Low Sidelobe Level Research Articles

Radar Pulse Compression with Optimized Weighting Window for SAR Receivers

This paper proposes a novel design of a software-defined matched filter (MF) for digital receivers of synthetic aperture radar (SAR). The block diagram of the proposed receiver is described in detail. The purpose of this filter is to produce a SAR pulse with higher compression ratio (CR) and lower side lobe level (SLL) than that produced by the conventional MF. The proposed design is based on the idea of time windowing of the SAR pulse to construct the transfer function of the receiver filter. The shape of the proposed time-domain window is optimized to achieve the filter design goals including the minimization of the SLL and the realization of the target value of the CR. The transmitted SAR pulse is, first, subjected to linear frequency modulation and then subjected to the optimized window. The width (time duration) of the proposed window is divided into equal time intervals. The proposed time-domain window is constructed as a sequential continuous piecewise linear segments. The instantaneous value of the time-domain window at the start of each time interval is optimized so as to achieve the optimization goals. The width of the time-domain window is shown to be proportional to the width of the compressed pulse after optimization. The number of the time intervals into which the time duration of the window is divided is shown to have a significant effect on the optimization results. The particle swarm optimization (PSO) technique is then applied to get the window shape that minimizes the SLL for a specific predetermined value of the pulse CR. It is shown that the iterations of the PSO are fastly convergent and that the applied algorithm is computationally efficient. Also, it is shown that the desired value of the pulse CR is achieved with accuracy of 100%. Moreover, the achieved SLLs are about − 65,mathrm{dB}, - 90,mathrm{dB}, - 114,mathrm{dB}, and - 133,mathrm{dB} for pulse CR of 5, 3, 2, and 1.5, respectively. Finally, for practical implementation of the introduced SAR pulse processing technique, the proposed optimized window is placed as a building block in a software-defined receiver of the SAR system.

W‐Band High‐Efficiency Waveguide Slot Array Antenna with Low Sidelobe Levels Based on Silicon Micromachining Technology

A high-efficiency waveguide slot array antenna with low sidelobe level (SLL) is investigated for W-band applications. The silicon micromachining technology is utilized to realize multilayer antenna architecture by three key steps of selective etching, gold plating and Au-Au bonding. The radiating slot based on this technique becomes thick with a minimum thickness of 0.2 mm and accompanies with the decrease of slot's radiation ability. To overcome this weakness, a stepped radiation cavity is loaded on the slot. The characteristic of cavity-loaded slot is investigated to synthesize the low-SLL array antenna. The unequal hybrid corporate feeding network is constructed to achieve sidelobe suppression in the E-plane. A pair of 16 × 8 low-SLL and high-effciency slot arrays is fashioned and confirmed experimentally. The bandwidth with the radiation effciency higher than 80% is 92.3–96.3 GHz. The SLLs in both E- and H-planes are below −19 dB.

A broadband Fabry–Perot resonator antenna using partially reflecting surface with positive reflection phase gradient

A novel Fabry–Perot resonator antenna with a wide impedance- and gain-bandwidth is proposed in this paper. A wideband aperture-coupled microstrip antenna is used as the primary source, and a single-layer frequency selective surface with a positive reflection phase gradient is designed as a partially reflective surface. To validate the proposed approach, a prototype antenna operating in the X-band is designed, fabricated, and measured. Both simulation and measured results indicate that the proposed antenna exhibits wideband characteristics. The measured impedance bandwidth (|S11| < −10 dB) is 64.4%, ranging from 8.68 to 15.12 GHz. The experiments demonstrate that a 3 dB gain bandwidth of 31.9% from 8.61 to 11.80 GHz with a peak gain of 14.0 dBi at 10 GHz is achieved. In addition, the proposed antenna reveals good directional radiation patterns, low side-lobe level, and low cross-polarization over the whole working band.

Low-Scattering-Cross Section Thinned Phased Array Antenna Based on Active Cancellation Technique

In this article, a novel approach to simultaneously reduce the scattering cross section (SCS) and lower sidelobe level (SLL) as well as the cost of a phased array is proposed, which is a combination of active cancellation and array thinning techniques. Two 10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times\,\,10$ </tex-math></inline-formula> planar microstrip phased arrays are designed to validate the proposed concept, including a full array and a thinned array with 20 passive elements. In the thinned array, the passive elements are made use of and terminated at an optimized position with short-circuited loads to generate scattering fields with the required magnitude and phase for cancellation of the scattering fields from the active elements. Furthermore, the positions of the passive elements are optimized by a multiple dimensional discrete particle swarm optimization (MDDPSO) algorithm to achieve a low SLL. It is theoretically predicted that the thinned array features a low SLL below −18 dB in a scan range of ±45°, and SCS reductions of 21 and 9.1 dB in 7.3–10.1 GHz compared to an equal-sized metallic plate and a full array, respectively, which are further verified in simulations and measurements. It is also remarkable that the array cost is reduced due to array thinning, at the cost of an approximately 1 dB gain drop.

Optimum Extrapolation Techniques for Two-Dimensional Antenna Array Tapered Beamforming

Optimizing antenna arrays is essential for achieving efficient beamforming with very low sidelobe level (SLL) where adopting tapered window functions is one of the straightforward efficient techniques for achieving this goal. Recently, two-dimensional (2D) beamforming has been extensively required for many applications; therefore, this paper proposes two extrapolation techniques applied to one-dimensional (1D) tapered functions to efficiently feed 2D antenna arrays using cross-linear and adaptive radial tapering techniques. The first proposed 2D cross-linear tapering technique determines the 2D tapering coefficients by Hadamard multiplication of two right-angled grids of repeated 1D functions, while the second proposed adaptive radial tapering technique locates the antenna element in the 2D array in terms of its radial distance with respect to the array center, then converts this distance to an element index in a virtual 1D tapering window to determine the element weighting value. The adaptive radial tapering technique is optimized for achieving the minimum SLLs. The two proposed techniques are analyzed and discussed, where it is found that the adaptive radial tapering provides deeper SLLs compared to the cross-linear tapering technique. The two extrapolation techniques are examined for four window functions including triangular (Bartlett), Hamming, cosine-square, and Blackman windows, and the simulation results show that for extrapolating the Blackman window using adaptive radial tapering, a –50 dB SLL can be achieved which is independent on the array size, while cross-linear tapering provides –35 dB and –41 dB SLLs for and antenna arrays, respectively.

Design and Simulation of Wideband, High Gain Matrix Antenna with Beam Steering and Low Side-Lobe Levels Features

In this paper, a matrix antenna composed of radiating pixels elaborated in meta-materials is presented. The pixels are surmounted with a frequency selective structure and closed with four metallic walls. The cavity is excited by a radiating patch and filled with dielectric. This dielectric makes it possible to reduce the overall width of the pixel by increasing the dielectric length of the cavity while maintaining the performances of the pixel. The pixel is reduced to a width of 50.96 mm (0.34*λ) at 2 GHz. The -10 dB fractional bandwidth of the pixel is 22% (2-2.5 GHz). The pixel is then placed in a 17 elements matrix to achieve high steering angles. The optimization focuses on the steering capacity, the bandwidth and the side-lobes levels. On the whole band, the steering angle is more than 70° and the antenna achieves low side-lobes levels at less than -9.9 dB. A device to reduce the mutual coupling between the elements by using soft surfaces is also presented. These surfaces allow to widen the matching band while the steering is produced.

Amplitude and Phase Independently Adjustable Transmitarray Aperture and Its Applications to High Gain and Low Sidelobe Antenna

This article introduces an amplitude and phase independently adjustable transmitarray aperture with a thin profile and low cost to fabrication characteristics, and a transmitarray antenna (TA) featuring the high gain and low sidelobe level (SLL) is realized based on it. The TA is made up of a standard feed horn and a transmitarray aperture, each of which comprises a three-layer metasurface that is well-designed to tune the transmitted phase and amplitude on its own. As a result, the transmitarray aperture can cover the 360° phase range required for phase compensation while also realizing the amplitude distribution calculated by the Taylor design, contributing to the low SLLs. The advantage of independently controlling the amplitude and phase not only enables the proposed TA to be easy to realize and less cost on optimization but also improves the performance of high gain and low SLLs with a low profile and easy fabrication. Theoretical analyses and simulations are carried out, and a prototype is fabricated and measured. At 10 GHz, the measured peak gain is 21.16 dBi, with SLLs of −31.21 and −29.93 dB in the H- and E-planes, respectively. As a result, the tight agreements between measurement and simulation validate the design concept.

ШИРОКОПОЛОСНОЕ ДОУ НА ОСНОВЕ ПЕЧАТНОЙ ЛИНЗЫ РОТМАНА ДЛЯ МНОГОЛУЧЕВЫХ АНТЕННЫХ РЕШЕТОК

The most well-known beamforming device (DOU) (for linear and flat MAR) is the Rothmanlens, which is of great interest because it allows you to form a fan of MAR rays in a wide spatialsector of angles (wide-angle scanning), has a fairly high efficiency and MAR with a lens Rothmanhas a low level of side lobes. Another advantage of the MAR with a Rothman lens is the weak dependenceof the position of the rays in space on frequency, in contrast to the MAR with a Butlermatrix DOE, in which, at a high efficiency (theoretically 100%), the position of the rays dependson the frequency. However, the previously developed analogs of the Rothman lens are large andrequire additional components in the design, which affects the transmission coefficient of the lensin the operating frequency range from 2 GHz to 20 GHz and the consistency of the device withother components of the transceiver equipment. It follows that the study and modernization of lensstructures in relation to multibeam antenna arrays (MAR) is a topical topic for research. The purposeof the work is to propose a method for calculating the Rotman lens, modernize the lens design,make a lens model and conduct an experimental study of the lens in order to obtain constructivemethods for optimizing the characteristics of the Rotman lenses for use in MAP in the frequencyrange from 2 GHz to 20 GHz. In the results of the article, the dimensions of the lens, themass of the lens, the transmission coefficient, and the simplicity of the design are estimated incomparison with the previously developed analogues. A technique for calculating the geometry ofa Rotman lens is proposed, the SWR of a printed Rotman lens is experimentally studied on a vectornetwork analyzer, constructive methods are obtained for optimizing the characteristics of Rotmanlenses for use in multibeam antenna arrays. A model of a broadband Rotman lens in microstripdesign with a maximum SWR of 1.3 (S21) in the operating frequency range from 2 to 20 GHz wasmade, the lens size was 150x100, and the lens weight was 0.4 kg. According to these parameters,the Rothman lens surpasses the analogues developed earlier.

A Back-Fire to Forward Wide-Angle Beam Steering Leaky-Wave Antenna Based on SSPPs

We demonstrate an efficient back-fire to forward wide-angle beam steering leaky-wave antenna (LWA) based on a large dispersion gradient planar spoof surface plasmon polariton (SSPP) transmission line (TL) with split-ring units. To convert the highly confined SSPP waveguiding mode to a radiation mode, two arrays of metallic patches are periodically arranged on both sides of the SSPP TL. The patches are designed as two combined half-elliptical shapes to mitigate the open stopband effect and enhance the radiation performance. We propose a theoretical method to interpret the mechanism and predict the directional pattern of the LWA. To verify the proposed method, the SSPP TL and LWA prototypes are fabricated and measured. The calculation, simulation, and experimental results match well and show that the main beam of the LWA can steer a wide range of 112&#x00B0; from back-fire (&#x2212;90&#x00B0;) to the forward quadrant of 22&#x00B0; passing through the broadside in 6.3&#x2013;11 GHz, demonstrating a large scanning rate of 2.07&#x00B0;/&#x0025;. Furthermore, the LWA also possesses the advantages of low profile, high average gain (12 dBi), high average efficiency (95&#x0025;), and low sidelobe level (&#x003C;&#x2212;13 dB). This work provides an alternative route to achieving wide-angle LWAs for promising microwave radar and wireless communication applications.

Синтез разреженной линейной антенной решетки с сохранением ширины главного лепестка и минимальным пиковым уровнем боковых лепестков при помощи генетического алгоритма

This paper proposes a genetic algorithm as an instrument for antenna array thinning. The algorithm with a deliberately chosen fitness function allows synthesizing thinned linear antenna arrays with low sidelobe level while maintaining the half-power beamwidth of a full linear array. Based on results from existing papers in this field and known approaches to antenna array thinning, a classification of thinning types is introduced. The optimal thinning type for a linear thinned antenna array is determined on the basis of a maximum attainable sidelobe level. The variation of main direction pattern characteristics, such as peak sidelobe level and half-power beamwidth, with respect to a thinning coefficient, are discussed for a number of amplitude tapers.

Optimized LPDA Antenna for IoT Applications

In this new era of fast-growing industry revolution, IoT has become integral part of most industries. In this paper, a high directivity printed log periodic dipole array (LPDA) antenna printed on a FR4 substrate is proposed for the application of IoT communication. The simulation result of NSGA-II optimized antenna is then compared and validated with another optimization scheme, MOEA\\D algorithm. The simulation results demonstrate that the proposed antenna has low sidelobe level of -13.9dB with the VSWR < 2 across the dual bandwidth of 0.3027 GHz and 5.6289 GHz from 4.2166 GHz to 4.5193 GHz and 5.8412 GHz to 11.47 GHz respectively. The proposed antenna has achieved a new low side lobe level of -13.9 dB. It is also possesses a wide bandwidth which enhanced from 2.52GHz to the dual bandwidth of 0.3027 GHz and 5.6289 GHz on 4.2166 GHz to 4.5193 GHz and 5.8412 GHz to 11.47 GHz respectively. It has a good realized gain of 8.42dBi with the increment of 1.42dBi after optimization. The multi objective genetic algorithm optimizes the realized gain, directivity, sidelobe level, bandwidth, standing wave ratio of the proposed antenna which is well suited for practical applications in physical layer IoT communication.

Latest Performance Improvement Strategies and Techniques Used in 5G Antenna Designing Technology, a Comprehensive Study.

In the recent era, fifth-generation technology (5G) has not been fully implemented in the realm of wireless communication. To have excellent accessible bandwidth feasibility, and in order to achieve the aims of 5G standards, such as higher data rates and ultrahigh-definition video streaming, the millimeter wave (mmWave) band must be employed. Services with minimal latency and many other features are feasible only in the mmWave spectrum. To avoid numerous communication complexities such as high connection losses, short wavelength, and restricted bandwidth, as well as path-loss challenges in the mmWave range, an antenna with wide bandwidth, high gain, narrow steerable beam, high isolation, low side-lobe levels, and multiband features is required to alleviate these difficulties and meet 5G communication standards. To overcome these challenges, specific strategies and techniques should be employed in the traditional antenna designing procedure to excellently improve the performance of the antenna in terms of bandwidth, gain, and efficiency and to reduce the mutual coupling effect between the closely colocated antenna elements in MIMOs and arrays. The researchers reported on a variety of bandwidth and gain improvement approaches. To gain broader coverage, traditional antenna design techniques must be modified. In this study, the latest state-of-the-art work is reviewed, such as the role of the metamaterials (MMTs), parasitic patches, hybrid feeding, EBG structure, impact of the slots with different geometrical shapes in the radiator to achieve the goal of wide bandwidth, boosted gain, reduced side-lobes level, as well as stable radiation properties. Mutual coupling reduction techniques are also briefly reported. The role of reconfigurability is focused on in this study, and at the end, the future challenges in the field of antenna design and possible remedies to such issues are reviewed.

60-GHz Double-Layer Transmitarray Antenna Using Complementary Structure

Abstract—A novel double-layer transmitarray element is presented at 60 GHz with linearly- and circularly-polarized characteristics. A planar frequency-selective structure using the complementary design is adopted to augment the element performance for millimeter-wave applications. By integrating two different types of structure, i.e. cross and slot type, the compensation phase range is extended effectively with a satisfactory transmission magnitude. A transmitarray prototype is fabricated and tested to verify this double-layer complementary design. The measured gain at 60.5 GHz is 33.1 dBi with an aperture efficiency of 42.15%. Low side-lobe and cross-polarization levels are obtained. The proposed double-layer complementary design can reduce the structure complexity effectively and offer a high aperture efficiency at a low cost, which can be a potential candidate for the millimeter-wave transmitarray.

Range–Angle Transceiver Beamforming Based on Semicircular-FDA Scheme

Incontrast to the steady angle-dependent transmit beampattern of the conventional phased array, the counterpart of a frequency diverse array (FDA) is basically time variant and range–angle coupled, which limits its potential application in many scenarios. In this article, we consider the beamforming in joint transmit and receive domains to handle the time-variant problem and propose a novel range–angle transceiver beamforming approach based on the semicircular-FDA scheme. In particular, the transceiver scheme of semicircular-FDA is first established.In the sequel, the periodicities of its transceiver beampattern in range and angle dimensions are briefly analyzed. Based on this analysis, a semicircular-FDA applied with nonlinearly increasing frequency offset (NIFO), termed as NIFO semicircular-FDA, is proposed to achieve the beampattern with a single mainlobe peak in range–angle space. Then, an optimization problem is constructed based on an advanced bat algorithm to further reduce the sidelobe level (SLL) of the NIFO semicircular-FDA. Numerical results show that focused time-invariant beampattern with low SLL in both range and angle dimensions can be achieved with the proposed approach.

Wideband and High-Gain Substrate Integrated Folded Horn Fed Open Slot Antenna

This article presents a novel substrate-integrated folded horn-fed open slot antenna with wide bandwidth and high gain for millimeter-wave (mmW) applications. The antenna has a three-layer planar structure, including a pair of open slot radiators and two substrate-integrated H-plane horns (SIHs) that are incorporated as the feed to generate quasi-TEM wave excitations. A folded SIH structure is introduced, which reduces the antenna size by 37%. To improve the gain and radiation patterns, the proposed antenna is designed with differentially fed excitations. The measured results validate that the antenna achieves a wide impedance bandwidth of 54.4% from 52.3 to 91.4 GHz and a peak gain of 16.3 dBi. Meanwhile, the radiation patterns are stable throughout the operating bandwidth with low cross-polarization, sidelobe, and back lobe levels. The proposed wideband, high-gain, planar, and low-cost antenna is an attractive candidate for mmW applications.

Low-Sidelobe Shaped-Beam Pattern Synthesis With Amplitude Constraints

The article deals with the low-sidelobe shaped-beam pattern synthesis (SBPS) problem under amplitude constraints, including the controllable dynamic range ratio (DRR) and the predetermined excitation amplitude. The formulated problem is nonconvex owning to the existing nonconvex constraints. To this end, a set of auxiliary variables are introduced to reformulate the original problem, and then a double-loop iterative algorithm based on the penalty dual decomposition method (PDD) framework is proposed. The proposed approach solves the reformulated problem by updating primal variables with block successive upper-bound maximization (BSUM) algorithm in the inner loop and updating the dual variables and penalty parameter with the constraint violation strategy in the outer loop. One important advantage of the proposed approach is that all of its subproblems have closed-form solutions, which guarantees that the reformulated problem can be effectively solved. Numerical simulations are carried out to validate the proposed approach’s superiority with both isotropic element pattern and active element pattern (AEP). The results show that the proposed approach can obtain a lower sidelobe level (SLL) and a smaller DRR when compared with the state-of-the-art approaches.

Unequally Spaced Antenna Array Synthesis Using Accelerating Gaussian Mutated Cat Swarm Optimization

Low peak sidelobe level (PSLL) and antenna arrays with high directivity are needed nowadays for reliable wireless communication systems. Controlling the PSLL is a major issue in designing effective antenna array systems. In this paper, a nature inspired technique, namely accelerating Gaussian mutated cat swarm optimization (AGMCSO) that attributes global search abilities, is proposed to control PSLL in the radiation pattern. In AGM-SCO, Gaussian mutation with an acceleration parameter is used in the position-updated equation, which allows the algorithm to search in a systematic way to prevent premature convergence and to enhance the speed of convergence. Experiments concerning several benchmark multimodal problems have been conducted and the obtained results illustrate that AGMCSO shows excellent performance concerning evolutionary speed and accuracy. To validate the overall efficacy of the algorithm, a sensitivity analysis was performed for different AGMCSO parameters. AGMCSO was researched on numerous linear, unequally spaced antenna arrays and the results show that in terms of generating low PSLL with a narrow first null beamwidth (FNBW), AGMCSO outperforms conventional algorithms.

Lower sidelobe phased array based on pattern reconfigurable elements

Pattern reconfigurable phased-array antennas can implement the function of beam control and overcome the limited scanning angle of traditional phased-array antennas without affecting the performance and operating frequency. In this article, a linear 1 × 4 phased-array designed for wide-angle scanning is presented. The unit includes an improved C-type dipole antenna, an I-typed resonator, and a ground. With the help of PIN diodes, the direction of the current on the patch is changed so that the unit can operate in two modes. The designed array has the advantages of a simple bias network, wide-beam scanning coverage, high gain, and low-sidelobe levels. Measurement results show that 2.85–3.66 GHz continuous beam scanning has been achieved in the range of −58° to 58°. Meanwhile, gain of up to 11 dBi is obtained, as well as in very good agreement with simulation. The results also verify the reconfigurability of the pattern and the feasibility of the design.

An Efficient Recursive Multibeam Pattern Subtraction (MPS) Beamformer for Planar Antenna Arrays Optimization

In this paper, a new beamforming technique for planar two-dimensional arrays is proposed for optimizing the sidelobe levels (SLLs) by using recursive multibeam pattern subtraction (MPS) technique. The proposed MPS beamformer is demonstrated and its convergence to lower SLL values is investigated and controlled. The performance analysis has shown that the proposed MPS beamformer can effectively reduce the SLL down to less than −50 dB relative to the mainlobe level utilizing the major sidelobes information in the radiation pattern. In addition, the proposed MPS beamformer can be applied to any planar array geometry such as rounded corners rectangular arrays provided that the original array pattern contains sidelobe peaks. The comparison with recent related techniques has shown that the proposed beamformer provides faster convergence time. On the other hand, the proposed technique provides lower sidelobe levels which cannot be achieved by efficient tapering windows for planar two-dimensional arrays. Finally, the scanning performance of the proposed MPS beamformer is demonstrated and the simulation results show solid and consistent SLL levels over the whole angular range from the broadside to endfire directions of the array.

Low-Cost inhomogeneous material for Low-RCS reflectarray antenna implementation

We study a Double-Screen Frequency Selective Surface (DSFSS) mounted on a low-cost inhomogeneous material to design a low Radar Cross Section (RCS) Reflectarray Antenna (RA). Such a DSFSS is a double-sided metallic grating included sub-wavelength cross-shaped patches printed on a porous substrate. Such an artificial substrate is a periodic material made of two alternating dielectrics. The unit cell of such a periodic structure is firstly analyzed by using Method of Moments (MoM). It is shown that DSFSS is a frequency filter with band-stop behavior. Then, such a unit cell is employed to design a single-layer RA. In its design, a phase synthesis approach is applied to optimize the radiation performance of the resultant RA in X-band. Numerical results demonstrate that out-of-band RCS of the designed RA is significantly reduced and the bandwidth of RA is broadened with lower Side Lobe Level (SLL). To validate the obtained results, the designed RA is fabricated and measured. The simulated and experimental results show the proposed low-cost RA has a pencil-beam radiation pattern from 8.7 ∼ 12.3 GHz with maximum gain 26.7dBi at 10.5 GHz, and two RCS reduction bands with the fractional bandwidth 200% (in lower band) and 70% (in upper band).