Sidelobe Reduction Research Articles

Optimal Mismatched Filter Design by Combining Convex Optimization With Circular Algorithm

Mismatched filters (MMF) have been intensively explored for linear-frequency modulation (LFM) waveform sidelobe reduction. Unlike other design strategies, the use of convex optimization (CO) techniques is able to find the optimal design. However, existing studies for CO-based MMF design have focused on minimizing peak sidelobe level (PSL), which might not take the mainlobe widening sacrifice into account. To address this issue, this paper proposes a weighted CO model targeting a flexible tradeoff between sidelobe suppression and mainlobe widening. Moreover, to better control the optimization problem via the presented CO model, the cyclic algorithm (CA) is employed to determine upper limits on mainlobe width. Consequently, the proposed tradeoff MMF design by combining CA with CO would be feasible to meet the requirements of different target detection scenarios. Comprehensive simulations have been carried out to demonstrate the effectiveness of our presented MMF design.

A review on optimization of antenna array by evolutionary optimization techniques

PurposeOptimization involves changing the input parameters of a process that is experimented with different conditions to obtain the maximum or minimum result. Increasing interest is shown by antenna researchers in finding the optimum solution for designing complex antenna arrays which are possible by optimization techniques.Design/methodology/approachDesign of antenna array is a significant electro-magnetic problem of optimization in the current era. The philosophy of optimization is to find the best solution among several available alternatives. In an antenna array, energy is wasted due to side lobe levels which can be reduced by various optimization techniques. Currently, developing optimization techniques applicable for various types of antenna arrays is focused on by researchers.FindingsIn the paper, different optimization algorithms for reducing the side lobe level of the antenna array are presented. Specifically, genetic algorithm (GA), particle swarm optimization (PSO), ant colony optimization (ACO), cuckoo search algorithm (CSA), invasive weed optimization (IWO), whale optimization algorithm (WOA), fruitfly optimization algorithm (FOA), firefly algorithm (FA), cat swarm optimization (CSO), dragonfly algorithm (DA), enhanced firefly algorithm (EFA) and bat flower pollinator (BFP) are the most popular optimization techniques. Various metrics such as gain enhancement, reduction of side lobe, speed of convergence and the directivity of these algorithms are discussed. Faster convergence is provided by the GA which is used for genetic operator randomization. GA provides improved efficiency of computation with the extreme optimal result as well as outperforming other algorithms of optimization in finding the best solution.Originality/valueThe originality of the paper includes a study that reveals the usage of the different antennas and their importance in various applications.

Reduction of side lobes in the entire azimuth plane in a planar elliptical array antenna

SummaryA novel synthesis method to reduce the maximum side lobe in the entire azimuth plane and for achieving a desired value of directivity of a concentric elliptical array antenna is addressed in this paper. Three well‐performing meta‐heuristic optimization algorithms, teaching learning‐based optimization (TLBO), symbiotic organism search (SOS), and quantum particle swarm optimization (QPSO), are employed to optimize the cost function and to obtain the desired radiation pattern. Different simulation‐based experiments are performed to obtain the best possible set of angular positions and the distribution of isotropic antennas across the ellipses by rigorously maintaining non‐overlapping constraints. The major benefit of the proposed design is the deprecation of interference in all phi planes. The statistical analysis of the simulation results demonstrate perceptible improvement compared with that of a uniformly spaced concentric elliptical array and hence show the efficiency of the proposed algorithms. In both simulation studies, the results obtained using TLBO, SOS, and QPSO are compared. Analysis of the results exhibits that for the stated objective, the TLBO‐ and SOS‐based side lobe reduction approach performs superior to QPSO method. Proposed multi‐objective research work could lead to reduce payload and can simultaneously achieve isoflux coverage in entire azimuth plane on the earth surface which can essentially be utilized in (Low Earth Orbit) LEO and (Geostationary Earth Orbit) GEO satellites applications.

Combined Sidelobe Reduction and Omnidirectional Linearization of Phased Array by Using Tapered Power Amplifier Biasing and Digital Predistortion

Power amplifier (PA) efficiency and linearity are among the key drivers to reduce energy consumption while enabling high data rates in the fifth-generation (5G) millimeter-wave phased array transmitters. Analog per-branch phase and amplitude control is used to steer the beam, suppress the sidelobes, and form zeros to the desired spatial directions. The amplitude control of individual PA inputs makes nonlinearity vary from antenna to antenna, which challenges the common digital predistortion (DPD) used to linearize the array. In this article, we implement an amplitude control for beamforming by tuning the PA gate bias. Varying the output powers via PA biasing makes the nonlinear characteristics observed at the individual PA outputs similar that helps the array DPD to linearize also individual PAs. The technique is validated by both simulations and measurements. As a measurement platform, we use a 28-GHz phased array transceiver equipped with 64 antenna elements and 16 radio frequency chains. The desired beam shape is synthesized by controlling the per-antenna over-the-air-power with PA gate bias. Then, the system is linearized by training DPD with a reference antenna. The DPD is demonstrated with 100-MHz-wide 5G new radio modulated waveform. The best example case showed −23.5-dB maximum sidelobe level (SLL) with 4.9% error vector magnitude and −40.8-dB total radiated adjacent channel power ratio with DPD. The proposed approach enables simultaneous reduction of beam pattern SLL, achieves good linearity in all directions, and maintains the PA efficiency.

A New Optimization Algorithm Based on the Fungi Kingdom Expansion Behavior for Antenna Applications

This paper presents a new optimization algorithm based on the behavior of the fungi kingdom expansion (FKE) to optimize the radiation pattern of the array antenna. The immobile mass expansion of the fungi is mimicked in this work as a chaotic behavior with a sinusoidal map function, while the mobile mass expansion is realized by a linear function. In addition, the random germination of the spores is utilized for randomly distributing the variables that are far away from the best solution. The proposed FKE algorithm is applied to optimize the radiation pattern of the antenna array, and then its performance is compared with that of some well-known algorithms. The MATLAB simulation results verify the superiority of the proposed algorithm in solving 20-element antenna array problems such as sidelobe reduction with sidelobe ratio (SLR = 25.6 dB), flat-top pattern with SLR = 23.5 dB, rectangular pattern with SLR = 19 dB, and anti-jamming systems. The algorithm also results in a 100% success rate for all of the mentioned antenna array problems.

Compact 2D serpentine optical phased array.

We present a two-dimensional (2D) Si photonics optical phased array (OPA) using a serpentine design which eliminates the long directional couplers used in many 2D OPA designs. It significantly reduces the distance between the antenna benefitting far-field sidelobe reduction while maintaining high optical power use efficiency.

Development and Analysis of New NLFM Waveform for Achieving Sidelobe Reduction and Narrowing of Main lobe Width

Aimed at narrowing main lobe width and reduced sidelobe values, we developed three new NLFM chirp waveforms. The ambiguity function and the impact of sampling rate and compression ratios of these waveforms are analyzed. Their performance is examined against the doppler effect and background noise. One of the three designed NLFM chirp waveforms is useful in applications requiring side lobes of -50 dB and narrow main lobe width. The new waveform could achieve reduced sidelobes and narrow main lobe width compared to LFM and other NLFM waveforms

Enhancing image quality of single-frequency microwave imaging with a multistatic full-view array based on sidelobe reduction.

Single-frequency microwave imaging can be effectively realized with multistatic full-view arrays, offering great potential in various sensing applications. In this paper, we address the problem of forming high quality images with the focus on multistatic full-view arrays. We aim to enhance its image quality by means of reducing the side-lobe level (SLL) of the imaging array. K-space representation and PSF analysis are presented to get an insight into the effect of low spatial frequency samples collected by the array on the side-lobe response of the array. Based on this understanding, a novel SLL reduction method is proposed based on weakening the effect of low spatial frequency samples. A modified back-projection algorithm is suggested to apply the proposed SLL reduction method in image reconstruction. Numerical simulations confirm a reduction of about 5 dB in side-lobe level. The functionality of the proposed method is verified by using the experimental measurement data of two different targets. Image quality is enhanced by 3.5 and 4.5 dB in terms of signal-to-mean ratio (SMR) for the two studied targets. This considerable improvement has resulted in avoiding appearance of artifacts and wrong interpretations of the target under imaging. The proposed method can be beneficial for existing imaging systems that utilize a full-view multistatic array, from medical to industrial applications.

Design and Implementation of an Enhanced Matched Filter for Sidelobe Reduction of Pulsed Linear Frequency Modulation Radar.

Pulse compression techniques are commonly used in linear frequency modulated (LFM) waveforms to improve the signal-to-noise ratios (SNRs) and range resolutions of pulsed radars, whose detection capabilities are affected by the sidelobes. In this study, a sidelobe reduction filter (SRF) was designed and implemented using software defined radio (SDR). An enhanced matched filter (EMF) that combines a matched filter (MF) and an SRF is proposed and was implemented. In contrast to the current commonly used approaches, the mathematical model of the SRF frequency response is extracted without depending on any iteration methods or adaptive techniques, which results in increased efficiency and computational speed for the developed model. The performance of the proposed EMF was verified through the measurement of four metrics, including the peak sidelobe ratio (PSLR), the impulse response width (IRW), the mainlobe loss ratio (MLR), and the receiver operational characteristics (ROCs) at different SNRs. The ambiguity function was then used to characterize the Doppler effect on the designed EMF. In addition, the detection of single and multiple targets using the proposed EMF was performed, and the results showed that it overcame the masking problem due to its effective reduction of the sidelobes. Hence, the practical application of the EMF matches the performance analysis. Moreover, when implementing the EMF proposed in this paper, it outperformed the common MF, especially when detecting targets moving at low speeds and having small radar cross-sections (RCS), even under severe masking conditions.

Low side-lobe level pattern synthesis of optical leaky-wave antennas

It is well-known that the reduction of side lobes is important for decreasing interference with components in an optical system, as well as obtaining high information security and lowering power losses. This paper introduces a procedure, based on the simultaneous control of the phase and leakage constants, through which the side-lobe level (SLL) of an optical leaky-wave antenna (OLWA) can be controlled. The synthesis procedure is portrayed using a low SLL conventional OLWA i.e., grating waveguide (GWG). The standard telecommunication wavelength of 1550 nm is considered as the operating wavelength. The simulation results confirm the accuracy of the design procedure. According to the results, the antenna has a low SLL of − 29 dB and a high gain of 26 dBi. The reflection coefficient of the resulting antenna, − 31 dB at the design wavelength, makes the antenna suitable for optical wireless communications.

Side Lobe Reduction Using Non-Uniform Linear Phased Arrays

Non-uniform amplitude excitation arrays are nowadays very desirable in the modern wireless communication systems. They have ability to provide required radiation characteristics such as low side lobes and good directivity. The uniform amplitude excitation arrays are good in providing good directivity and narrow beam width. However, these desired radiation features are come at the cost of relatively high side lobes. Thus, these types of arrays are not widely used in the wireless communication systems especially when these arrays are operated in a noisy and crowded environment that contains many interfering signals. Non-uniform amplitude excitations such as Dolph and Taylor are considered in this paper and their performances are investigated under various array parameters. Simulation results show that as the amplitude excitations of the array elements decaying at the edge elements more reduction in the sidelobe patterns can be obtained.

Minimum Variance Combined With Modified Delay Multiply-and-Sum Beamforming for Plane-Wave Compounding.

Plane-wave compounding is an active topic of research in ultrasound imaging because it is a promising technique for ultrafast ultrasound imaging. Unfortunately, due to the data-independent nature of the traditional compounding method, it imposes a fundamental limit on image quality. To address this issue, adaptive beamformers have been implemented in the compounding procedure. In this article, a new adaptive beamformer for the 2-D data set obtained from multiple plane-wave transmissions is investigated. In the proposed scheme, the minimum variance (MV) weights are applied to the backscattered echoes. Then, the final image is obtained by employing a modified version of the delay multiply-and-sum (DMAS) beamformer in the coherent compounding. The results demonstrate that the presented MV-DMAS scheme outperforms the conventional coherent compounding in both terms of resolution and contrast. It also offers improvements over the 2-D-DMAS and some MV-based methods presented in the literature, such that it achieves at least 20.9% enhancement in sidelobe reduction compared with the best result of MV-based methods. Also, by the proposed method, the in vivo study shows an improved generalized contrast-to-noise ratio (GCNR) that implies a higher probability of lesion detection.

An improved peak side lobe reduction method for linear array antenna for military applications

PurposeThe purpose of this paper is to improve energy efficiency and further reduction of side lobe level the algorithm proposed is firework algorithm. In this paper, roused by the eminent swarm conduct of firecrackers, a novel multitude insight calculation called fireworks algorithm (FA) is proposed for work enhancement. The FA is introduced and actualized by mimicking the blast procedure of firecrackers. In the FA, two blast (search) forms are utilized and systems for keeping decent variety of sparkles are likewise all around planned. To approve the presentation of the proposed FA, correlation tests were led on nine benchmark test capacities among the FA, the standard PSO (SPSO) and the clonal PSO (CPSO).Design/methodology/approachThe antenna arrays are used to improve the capacity and spectral efficiency of wireless communication system. The latest communication systems use the antenna array technology to improve the spectral efficiency, fill rate and the energy efficiency of the communication system can be enhanced. One of the most important properties of antenna array is beam pattern. A directional main lobe with low side lobe level (SLL) of the beam pattern will reduce the interference and enhance the quality of communication. The classical methods for reducing the side lobe level are differential evolution algorithm and PSO algorithm. In this paper, roused by the eminent swarm conduct of firecrackers, a novel multitude insight calculation called fireworks algorithm (FA) is proposed for work enhancement. The FA is introduced and actualized by mimicking the blast procedure of firecrackers. In the FA, two blast (search) forms are utilized and systems for keeping decent variety of sparkles are likewise all around planned. To approve the presentation of the proposed FA, correlation tests were led on nine benchmark test capacities among the FA, the standard PSO (SPSO) and the clonal PSO (CPSO). It is demonstrated that the FA plainly beats the SPSO and the CPSO in both enhancement exactness and combination speed. The results convey that the side lobe level is reduced to −34.78dB and fill rate is increased to 78.53.FindingsSamples including 16-element LAAs are conducted to verify the optimization performances of the SLL reductions. Simulation results show that the SLLs can be effectively reduced by FA. Moreover, compared with other benchmark algorithms, fireworks has a better performance in terms of the accuracy, the convergence rate and the stability.Research limitations/implicationsWith the use of algorithms radiation is prone to noise one way or other. Even with any optimizations we cannot expect radiation to be ideal. Power dissipation or electro magnetic interference is bound to happen, but the use of optimization algorithms tries to reduce them to the extent that is possible.Practical implications16-element linear antenna array is available with latest versions of Matlab.Social implicationsThe latest technologies and emerging developments in the field of communication and with exponential growth in users the capacity of communication system has bottlenecks. The antenna arrays are used to improve the capacity and spectral efficiency of wireless communication system. The latest communication systems use the antenna array technology which is to improve the spectral efficiency, fill rate and the energy efficiency of the communication system can be enhanced.Originality/valueBy using FA, the fill rate is increased to 78.53 and the side lobe level is reduced to 35dB, when compared with the bench mark algorithms.

Radiation pattern of planar optoelectronic antennas for broadband continuous-wave terahertz emission.

In future wireless communication networks at terahertz frequencies, the directivity and the beam profile of the emitters are highly relevant since no additional beam forming optics can be placed in free-space between the emitter and receiver. We investigated the radiation pattern and the polarization of broadband continuous-wave (cw) terahertz emitters experimentally and by numerical simulations between 100 GHz and 500 GHz. The emitters are indium phosphide (InP) photodiodes with attached planar antenna, mounted on a hyper-hemispherical silicon lens and integrated into a fiber-pigtailed module. As both packaging and material of the emitter was identical for all devices, similarities and differences can be directly linked to the antenna structure. We found that the feeding point structure that connects photodiode and antenna has a large influence on the radiation pattern. By optimizing the feeding point, we could reduce side lobes from -2 dB to -13 dB and narrow the 6dB beam angle from ±14° to ±9° at 300 GHz.

Spatiotemporal Coherence Weighting for In Vivo Cardiac Photoacoustic Image Beamformation.

Photoacoustic (PA) image reconstruction generally utilizes delay-and-sum (DAS) beamforming of received acoustic waves from tissue irradiated with optical illumination. However, nonadaptive DAS reconstructed cardiac PA images exhibit temporally varying noise which causes reduced myocardial PA signal specificity, making image interpretation difficult. Adaptive beamforming algorithms such as minimum variance (MV) with coherence factor (CF) weighting have been previously reported to improve the DAS image quality. In this article, we report on an adaptive beamforming algorithm by extending CF weighting to the temporal domain for preclinical cardiac PA imaging (PAI). The proposed spatiotemporal coherence factor (STCF) considers multiple temporally adjacent image acquisition events during beamforming and cancels out signals with low spatial coherence and temporal coherence, resulting in higher background noise cancellation while preserving the main features of interest (myocardial wall) in the resultant PA images. STCF has been validated using the numerical simulations and in vivo ECG and respiratory-signal-gated cardiac PAI in healthy murine hearts. The numerical simulation results demonstrate that STCF weighting outperforms DAS and MV beamforming with and without CF weighting under different levels of inherent contrast, acoustic attenuation, optical scattering, and signal-to-noise (SNR) of channel data. Performance improvement is attributed to higher sidelobe reduction (at least 5 dB) and SNR improvement (at least 10 dB). Improved myocardial signal specificity and higher signal rejection in the left ventricular chamber and acoustic gel region are observed with STCF in cardiac PAI.

Temporal optical besselon waves for high-repetition rate picosecond sources

We analyse the temporal properties of the optical pulse wave that is obtained by applying a discrete set of spectral π/2 phase shifts to continuous-wave light that is phase-modulated by a temporal sinusoidal wave. We develop an analytical model to describe this new optical waveform that we name ‘besselon’. We also discuss the reduction of sidelobes in the pulse intensity profiles by means of an additional spectral π phase shift, and show that the resulting pulses can be efficiently time-interleaved. The various predicted properties of the besselon are confirmed by experiments demonstrating the generation of low duty cycle, high-quality pulses at repetition rates up to 28 GHz.

Thinned 8 × 8 Planar Antenna Array with Reduced Side Lobe Levels for 5G Applications

The purpose of this work is to investigate three antenna designs using the main element that provides radiation pattern with diminish side lobes and high gain of interest for the fifth generation. Antenna designs comprises: (1) fully filled 8 × 8 planar array (2) optimized thinned planar array and (3) optimized tapered planar array. The main motive is to inactive a few number of elements of a fully filled 8 × 8 array while keeping the gain and return loss undisturbed ensuring the high reduction in sidelobe levels. GA (Genetic Algorithm) is tested to estimate the optimized amalgamation of inactive and active elements corresponding to reduce sidelobe levels. Optimization techniques such as the Thinning and Tapering of the planar array are considered in this study. The performances of all three types of optimized planar antenna arrays which are designed on RT/Duroid 5880 dielectric are investigated through a finite element study using CST MW Studio ver.2018 software operating at the desired 28 GHz frequency. By comparing with a fully filled planar array of equal size, the simulation results unveil that optimized thinned and tapered planar arrays show better performance in terms of future generation aspects.

Spatial-Time Complementary Coding Signal Design for RadCom System

Sharing signal design is an important challenge in radar communication integrated (RadCom) system. In this paper, a spatial-time complementary coding signal design method is proposed. Coding signal generation, radar receive processing and communication receive processing are presented sequentially. Numerical simulation results show that the proposed method achieves better sidelobe reduction than ordinary random coding signals.

Noise Adaptive Beamforming for Linear Array Photoacoustic Imaging

The delay-and-sum (DAS) algorithm is widely used for beamforming in linear array photoacoustic (PA) imaging systems and is characterized by fast execution. However, these algorithms suffer from various drawbacks, such as low resolution, low contrast, high sidelobe artifacts, and lack of visual coherence. More recently, adaptive weighting was introduced to improve the reconstruction image quality. Unfortunately, the existing state-of-the-art adaptive beamforming algorithms are computationally expensive and do not consider the specific noise characteristics of the acquired ultrasonic signal. In this article, we present a new adaptive weighting factor named the variational coherence factor (VCF), which takes into account the noise level variations of radio frequency data. The proposed technique provides superior results in terms of image resolution, sidelobe reduction, signal-to-noise ratio (SNR), and contrast level improvement. The quantitative results of the microsphere phantom imaging show that the proposed VCF-assisted DAS method leads to 55% and 25% improvements in full-width-at-half-maximum (FWHM) and 57% and 32% improvement in SNR, respectively, compared to the state-of-the-art DAS-based methods. The results demonstrate that the proposed method can effectively improve the reconstructed image quality and deliver satisfactory imaging performance even with a limited number of sensor elements. The proposed method can potentially reduce the instrumentation cost of the PA imaging system and contribute toward the clinical translation of the modality.

Spatial Interference Reduction by Subarray Stacking in Large Two-Dimensional Antenna Arrays

This article proposes a systematic approach for stacking uniform linear arrays (ULAs) of different sizes to reduce sidelobes and form nulls to the radiated beam pattern. In sidelobe reduction, the nulls and sidelobes of the vertically stacked ULAs are aligned to reduce the overall sidelobe level (SLL). In nulling, the nulls of varying length ULAs are aligned to configure the null direction and simultaneously reduce the sidelobes. Both approaches are relaxed to ensure the feasibility of the implementation. The stacking methods are studied by an extensive set of simulations together with azimuth and elevation beamforming. A sidelobe reduction method showed potential for better than 30 dB SLL and more than 20 dB relative null depth with less than 100 antenna elements. Finally, the concepts are validated by beam pattern measurements of a 28 GHz 64-element, 16-chain phased-array transceiver using a 100 MHz wide 5G waveform.