB over the operating band. The standard deviation of the residual phase error across the array ports is below 5° in simulation and below 10° in measurements. Array factors synthesized using the scattering parameters confirm the good stability of the beamforming functionality over the wide frequency band analyzed. This monolithic design is a promising step toward more integrated antenna systems, such as a compact dual-stack configuration for planar array design.

Linear Antenna Array Sectorized Beam Scanning Approaches Using Element Position Perturbation in the Azimuth Plane.

In this paper, two sector beam scanning approaches (BSAs) based on element position perturbations (EPPs) in the azimuth plane are introduced. In EPP-BSA, the elements' excitations are kept constant and the elements' positions in the direction normal to the array line are changed according to a predetermined EPP pattern. The magnitude and repetition rate of the selected EPP pattern determines the steering angle of the main beam. However, EPP-BSA results in a wide scanning range with a significant increase in the side lobe level (SLL). To mitigate this drawback, a reduction in the SLL of the array pattern is firstly performed using the single convolution/genetic algorithm (SC/GA) technique and then perturbing the elements' positions in the azimuth plane. This combination between SLL reduction and EPP-BSA (SLL/EPP-BSA) results in a smaller scanning range with a relatively constant half power beamwidth (HPBW) and a much lower SLL. In addition, keeping the synthesized excitation coefficients constant without adding progressive phase shifters facilitates the manufacturing process and reduces the cost of the feeding network. Furthermore, a planar antenna array thinning approach is proposed to realize the EPP-BSA. The results are realized using the computer simulation technology (CST) microwave studio software package, which provides users with an optimized modeling environment and results in realizable and realistic designs.

Sparse Tiled Planar Array: The Shared Multibeam Aperture for Millimeter-Wave Joint Communication and Sensing

Multibeam planar arrays are investigated as shared apertures for dual functionality in millimeter-wave (mmWave) joint communication and sensing (JCAS), providing time division duplex communication and full-duplex sensing with steerable beams. The conventional uniform planar arrays (CUPA)s have limited angular resolution, whereas the sparse planar arrays (SPA)s are often very costly to implement. In order to have a low-cost aperture with high angular resolution, we propose to design a sparse tiled planar array (STPA) shared aperture. Our proposed solution is modular tiling and uniform at the subarray level but sparse at the aperture level. The modular tiling and sparse design of a planar array are non-convex optimization problems; however, we exploit the fact that the more irregularity of the antenna array geometry, the less the side lobe level (SLL). In a JCAS scenario, we compare the performance of STPA, CUPA. and SPA, regarding the spectral efficiency of a line-of-sight (LoS) included communication link, detection loss rate, and detection accuracy rate for sensing, and the blockage time in case of an overlapping communication and sensing beam. The SPA for comparison has the same size and beamwidth as STPA, but less average SLL and less modular design. The results show that the same spectral efficiency is achieved in the communication link for CUPA, SPA, and STPA. The effect of a smaller beamwidth of the STPA and SPA is reflected in the lower detection loss rate of them compared to that of the CUPA, but the side lobes of these sparse solutions result in errors in the association of the detected and true targets and hence a reduction in the detection accuracy. In such a multibeam solution for JCAS, it is critical to study blockage time, and we show that the STPA and SPA have a 40% shorter blockage time compared to the CUPA when a blocker moves across the LoS of the communication link. Therefore, STPA is a trade-off solution between CUPA and SPA, since it has uniformly distributed antennas within the subarrays as in CUPA, but a sparse solution in the whole aperture as in SPA, which guarantees the same beamwidth and sensing performances as a SPA.

A circularly polarized phased array antenna with 60° scanning in the D-plane using a top-loaded patch

The requirements for circularly polarized (CP) phased array antennas are growing with the rapid development of electronic systems. To achieve a low-profile, wideband, and large scanning-angle CP, we constructed a novel CP unit cell with a two-layer folded coupling patch and a top-loaded patch. The design of the folded coupling patch was based on the principle of reverse current cancellation. Compared with the single-layer coupling patch, the folded coupling patch suppressed the occurrence of strong in-band resonance and obtained a wider axial ratio (AR) bandwidth. To solve the problem of AR performance deterioration in the D-plane scanning, we introduced the top-loaded patch to replace the thick wide-angle impedance matching layer, which improved the difference in co-polarization components and reduced cross-polarization level. Thus, a large scanning angle of more than 60° in the D-plane was obtained. An 8 × 8 planar array based on the proposed CP unit cell was designed. The array achieved a 3.9:1 (3.2–12.5 GHz) AR bandwidth and up to 60° scanning angle in the D-plane and 70° in the E-/H-plane; an AR smaller than 3 dB was demonstrated over the entire scanning range.

Peculiarities of adaptive signal processing in circular antenna arrays

Formulation of the problem. Today, antenna arrays are often used as directional antennas of different radio systems. The main advantages of the such antennas over the mechanically steered directional antennas are the ability to steer the main lobe (beam) of the Radiation Pattern (RP) without the rotation of the array, and also the ability to control the shape of the RP. However, the antenna arrays also have some drawbacks. For example, a drawback of the linear and the planar antenna arrays is the varying beamwidth. This width increases as the orientation of the beam moves from the normal to the aperture to the plane of the aperture. This feature is due to the fact that when the beam is deflected, the effective aperture of the antenna array decreases, and this is the reason of the beam increase. If it is required to steer the beam in a wide range of angles while maintaining its width, then this restricts the usage of a linear and flat antenna arrays as the directional antennas. This disadvantage is practically absent in the circular antenna arrays. Therefore, such arrays are attractive for the usage, for example, in the radio communication systems, because they allow the beam to move within 360° in azimuth plane while maintaining its width practically fixed. If the antenna array is built using a digital beamforming architecture (digital array), then such an array can also be easily made as a multi-beam one, that will provide a parallel view of space. In multibeam digital antenna arrays, the same analog portion of each channel from the antenna to the digital output is used to form all the beams. And only in digital form, the separate devices for the forming of these beams are required, which multiply the channel output signal samples by the weights and add the weighted signals together to form the output signals of the antenna array. The access to the signals from the outputs also allows such an antenna array to easily become adaptive, because these signals are used to calculate the weights in all the adaptive algorithms. The adaptive signal processing allows to suppress the interferences. The suppression of the interference signals in the output signal of the antenna array is achieved due to the creation of the dips (low levels) in the RP towards the sources of these interferences. Such a change in the shape of the RP is provided by the changing weights calculated using an adaptive algorithm. Target. The paper deals with the circular adaptive antenna arrays with digital beamforming. The features of the such adaptive antenna arrays and their performance are considered. Results. The architecture of a single beam and a multibeam adaptive antenna array is considered, as well as a procedure (algorithm) for the calculation of its weights. It is also demonstrated the efficiency of a circular adaptive antenna array in terms of maintaining its beamwidth regardless of its direction and simultaneously suppressing interferences, that practically does not affect this beamwidth. Practical significance. The considered adaptive antenna array can be used as a directional antenna in radio systems where it is required to form a several beams simultaneously, to maintain their width regardless of steering directions, and also to suppress the interference signals in the output signal.

Millimeter-Wave Imaging via Circular-Arc MIMO Arrays

Millimeter-wave (MMW) imaging has a promising prospect in application of concealed weapons detection. To that end, we propose a circular-arc multiple-input–multiple-output (MIMO) array scheme with uniformly spaced transmit and receive antennas along the horizontal-arc direction while scanning along the vertical direction. The antenna beams of the circular-arc MIMO array can provide more uniform coverage of the imaging scene than those of linear or planar MIMO arrays, which is especially important for the detection of concealed weapons carried by personnel. Furthermore, a near-field 3-D imaging technique, based on spatial frequency-domain processing, is presented together with a detailed analysis of sampling criteria and resolutions. Numerical and experimental results are provided to demonstrate the performance of the proposed method in comparison with those of the currently most used array schemes and imaging algorithms.

Irregular Modular Subarrayed Phased Array Tiling by Algorithm X and Differential Evolution Algorithm

In this letter, an efficient and versatile method based on algorithm X and differential evolution algorithm is proposed to synthesize irregular modular subarrayed planar phased arrays with exact tiling. To alleviate the time-consuming problem of using algorithm X to synthesize large arrays, the proposed method obtains the subarray configuration with exact tiling through twice-partitioning operations. In the first partition process, the planar phased array is divided into several first-level subarrays. In the second partition process, the first-level subarrays are respectively divided into pre-specified irregular modular subarrays, called second-level subarrays. All feasible schemes for dividing the first-level subarrays and second-level subarrays can be obtained by algorithm X. Through the above partition process, the partitioning paradigm can be represented by only a few variables, which can be optimized by swarm intelligence algorithms. In this letter, the variables representing the subarray configuration are optimized by differential evolution algorithm to obtain excellent radiation performances. Three representative numerical examples are presented and discussed to assess the validity, efficiency, and reliability of the proposed method.