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The space-time adaptive processing (STAP) technique has achieved good clutter suppression performance for a side-looking airborne radar; however, it suffers from severe performance degradation in nonside-looking airborne radar. This is because the clutter distribution varies considerably with range. The 3D STAP can provide better performance compared with the traditional STAP methods in such a nonstationary clutter environment, but it requires high computational complexity and sample support. In this letter, the characteristic of azimuth-elevation-Doppler 3-D beam pattern for the planar array is explored, and a novel reduced-dimension scheme combined with this characteristic is proposed. We further developed three basic reduced-dimension structures according to this scheme. Furthermore, we also prove that the first and third structures are just the direct extension of the traditional 2-D generalized multibeam and joint-domain localized methods. The second one is an original structure that performs local reduced-dimension processing with three orthogonal planar windows. Numerical results verify that the proposed structures have significant advantages in reducing computational load and training sample numbers compared with existing 3D STAP methods. In particular, the second structure shows the best comprehensive performance in the bad samples environment.

Mobile wireless data collection in beyond 5G (B5G)/6G cellular internet of things (IoT) networks can be achieved by unmanned aerial vehicle (UAV) with high flexible mobility and low cost. In this paper, a half-duplex UAV relay is exploited to improve the achievable rate of downlink millimeter-wave (mmWave) massive multi-user multiple-input and multiple-output (MU-MIMO) networks. To improve the spectrum efficiency and mitigate the inter-beam interference, the hybrid beamforming (HB) designs of the base station (BS), the UAV and multiusers are taken into account simultaneously. To maximize the achievable rate from the BS to the multiusers, a two-stage design approach which tries to design the two stages jointly by avoiding the loss of information is proposed. Assuming multiusers are alignment in different beams, the strong effective channel-based non-orthogonal multiple access (NOMA) in the power domain is employed to assign power efficiently for each user, thereby increasing the number of users. Simulation results validate the proposed HB-NOMA approach can achieve good achievable rate performance in both uniform linear array and uniform planar array.

In this work, a hybrid architecture called fully connected sub-array (FCSA) is considered for uplink data decoding with mutual coupling and space constraints at the base station (BS). The above architecture achieves the same system performance with a lower hardware complexity than a fully connected array. The packing of many antenna elements on a small surface area leads to the mutual coupling effect. Moreover, having antenna elements at the BS with finite directivity is more practical than having isotropic antenna elements at the BS. In the present work, we have considered uplink data decoding with dipole antennas arranged in a uniform planar array (UPA) grid at the BS with the error in separation between the antenna elements and mutual coupling as additional impairments. An approximate expression for the mutual coupling matrix (MCM) is derived and verified. A geometry-based stochastic model (GBSM) for the channel is considered between the user equipment (UE) and the BS. The performance of the hybrid architecture in terms of spectral efficiency (SE) and bit error rate (BER) of the system, with the mutual coupling effect and antenna separation error, is analyzed. Numerical simulations show that when the BS has no information on the MCM, SE and the system's BER performances with the FCSA architecture degrade. In the absence of any information on the coupling effect, the system performs better when a more extensive array size is used at the BS. Both the SE and BER degraded when longer dipoles were used in the array.

A compact wideband and wide-scanning planar triangular-lattice phased array is proposed. The proposed element is a U-slot microstrip antenna surrounded by a substrate-integrated cavity (SIC) structure fed by a 50 $\Omega$ coaxial cable. The scan blindness is effectively shifted out of the operation band as the SIC structure obstructs the surface wave and mutual coupling. The proposed array is arranged in a triangular lattice with fewer elements than a rectangular one. A $4\times 8$ planar array prototype is fabricated and measured over $X$ -band. The antenna provides a bandwidth of over 30% frequency range under ±60° scanning in all azimuth planes.

Modern synthetic aperture radar (SAR) systems for Earth observation from space employ innovative hardware concepts. The key idea is to digitize the output of a multielement antenna almost immediately after the receiver and to dynamically process these data either onboard the radar satellite in real time or on the ground. This article addresses the performance of such digital beamforming (DBF) systems in the presence of phase and magnitude errors in the digital channels. For this, analytic expressions for the sensitivity and range ambiguity performance are derived. These equations are kept general so that they are valid for both planar array antennas and array-fed reflector antennas. It is an important objective of this article to compare these two antenna types to each other. A major conclusion from this analysis is that direct-radiating phased arrays are inherently more susceptible to random phase and magnitude errors compared with array-fed reflector antenna-based systems. This manifests itself in a more rapid degradation of the imaging performance with phased array antennas.

This article presents the 38-GHz phased array 32-element Tx and 16-element Rx with 2-GHz IF and 5-GHz LO for fifth-generation (5G) millimeter-wave (MMW) communications. The Tx and Rx beamformers and upconverters/downconverters are fabricated in 65-nm CMOS. The PAs and LNAs near antenna ends are fabricated in 0.15- $\mu \text{m}$ GaAs pHEMT. The eight-element Tx and four-element Rx phased array printed circuit board (PCB) modules integrated with multiple integrated circuits (ICs) and endfire antennas are implemented as unit cells. Four pieces of Tx modules are vertically stacked to construct an $8\times {4}$ brick array (planar array), while four Rx modules are to construct a $4\times {4}$ array. According to 38-GHz over-the-air (OTA) measurements, the 32-element Tx shows 47.5-dBm equivalent isotropic radiated power (EIRP) at OP $_{\mathrm {1 ~dB}}$ with −35.2-dB image rejection ratio (IMRR) and −37.4-dB $\times 8$ LORR. The 16-element Rx at 38 GHz shows −4-dBm OP $_{\mathrm {1~dB}}$ with −28-dB IMRR and −36.6-dB LORR. The Tx and Rx support the beam scanning around ±60° azimuth and ±30° elevation planes. The Tx-to-Rx wireless data link demonstrates 64 quadrature amplitude modulation (QAM)/400 M-BR, 256 QAM/200 M-BR, and 512 QAM/100 M-BR in 20 m. To the best of our knowledge, this work is the first 5G 37-/39-GHz phased array Tx/Rx using the scalable brick array configuration and demonstrating competitive performances compared with previous works.

Radar images of humans and other concealed objects are considerably distorted by attenuation, refraction and multipath clutter in indoor through-wall environments. While several methods have been proposed for removing target independent static and dynamic clutter, there still remain considerable challenges in mitigating target dependent clutter especially when the knowledge of the exact propagation characteristics or analytical framework is unavailable. In this work we focus on mitigating wall effects using a machine learning based solution -- denoising autoencoders -- that does not require prior information of the wall parameters or room geometry. Instead, the method relies on the availability of a large volume of training radar images gathered in through-wall conditions and the corresponding clean images captured in line-of-sight conditions. During the training phase, the autoencoder learns how to denoise the corrupted through-wall images in order to resemble the free space images. We have validated the performance of the proposed solution for both static and dynamic human subjects. The frontal radar images of static targets are obtained by processing wideband planar array measurement data with two-dimensional array and range processing. The frontal radar images of dynamic targets are simulated using narrowband planar array data processed with two-dimensional array and Doppler processing. In both simulation and measurement processes, we incorporate considerable diversity in the target and propagation conditions. Our experimental results, from both simulation and measurement data, show that the denoised images are considerably more similar to the free-space images when compared to the original through-wall images.

In this article, a two-dimensional (2-D) Luneburg lens-based beamforming network (LL-BFN) realizable on parallel-plate-sandwiched substrates is implemented to excite a planar phased array of antennas for near-field focus (NFF) applications of multibeam radiations. The concept is to select a proper position of a cylindrical ring surrounding the 2-D Luneburg lens and intercept the phases on this ring to excite the antenna array for NFF multibeam radiations. The intercepted phases are consistent to that required to excite a planar array for NFF radiation. Due to the circular symmetry characteristics of LL-BFN architecture, the distribution of the resulted multibeams exhibits a spatial shift of focal points when the lens is excited by angularly shifted ports on the LL-BFN. The concept is developed with both the numerical and experimental results shown to validate the feasibility of LL-BFN architecture. Practical implementation of low cost is demonstrated.

Compared with conventional two-dimensional space-time adaptive processing (2D-STAP) methods, the elevation-azimuth-Doppler three-dimensional space-time adaptive processing (3D-STAP) method has the advantage of suppressing nonstationary clutter. Thereby, it is suitable for nonsidelooking airborne radar (non-SLAR) applications. However, its huge training data requirements and computational load are often beyond radar's ability in practical clutter environments. In this correspondence, we develop a simple but efficient reduced-degree-of-freedom (DOF) 3D-STAP method that significantly reduces the required training data and the computational complexity while maintaining the suboptimal clutter suppression performance. The proposed method transforms the planar array data into linear array data in azimuth and in elevation, respectively, thereby beamforming an equivalent cross-shape array prior to STAP. In consequence, only a few spatial DOFs, including azimuth and elevation dimension, are used for STAP directly resulting in the potential advantage for nonstationary clutter suppression and drastically reducing training data requirements and computational load. Furthermore, the clutter rank estimation rules of the planar array and the transformed cross-shape array are derived, and the required elevation DOFs of the proposed method are further discussed in detail. Simulations for clutter suppression of non-SLAR show that the proposed STAP method outperforms the state-of-the-art 3D-STAP method in terms of convergence and computational complexity.

A fast method of transmit beamforming for large planar Multiple-input multiple-output (MIMO) radar is proposed. For MIMO radar with large elements, it is difficult to design a large number of orthogonal waveforms. We design a weight matrix to connect orthogonal waveforms and array elements. We optimize the weight matrix such that the transmit beampattern approximates the desired transmit beampattern. By introducing an auxiliary variable, a cyclic optimization algorithm based on Fast fourier transform (FFT) is proposed to obtain the optimal weight matrix, which is very efficient and can satisfy the real-time requirements. Numerical examples are provided to verify the effectiveness of the proposed algorithm.

Polarized smart antenna array has attracted considerable interest due to its capacity of matched reception or interference suppression for active sensing systems. Existing literature does not take full advantage of the combination of polarization isolation and smart antennas and only focuses on uniform linear array (ULA). In this paper, an innovative synthesis two-dimensional beampattern method with a null that has cross-polarization for polarized planar arrays is proposed in the first stage. This method aims to further enhance the capability of interference suppression whose optimization problem can be solved by second-order conic programming. In the second stage, a new sparse array-optimized method for the polarized antenna array is proposed to reduce the high cost caused by the planar array that is composed of polarized dipole antennas. Numerical examples are provided to demonstrate the advantages of the proposed approach over state-of-the-art methods.

We propose a compact circularly polarized series-fed patch array with enhanced radiation performance at $S$ -band. To our best knowledge, no similar single-layer structure has been designed, measured, and reported in the literature with equivalent radiation performances in terms of reduced sidelobe level (SLL) and aperture efficiency as well as compactness and simplicity. The planar array consists of a 50- $\Omega $ microstrip single feed point, offering uniform and efficient excitation of all its elements that enable a broadside beam with high-gain and low sidelobes. A feeding network for such aperture control is designed and optimized to provide good impedance matching with a two-point excitation per radiating element, which is based on 0° and 90° meander lines to enable circularly polarized radiation. A structure made by a $4\!\!\times \!\!1$ arrangement of square patches is simulated, optimized, and manufactured, providing a realized gain of about 10 dBic and an SLL below −15 dB. Very good axial ratios and high efficiencies are obtained. The proposed antenna may be of interest for next-generation far-field wireless power transmission systems and other applications including target tracking, radar, and internet of things technologies requiring efficient circularly polarized radiation.

Due to the range-angle-dependent beampattern, frequency diverse array (FDA), either in the form of linear array or planar array, has been extensively investigated in recent years. However, the conformal FDA is seldom studied. In this article, a general conformal FDA framework is first developed. Specifically, a hemi-spherical FDA is exploited to illustrate the unique advantage of conformal FDA in terms of the 3-D localization ability. Furthermore, to deal with the intrinsic defect of time-variant range–angle-coupled beampattern of the FDA, an optimized static nonlinear frequency offset (OSNFO) is proposed. The OSNFO not only decouples the conformal FDA beampattern in the range–angle dimension, but also copes with its inherent time-variant problem, resulting in a quasi-time-invariant 3-D focusing beampattern. Numerous simulation results have been provided to demonstrate the superiority and the effectiveness of the OSNFO-conformal FDA.

The four-channel monopulse (FCM) technique enables a phased array radar (PAR) to track the angular location of two targets with reduced complexity and thus has been extensively investigated in the fields of radar multitarget tracking. However, the FCM technique has limited practical use because it was originally designed for a four-channel monopulse radar and is suitable only for a PAR configured with a rectangular planar array. In addition, the FCM technique is unable to resolve two targets when they have identical azimuthal or elevation angles due to angular ambiguity. In this paper, we propose a subarray-based FCM (SFCM) method to achieve an efficient, unambiguous, and fast two-target resolution, which is applicable to a PAR with a regular shape, i.e., circular arrays, elliptical arrays, and regular-octagonal arrays. Specifically, the proposed SFCM method consists of two stages: coarse estimation and precise estimation. Coarse estimation is performed by an inscribed rectangular array to initially estimate the angles of the two targets, and then precise estimation is achieved by a closed-form solution. Moreover, the proposed SFCM method can avoid the angular ambiguity issue via coordinate rotation. Furthermore, we prove that the optimal rotation angle is $45^\circ$ for minimizing the estimation error. In the performance analysis, we evaluate the effectiveness, computational complexity and Doppler effect for the SFCM method. Numerical results demonstrate that the proposed method outperforms its counterpart FCM method in accuracy, applicability, and robustness.

Electrically conformal antenna arrays (ECAA) for 2-dimensional (2-D) beamforming configured by wide beamwidth multipole radiation elements are proposed. Unlike the conventional conformal antenna array with physically curved shape, the proposed arrays are planar structures with wide-angle beam steering. The wide range of beam steering with a low gain variation allows the planar array structure to achieve the electrically conformal phased array patterns. In order to verify the ECAA concept, two different types of ECAA in a 1 × 8 configuration using planar multipole antenna elements were fabricated at 5.8 GHz and compared to the conventional patch array. Each multipole element had half-power-beamwidth (HPBW) wider than 110° at both E- and H-planes with the maximum HPBW of 175°. The first type of ECAA showed a measured peak gain of 10.8 dBi with a measured half power steering angle of 155° while maintaining a side lobe level (SLL) less than -10 dB. Further, the second ECAA showed a measured peak gain of 12.8 dBi with a measured half power steering angle of 144° while keeping the SLL less than -10 dB. These scan angles of the first and second types were extended about 66.7% and 54.8%, respectively from the conventional patch array with the same size. Lastly, two types of 8 × 8 array modules for 2-D beam steering were verified at 5.8 GHz and the first type showed a maximum peak gain of 21.0 dBi. Further, the 2-D half power steering angles in E- and H-planes of the second type were about 145° and 137°, respectively.

This article presents the design and fabrication of a micromachined 300 GHz planar array slotted waveguide antenna utilising the silver-coated SU-8 photoresist layer technology. The array is configured to be built from five SU-8 layers of equal thicknesses. The top layer is devoted to form the 8×8 slots. The following three layers are to form the feed and radiating waveguides. The bottom layer is to enclose the design and allocate the input port. An H-plane waveguide bend based on the matching steps is designed and integrated with the proposed array. This is to maintain a precise alignment with the standard waveguide flange WR-03 and facilitate the measurement. Also, two brass plates are used to clamp the five layers together and tight them via screws in order to minimise the losses. The simulated antenna realised gain is 24.59 dBi, and the 3-dB gain bandwidth is 4.5 GHz. The radiation patterns are very directive, having low side lobe levels. The reflection coefficient has been measured and presented. The proposed micromachined antenna array is directional and low-profile and may find applications in indoor wireless applications and sensors.

The design and algorithm research of the digital holographic imaging system in the near infrared band is carried out in this paper, which is based on the infrared band laser and the planar array detector. We built a set of a near infrared coaxial digital holographic imaging system based on the 1550 nm wavelength distributed feedback laser, and the system was calibrated with the resolution plate. At the same time, the compressed sensing algorithm is used to reconstruct the holograms of the resolution plate and other objects, which effectively inhibits the influence of noise. It proves that infrared digital holographic imaging technology is a new potential phase-contrast imaging method.

In this paper, a low-profile broadband dual-polarized planar phased array with a wide scanning range is presented at 12 GHz — 26 GHz. The antenna element is made up of superstrings, patches and metal columns, and the total thickness is 4.094 mm. The dielectric layer and metal columns not only promote the scanning angle, but also provide a solution to improve the matching response. The VSWR is lower than 2.15 and 3.61, severally, with scanning to 50° and 60°. At the same time, the simulation results of a $4\times 4$ planar array show that active VSWR is lower than 1.78 at $\theta=0^{\circ}$ and $\varphi=0^{\circ}$ in the entire design frequency band.

Multi-beamforming antenna is increasingly needed for many applications. In this paper it is investigated multi-beamforming antenna by using Rotman lens and array antenna with some modified configurations. They are in plane, folded, and folded with modified planar array configuration. Those configurations successfully make five beam directions in -20, -10, 0, 10, 20 degrees with maximum deviation of 2 degrees. The folded with modified planar array configuration shows the best performance for both average sidelobe level (SLL) and average gain.

Monopulse radars operate with simultaneous beams and are used for tracking purposes, relying only on hardware to provide a real-time indication of the target position. A monopulse array and its feeding network is implemented and tested, in the frequency of 5.4 GHz, based on patch antennas using dieletric to provide wide bandwidth and high gain. The system field styrofoam as pattern was evaluated in two different environments, a shielded room and an indoor area. Results agreed with simulation for either individual elements as well as the final integrated monopulse array.

The high-precision target echo generation in the field of radar systems is particularly important for large-scale, comprehensive testing of radars. Conventional echo generation techniques often use planar array air feed to simulate echoes. However, it is complicated and expensive to achieve the echo generation with traditional planar array. Therefore, this study proposes a high-precision target generation technique based on one-dimensional linear arrays. The simulation system achieves the target radial high-precision simulation through DRFM technology; the target azimuth high-precision simulation is achieved through differential GPS technology; and the target elevation high-precision simulation is realised through vertical one-dimensional linear array antenna switching. The semi-physical simulation system presented here has the advantages of simple control, low cost, low link loss, easy maintenance, and high simulation target accuracy. Finally, the system was tested in the field to verify the theoretical concept of the article.

A multi-port element approach, engineered to address practical design challenges of very high-frequency (VHF) phased array radar systems, is presented in this communication. A cornerstone of the antenna element design is its simplicity, which counteracts the mobility issues of physically large and unavoidably bulky ground-based VHF radar systems. The multi-port element introduces a third dimension in the otherwise planar array configuration. Using a nonlinear optimization scheme to realize a set of matching networks for the element, the active loading from surrounding elements in the array environment is suppressed resulting in a nondistorted embedded element pattern. The element is compared to the resembling Yagi–Uda design in terms of standard multi-port and radar metrics. The simulated results indicate that the element enables a significant suppression of grating lobes when beam steering within a limited angular sector, which in turn has an overall positive impact on the array performance.

A novel feeding method for a dielectric resonator array antenna is introduced. Unlike in a corporate feed network, power dividers or quarter-wave transformers are not needed in the new feeding scheme as the design is based on the standing-wave concept. Consequently, the feed network is greatly simplified, and undesired spurious radiation in the feeding network is minimized. The simulated and measured results are in good agreement. A 3-D printer is utilized where the entire array structure is fabricated as a single piece with a dielectric material of polylactic acid. The 3-D printer provides a cost-efficient, simple, and rapid manufacturing process. This work was supported by Comunidad de Madrid under Projects S2018/NMT-4333 MARTINLARA-CM and TEC2016-80386-P. Publicado

This paper describes an innovative architecture of dual-band planar array for short-range tracking radar applications. The proposed antenna consists of two integrated patch arrays and it works in the L-band and Ka-band. The structure is characterized by compact size and lightweight, thanks to the concept of sharing the same PCB and mechanical chassis for dual-band operation. One of the key aspects, besides the interoperability of the two patch arrays, is the use of dielectric rods that increase the realized gain while minimizing the required number of elements. As a consequence, the beamforming network is simplified, and the reliability of the module is significantly improved. The proposed dual-band array provides a gain higher than 28 dBi with low sidelobes and controlled narrow pencil beam, making it ideal for highly accurate radar tracking.

This paper presents the design of 2-D phased array of antennas to radiate collinear multiple beams properly distributed for near-field (NF) focus (NFF) applications. In the design, the 2-D array is first decomposed into single-column subarrays, where each of the subarrays is identically excited to radiate a vertically NFF beam with the focal points located at a designated distance along the boresight direction of each subarray aperture. Afterward, the NFF column subarrays become the elements of a 1-D horizontal collinearly located array to radiate horizontally NFF multiple beams. The horizontal NFF beamforming network is implemented by extending the basic concept of conventional Rotman lens beamformer for directional NFF multibeam applications. Thus, three feeding points are selected to determine the lens’s profile such that the produced phases via the modified Rotman lens can be used to feed a planar array to radiate three NFF beams when the lens is excited at the three selected points, respectively. This antenna set is realized at 2.45 GHz for radio frequency identification applications to demonstrate the implementation concept. Both the simulation and experimental measurement results are shown to validate the feasibility.

In this paper, a high-gain double-sided printed dipole array antenna is designed for Ad-Hoc network nodes. By changing the shape of the oscillator element, it is designed as a novel exponential gradient sector structure to achieve good broadband characteristics. The antenna dipole radiator arm is symmetrically distributed on the upper and lower surfaces of the dielectric substrate. Taking the radiator element as the array element, an 8-element planar array with a reflecting plate is designed. Simulations show that the proposed printed dipole array antenna has a bandwidth of 400MHz for voltage standing wave ratio (VSWR) < 2, which can meet the frequency band required by the Ad-Hoc network nodes. The experimental verification of the antenna shows that the working bandwidth is 480MHz, the relative bandwidth reaches 14.5%, and the experimental result is in good agreement with the simulation result. The maximum gain of the antenna at the frequency points of 3.3 GHz, 3.5 GHz, and 3.7 GHz are all around 20.5dBi.

LCD projectors are widely used to support presentations on teaching and learning activities, meetings, seminars and so on. This study discusses the design and manufacture of a 2x2 planar array triangular patch microstrip antenna as a receiving antenna for wireless LCD projectors to overcome cable length limitations. The research method starts from the design, simulation of design results, fabrication, parameter measurement and antenna testing. The design was carried out using the CST Studio Suite application, then made on the FR-4 PCB. Testing includes measurement of antenna parameters and performance. In testing the antenna parameters, the values ​​obtained are in accordance with predetermined specifications, gain above 3 dB, VSWR below 2 dB, return loss below -10 dB and unidirectional radiation pattern. The antenna performance test results show that the quality of signal and video reception from the microstrip receiving antenna that has been made is still better than the default antenna for the receiver device. Keywords: Microstrip triangular patch plannar 2x2 elements, wireless LCD projector

© 2021 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works, In this paper, a planar active phased array antenna demonstration with linear polarization (LP) at Ka Band (28-30 GHz) is presented. The proof of concept is carried out to evaluate the possible problems that may arise, to analyze possible calibration stages and to assess the viability of the integration of an active system with a Multi-Channel Beamforming Module (MCBM). To fulfill this task an 8times 8-element planar array arranged in column subarrays of 1times 8 elements for 1D beam steering is proposed. The single element consists of a printed circular patch connected to a microstrip feeding line through metallic vias in a multilayered structure. Both the amplitude and phase distributions are performed by a commercial integrated circuit (IC) designed for transmission purposes, from the common port to each of the 8 output ports. Thus, an evaluation of the IC performance is also included within this work. Despite the inherent amplitude and phase feeding errors of the IC, the beam-steering accuracy of the system is reasonable. A nice correspondence between the simulated and measured 8times 8-element array beam steering directions is obtained, with errors below 1° in the steering of the beam, This work was supported in part by the Spanish Government, Ministry of Economy, National Program of Research, Development and Innovation through the Project FUTURE RADIO ’’Radio systems and technologies for high capacity terrestrial and satellite communications in an hyperconnected world’’ under Grant TEC2017-85529-C3-1-R, and in part by the Project JETSTREAM ’’Desarrollo de una antena banda KA embarcada para la prestación de servicios de acceso a Internet por satélite en aviación comercial’’ in collaboration with TELNET Redes Inteligentes S.A. under Grant RTC-2015-3495-7

Unmanned aerial vehicle (UAV) technology has been applied in many fields with the rapid development in recent years. Although it helps to improve the working efficiency and convenience of life, some problems exist in public security caused by the high difficulty of UAV detection due to its small size. Thus, the technology of UAV detection attracts more and more attention to researchers. Electromagnetic wave detection of UAV with radar is an effective and attractive technique because of the long detection range and the all-weather capacity. A cylindrical phased array radar system for effective UAV detection is introduced in this paper. The system has a better ability of omnidirectional scanning compared with planar array radars, and it can also flexibly change the beam direction and illumination time to the target by using the phased array, which brings great benefits for UAV detection under strong clutter environment. The system’s hardware structure, working principle and signal processing flow designed for strong clutter suppression are specified in the investigation. Experimental results show great potential of this system in UAV detection.

This paper presents a 5G millimeter wave (mmwave) low-profile 2 × 2 planar tightly coupled dipole subarray (TCDS) covering the bandwidth of 24.25 – 40 GHz which is the frequency range 2 (FR2) designated by 3rd Generation Partnership Project (3GPP). The element antenna of 2 × 2 array is a subarray consisting of 4 × 4 Tightly Coupled Dipole Array (TCDA) unit elements. Total thickness of the proposed antenna is 0.9 mm (0.07 λ low at 24.25 GHz), and the maximum realized gain is 8.3 dBi at the frequency and 12.4 dBi at 40 GHz. This realized gains satisfy the specification of the peak effective isotropic radiated power (EIRP) at 24.25 GHz, 30 GHz, 37 GHz and 40 GHz which are 23.3 dBm, 24.3 dBm, 26.6 dBm and 27.4 dBm, respectively, with transmitter power of 8.1 dBm per a channel. In addition, the cumulative distribution function (CDF) of the EIRP to evaluate the spherical coverage is presented.

A circular planar array composed of four equilateral triangle patch antennas with a common triangular ground plane is proposed. The array is a building block for a geodesic dome phased array antenna (GDPAA) based on an icosahedron structure, primarily intended for use in the UHF amateur satellite band of 435-438 MHz. Due to the relatively long wavelength of this band, a novel design for a low-cost GDPAA with a reduced footprint is proposed. It is found that if individual elements are placed in a circular lattice, the footprint is reduced and the overall array performance and antenna isolation are improved.

In this chapter, a highly directive small-gap photoconductive dipole array antenna is presented for imaging system operating at terahertz frequencies. The array antenna is formed on a single photoconductive substrate to make it compact and suitable for terahertz imaging applications. The presented photoconductive dipole array antenna improves the gain as well as directivity; therefore, it is useful to enhance the imaging capabilities to address the considerations such as limited depth-of-field (DoF), that is, the distance over which an object is considered in focus, and size, weight, and power (SWaP) of terahertz source for imaging applications. These are important considerations for applications such as standoff imaging and surveillance of moving targets where the high angular resolution as well as extended DoF is the key for successful detection of hidden explosives and illicit drugs. In addition to this, a technique of using frequency selective surface with photoconductive array antenna is also presented to further enhance the directivity of the radiating structure to yield high image resolution. Moreover, by using this technique, the radiation energy has been confined to the desired frequency band rather than spreading over a wide spectrum range.

This paper evaluate the parametric effects due to mutual coupling between inter-elements using balance antipodal Vivaldi antenna (BAVA) with high permittivity dielectric director in an array configuration. An elliptical shaped dielectric-director made by the substrate of Rogers RO-3010 with high permittivity of e r =10.2 is used with BAVA in order to enhance the radiation characteristics of the antenna in focus. An antenna (66mm × 60.75mm) in dimension designed on FR4 substrate, which covers ultra-wide frequency band of 114.28% from 3GHz to 8GHz. The performance of an antenna with dielectric director is evaluated in a capacity of gain enhancement, directivity, regular radiation pattern with low side lobe level and beam width. Further, the use of dielectric directors in planner antenna array based configuration can provide significantly change in radiation characteristic and also provide help in the reduction of mutual coupling inter-elements. The same results can be obtained by using four elements with high permittivity dielectric directors in the planner antenna array based arrangement instead of eight or more elements without directors. This is an alternative way to reduce the number of elements in an antenna array based system. The design and optimization progression is realized out using CST simulation software.

The ever-increasing number of RF-based advanced driver assistance systems (ADAS) applications onboard an autonomous vehicle presents with an opportunity for co-locating and sharing the RF front-ends, which in this context refers to the antenna and its associated circuitry of a RADAR. This paper proposes two sparse planar antenna array topologies synthesised for 77 GHz, by replicating a novel subarray, designed using eight isotropic antenna elements. Elements were placed manually to synthesise the novel subarray geometry, while the superarray topologies were constructed by placing subarrays of a particular orientation in a uniform superarray or by placing subarrays with fixed or optimally selected orientations in a sparse planar array, modified genetic algorithm (MGA) was employed to determine only the optimal subarray positions in the first case while the latter used it to choose both position and orientation, subject to the critical constraints dependent on the selected ADAS applications. Ultimately the comparative study of the topologies showing better performance of proposed topologies are discussed.

In wind tunnel experiments, it is significant to accurately measure the parameters of the model attitude after loading. Linear array CCD high-speed, high-resolution features with a cylindrical lens and planar array CCD array as an auxiliary to be measured together complete the wind tunnel attribute measurement experiment of high-speed test substances with high precision. The special low distortion lens are designed and fabricated using linear array CCD cylindrical lens, lens distortion design specifications are better than 0.05%, in actual test, lens distortion in the middle of the view field is smaller than 0.1%, the edge position distortion is relatively large, but is not more than 0.3%, and is less overall distortion. It is satisfied to the requirements of the large field of view, and high-precision in wind tunnel experiments.

This paper focuses on characterization testing and validation of the dynamic model of a new type of high-damping density electromagnetic-based damping device (EMD) referred to as Magneto-Solid Damper (MSD) in which an eddy current damping mechanism acts in parallel with a solid friction mechanism to dissipate the input kinetic energy. The proposed MSD consists of a ferromagnetic plate, two copper plates placed on two sides of the ferromagnetic plate in parallel, and a planar array of permanent magnets (PMs) placed between the ferromagnetic plate and each of the two copper plates. The PMs arrays are attached to the ferromagnetic plate through non-magnetic friction pads. The friction force is developed between these friction pads and the ferromagnetic plate when the PMs arrays move relative to the ferromagnetic plate. The motion of the PMs arrays relative to the copper plates, on the other hand, generates the eddy current damping. A laboratory prototype of the proposed MSD has been designed and fabricated for the purpose of characterization testing. Finite element and simplified analytical models of this damper have also been developed to analyze the magnetic interaction between the PMs arrays and the ferromagnetic and copper plates. A dynamic model has been developed to characterize the force–displacement behavior of the proposed MSD. The parameters of this dynamic model are identified through a series of characterization tests on the prototype MSD under harmonic excitations of different frequencies. The identified dynamic model is validated by subjecting the prototype MSD to real ground motion records. It is concluded that that the proposed dynamic model is capable of describing the force–displacement behavior of the proposed MSD for a wide range of operating conditions.

A dual-polarized antenna array for 4G base stations is presented in this paper. The antenna array is a 2×4 uniform planar array and is composed of printed dual-polarized dipole antennas, operating in 1.7-2.2 GHz. By loading the metal plate and using antenna decoupling surface, the mutual coupling of the array is below -20dB.

Using the statistical theory of optimization of radio engineering systems the optimal method for the formation of coherent radar images of surfaces in airborne synthetic aperture radar with planar antenna arrays is obtained. This method summarizes several modern modes of terrain observation and is fully consistent with current trends in the creation of cognitive radars with the possibility of restructuring the beam pattern in space and adaptive reception of reflected signals. Possible modifications of the obtained optimal method for the operation of high-precision airborne radars with a wide swath are presented. The analysis of the limiting errors of measurement of the desired parameters is carried out and analytical expressions are obtained for the nonstationary ambiguity function of the resulting structure of an airborne radar with a planar antenna array.

The optimization problem of statistical synthesis of the method for radar cross section (RCS) estimation in a radar scatterometer with planar antenna array is solved. The desired RCS is given as a statistical characteristic of a spatially inhomogeneous complex scattering coefficient of the studying media. The maximum likelihood method was chosen as the optimization method. The obtained results make it possible to determine the multichannel structure, the optimal method of surface observation and the potential space resolution in aerospace scatterometric radars. The presence in a signal processing algorithms of the optimal decorrelation operation of the received spatio-temporal signals makes it possible to form superresolution radar images of surfaces.

Sonar, radar and communication systems solely depend on antenna arrays for signal attainment. These arrays are capable of producing directional signals which can be steered in a certain direction. Faulty elements in an array will result in distorted radiation pattern with increased sidelobe levels. Far-field faulty antenna detection is necessary due to the near field repairing at complex systems like spacecraft. This paper proposes simulated annealing (SA) optimizing method to find the faulty element’s location in a linear array. In this study, a Chebyshev array is presented with the SA optimization method to detect faulty element location with a random permutation of failure locations tested. This method can successfully detect faulty antenna in a linear array. Even though, this method is developed for linear array it can easily be adapted to a planar array.

Antenna miniaturization is a necessary technique to decrease an antenna size for providing a compact transceiver system. The optical approach technique adoption in the Terahertz (THz) spectrum, such as using a lens, requires a very small wavelength compared with the optical component dimension to avoid large diffraction effects and fulfill the geometrical optics approach. The impact is a large device dimension obtained after combining an antenna with an optical lens. This paper investigates radiation performances of a size reduced THz lens antenna fed with a planar crossed bowtie antenna affected by applying optimum matching layers. Simulation results by using CST Microwave Studio show that decreasing gain, radiation efficiency, and beamwidth occurs significantly when the reduction is coming to the main beam radiation. The matching also has a contribution to improve those parameters due to its characteristic to reduce wave reflections on the boundary surface. The lens size reduction offers an advantage of more suppression on side lobes. These results can be considerations to design a planar array configuration of THz waves sensors based on the quasi-optical antennas.

In this paper, a new configuration of four elements circular equivalent planar array has been proposed to achieve high gain and directivity with lower sidelobe level. After being designed and simulated, the proposed antenna array has achieved high directivity of 15.3 dBi with 85 % radiation efficiency. Besides, the array has a maximum realized gain of 14.51 dB and low sidelobe level of − 16 dB. The proposed antenna array has been evaluated by comparing its performances with four elements of MIMO and planar antenna arrays. It is observed that the proposed array shows greater performances in terms of all parameters compared to the other two arrays. Also, the proposed array has maximum isolation of below − 35 dB between two nearby elements. In turn, the high directivity of the proposed antenna array resonating at 5.8 GHz with very minimum return loss which makes it suitable for Radar application. Contribution-High gain and directivity have been achieved by proposing a new Circular Equivalent Planar Array with lower sidelobe level and minimum mutual coupling effect.

By changing the excitation phase of each antenna element, the influence of the excitation phase on planar antenna array of magneto-electric dipole antenna is studied. The 2×3 planar antenna array is composed of six magneto-electric dipole antennas. The distance between each antenna element is 1.25 mm. With different excitation phases of antenna elements, the planar antenna array has different gain and radiation pattern while the reflection coefficient is identical. When the array elements are excited by the same phase at the same time, the planar antenna array achieves a wide operating bandwidth of 53.7% covering 45.0 GHz to 78.0 GHz. And it achieves a high gain of 17.8 dBi in the direction of maximum radiation. The proposed planar antenna array can be well used in millimeter wave band.

With the advent of Active Electronically Scanned Array (AESA) technology in the design and development of advanced multi-target handling Radar and Electronic Warfare (EW) systems, a new EW system with a Phased Array of a uniform spacing was developed, whose beam can be controlled using adaptive software programs. The critical EW system is recognized with miniaturized Planar Arrays using Transmit/Receive modules or T-R modules. The T-R modules use a novel core technology for the development of AESA technology. The planar arrays are miniaturized using multifunctional Monolithic Microwave Integrated Circuits (MMIC) with an inbuilt digital circuitry for beam steering, which requires high quality and different levels of programming using Field Programmable Gate Arrays (FPGA's). The AESA generally consists of thousands of T-R modules which can individually spread their signal emissions out across a band of the frequencies and sensitively receive the echoes from target objects, allowing it to broadcast transmitting signals while remaining stealthy and greatly increasing the detection and tracking abilities. Implementation of beam steering and control algorithms has to be designed in the frequency of 5–18 GHz for T-R module based planar arrays.

In beamforming, the signals from the particular direction are weighted, whereas signals from other directions are attenuated. In uniform linear array (ULA) of phased array antennas, the beamformer combines the signals linearly from each element of the array and achieves directionality. In uniform planar array (UPA) the antenna elements are arranged in a plane. These antennas can be steered electronically by adjusting the phase and gain. This paper deals with types of beamforming such as conventional, tapered, optimum and adaptive beamforming. In adaptive beamforming, the Sample Matrix Inversion (SMI) method is discussed along with the concept of diagonal loading. The use of diagonal loading reduces the sidelobe level by 12 dB and 25dB in linear and planar array respectively for 100 input training samples.

This paper presents an evaluation procedure of a commercial integrated circuit (IC) for phased array antenna beam steering purposes within mobile satellite communication applications at Ka Band (28-30 GHz). It allows to control amplitude and phase delivery from one common port to 8 independent channels. Therefore, only the transmission system is evaluated. Two different passive arrays are proposed to evaluate IC performance: a 2x2 planar array with switchable circular polarization (SCP) capabilities and an 8x8 planar array fed by columns for azimuth beam steering with linear polarization (LP). Thus, since the first array is not as big enough for evaluating beam steering performance, it is only used for SCP performance evaluation. A second array, which is bigger but not circularly polarized, allow beam steering evaluation. Measurements of the proposed full integrated systems will be presented at the conference.

This paper introduces a 2D angle-of-arrival (AoA) estimator, which has a 6–18 GHz 7-element nonuniformly spaced array (NSA) and a Direct Data Domain- (D3-) based AoA algorithm for a 2D isotropic-element planar array (IEPA). A 2D calibration and data-transformation method is developed to convert the NSA data to the output of the IEPA, so that the NSA-measured data can be used in the D3 algorithm. Using the steering vector (SV) of the IEPA and the results derived from the D3 method, a new 2D AoA searching method is also developed, which offers frequency-independent performance defined by the probability of AoA estimation, when the required estimation accuracy and signal-to-noise ratio (SNR) are given. For the applications of electronic support measures, this paper also presents the use of precalculated SV and data-transformation matrix databases built on preselected frequency points and a 2D-angle grid that is close to uniformly distributed directions. The simulation results show that with good SNR (≥15 dB), the estimator can have 50% probability of AoA estimation with root mean square error (RMSE) less than or equal to 1° using just a few samples from the NSA. Moreover, the study focuses on the applications with low SNR by using more samples from the NSA. Results show that the estimator has 52% and 80% probabilities of AoA estimation with RMSE ≤1° and 5°, respectively, for phase- or frequency-modulated radar pulses, when the SNR is within [−10, 0] dB. The study also shows that the estimator prefers a circular-shaped planar array with a triangular interelement pattern, since it presents more symmetrical characteristics from different azimuth angles.

Over-the-air (OTA) measurement techniques are essential to verify the performance of antennas and wireless devices. The random line-of-sight (random-LOS) measurement setup offers the advantage to test the OTA performance of antennas mounted on cars in existing, or new, semianechoic chamber and full-anechoic chamber. Hence, reusing currently available infrastructures together with a cost-efficient measurement setup will reduce OTA costs for the automotive industry. In random-LOS, a plane wave is synthesized in the test zone, where the far field of a radio base station is emulated. We present measurements and simulations of a random-LOS OTA setup operating at the 2.7 GHz band. We compare the cases when the emulated base station signals are generated by a single dual-polarized bowtie antenna, a uniform linear array of bowties and a uniform planar array of bowties. The evaluation of the standard deviation of the reference received signal in the test zone shows good agreement between measurements and simulations. We show with measurements that for a test zone with a radius of 0.5 m, the standard deviation can be less than 0.8 dB for the analyzed random-LOS OTA setup.

Active metasurfaces with novel visible and infrared (vis/IR) functionalities represent an exciting, growing area of research. Rectification of vis/IR frequencies would produce needed direct current (DC) with no inherent frequency limitation (e.g. no semiconducting bandgap). However, controlling the materials and functionality of (nano)rectennas for rectifying 100 s of THz to the visible regime is a daunting challenge, because of the small features and simultaneously the need to scale up to large sizes in a scalable platform. An active metasurface of a planar array of nanoscale antennas on top of rectifying vertical diodes is a 'nanorectenna array' or 'microrectenna array' that rectifies very high frequencies in the infrared, or even higher frequencies up to the visible regime. We employ a novel strategy for forming optical nanorectenna arrays using scalable patterning of Au nanowires, demonstrate strong evidence for spectral-selective high-frequency rectification, characteristic of optical antennas. We discover a previously unreported out-of-equilibrium electron energy distribution, i.e. hot electrons arising from plasmonic resonance absorption in an optical antenna characterized by an effective temperature, and how this effect can significantly impact the observed rectification.

Conformal arrays have great potential for providing high performance including wide angle coverage, volume saving and aerodynamic superiority. These potential benefits are attractive for the aircraft that has limited area available for radar installation and requires high radar performance. Conformal conical array is always chosen for its similarity to the aircraft nosecone. The goal of the study is to evaluate the airborne conformal conical array radar performance including anisotropy, beampattern, 3-d cover, power-aperture (PA) product. Numerical results show that the conical array has wider angle coverage and superior performance on PA product than the conventional planar array.