Sidelobe Reduction Technique Research Articles

Robust Near-field Circular Beamformer with Artificial Intelligence Based Side-lobe Reduction Technique

Robust Near-field Circular Beamformer with Artificial Intelligence Based Side-lobe Reduction Technique

The Design and Analysis of the Sidelobe Reduction Filter for Polyphase Frank Codes

Long-duration radar signals have a low-range resolution but have high-energy contents, whereas short-duration radar signals have a high-range resolution but have low-energy contents. The pulse compression technique allows the radar signal designers to achieve desired energy corresponding to long-duration signals and range resolution corresponding to short-duration signals simultaneously. The pulse compression technique is used in a high-range resolution radar to discriminate closely located targets in the same vicinity and it also improves radar parameters’ measurement accuracy. Polyphase codes are widely used as pulse compression signals in high-range resolution radar systems. The major disadvantage of pulse compression codes is unwanted correlation sidelobes at the output of the matched filter. This paper proposes the sidelobe reduction technique to reduce the Peak Sidelobes Level (PSL) of Frank polyphase codes. The weights of the proposed Sidelobes Reduction Filter (SRF) are optimized by using the Modified Genetic Algorithm (MGA). The proposed technique reduced autocorrelation peak sidelobe level significantly. Finally, the synthesized results of the proposed SRF are presented in this paper.

Enhancement of Matched Filter Response for Chirp Radar Signals using Signal Recovery Technique

The matched filter is one among many effective techniques used to maximize the signal –to- noise ratio (SNR) of chirp radar signals. Besides this enhancement in SNR, it has a drawback due to sidelobe levels which degrade the filter response. There are many additional techniques which reduce these levels such as window techniques and inverse filter. In this paper, a new approach is utilized to completely cancel the level of matched filter side lobes based on the signal recovery of the compressive sensing (CS) theory. The reconstruction process of CS is based on the CAMP algorithm which applied to the response of the matched filter. The recovered chirp radar signals are achieved with completely side lobes cancellation compared to the traditional side lobe reduction technique based on the widow method. The comparison between the proposed and traditional methods is achieved according to the detection performance using Receiver Operating Characteristic (ROC) curve. Besides the detection performance, a resolution in the range is another comparison aspect between these algorithms.

Waveform performance and sidelobe reduction techniques for continuous active sonar (CAS)

The ability to conduct surveillance and tracking of targets over a wide area necessitates the use of a distributed sensing network and an appropriate processing scheme. One such technique that may be appropriate for the target tracking problem is continuous active sonar (CAS). In September 2016, an experiment was performed in Narragansett Bay, RI, to assess the performance of CAS for tracking a single unmanned underwater vehicle (UUV). PN sequence-coded chirps and LFM pulses of various bandwidths and center frequencies were transmitted from one transducer and received at two hydrophones in different locations. Following the experiment, several range-doppler sidelobe reduction techniques were experimented with to improve target detections and range-doppler estimations. During processing, waveform properties critical to sidelobe reduction performance were identified, and new waveforms have been chosen which exhibit these properties. A new experiment will be conducted in the coming months to demonstrate the performance of these waveforms, and results are expected to show improved detections and range-doppler estimations for various targets.

An efficient side lobe reduction technique considering mutual coupling effect in linear array antenna using BAT algorithm

Abstract This paper presents an investigation of mutual coupling effect among the array elements in a symmetric linear array antenna with the aim of reducing the side lobe level and the null control for the radiation pattern synthesis using BAT Algorithm. PSO and DE optimization techniques are also adopted for the sake of comparison and to prove the superiority of BAT algorithm based design. Reduced side lobe level and null control, with and without considering the mutual coupling effect in the cost function have been achieved by an optimum perturbation of the array elements' current excitation amplitude weights and the inter-element spacing among the array elements. The results are also compared with those of a uniform reference array having equal number of elements with λ 2 inter-element spacing. The approach proposed in this paper is a generic one and can be easily applied to any type of symmetrical linear arrays having any number of elements. Five different design examples are presented and their performances are studied to illustrate the capability of BAT algorithm based approach over those of PSO and DE.

A Study on Sidelobe Analysis and Reduction Technique in Azimuth for Forward-Looking Imaging Radar

A Study on Sidelobe Analysis and Reduction Technique in Azimuth for Forward-Looking Imaging Radar

Dynamic Interference Control in OFDM-Based Cognitive Radio Network Using Genetic Algorithm

In OFDM-based cognitive radio networks, minimizing the interference caused to the primary user (PU) by the substantial amount of out-of-band (OOB) emission is a great challenge. In this paper, we propose a dynamic interference control method using the additive signal side lobe reduction technique and genetic algorithm (GA) in CR-OFDM systems. Additive signal side lobe reduction technique is based on adding a complex array to modulated data symbols in the constellation plane for side lobe reduction in OFDM system. In the proposed method, GA generates optimum additive signal which can effectively reduce the OOB signal interference to the primary system. The GA also strives to keep the interference below a predefined tolerable limit and at the same time it maximizes secondary user's transmission opportunity. The results show that the side lobes of the OFDM-based secondary user signal can be reduced by up to 38 dB and the PU interference tolerable limit can be satisfied at the cost of a minor addition in bit error rate (BER). The results further show that the proposed method delivers better performance as compared to non-GA additive signal method in terms of side lobe reduction as well as BER.

Performance Evaluation of Compound Barker Codes using Cascaded Mismatched Filter Technique

The major advantages of pulse compression are low pulsepower which makes it suitable for solid-state devices, higher maximum range, good range resolution and better jamming immunity. The matched filter is the optimal linear filter for maximizing the signal to noise ratio (SNR) in the presence of additive stochastic noise. Pulse compression is an example of matched filtering. But this matched filter output consists of unwanted but unavoidable side lobes. For multiple-target radar, the side lobes of the compressed pulse must be considered in the system design because of the likelihood of false alarms. At the receiver the signal processor uses weighting filters which are not matched to the transmitted waveform. When this filter is not matched to the transmitted waveform then filter output consists of unwanted but unavoidable side lobes. In this paper a new technique is proposed to suppress the side lobes of radar signals that result from standard matched filtering. This technique produces better peak side lobe ratio than all other conventional side lobe reduction techniques. In simulation the results of this filter technique for compound Barker codes is compared with the other side lobe reduction techniques.

IJARCCE - Computer and Communication Engineering

In this paper, the masked two-dimensional array is modelled and designed to reduce the sidelobe levels at no extra processing or optimization for the elements locations and feedings. The masking will turn off the elements at the four corners with a circular boundary function and results in a redistribution and reduction of the sidelobes at the cost of increasing other negligible sidelobes. The new masked two-dimensional array has the advantage of easy manufacturing compared with the concentric circular arrays while maintaining almost the same sidelobe levels and patterns. The analysis of the proposed masked array shows that the sidelobe levels will be reduced by 4 dB at first sidelobe in the two major sidelobe planes (i.e. θ = 0 o and 90 o ) and is more reduced by up to 10 dB at other sidelobes. In addition, the sidelobe levels can be further reduced by applying any other sidelobe reduction technique as add-on improvement to the array pattern.

Performance Evaluation of Barker Codes using New Pulse Compression Technique

Pulse compression is used to achieve large radiated energy but simultaneously a short pulse for range resolution. Range resolution is an ability of the receiver to detect nearby targets. Pulse compression can also detect small target signals out of clutter. The matched filter output consists of unwanted but unavoidable side lobes however the reduction of this side lobe strength is the active research topic in radar signal processing. In this paper a new technique is proposed to suppress the side lobes of radar signals that result from standard matched filtering. In this technique, it produces better peak side lobe ratio than all other conventional side lobe reduction techniques. In simulation results, the performance of this filter technique for Barker codes is compared with the amplitude shift code side lobe reduction technique.

An excellent reduction in sidelobe level for P4 code by using of a new pulse compression scheme

P4 polyphase code is well known in pulse compression technique. For P4 code with length 1000, peak sidelobe level (PSL) and integrated sidelobe level (ISL) are −36dB and −16dB, respectively. In order to increase the performance, there are different reduction techniques to reduce the sidelobes of P4 code. This paper presents a novel sidelobe reduction technique that reduces the PSL and ISL to −127dB and −104dB, respectively. Also, other sidelobe reduction techniques such as Woo filter are investigated and compared with the novel proposed technique. Simulations and results show that the proposed technique produces a better peak side lobe ratio (PSL) and integrated side lobe ratio (ISL) than other techniques.

Simplified Sidelobe Reduction Techniques for Concentric Ring Arrays

In this paper, a simplified sidelobe reduction technique for uniform concentric circular antenna arrays (UCCA) is proposed. This technique is based on modifying some conventional windows to control the amplitude feeding instead of using adaptive techniques which require excessive processing and calculations and suffer from the lack of practical application especially for UCCA. The modified windows are applied to individual rings of the array that will taper the corresponding current amplitudes. The resulted sidelobe level, beamwidth and stability for amplitude errors are discussed for the different proposed windows where it shows a sidelobe reduction to about 49 dB as in the case of Binomial UCCA while the Hamming window shows the most immunity to tapered amplitude errors.

SIDELOBES LEVEL IMPROVEMENT BY USING A NEW SCHEME USED IN MICROWAVE PULSE COMPRESSION RADARS

P4 polyphase code is well known in microwave pulse compression technique. There are difierent reduction techniques to reduce the sidelobes of P4 code. This paper presents a new sidelobe reduction technique which its results are excellent. To valid our work, other sidelobe reduction techniques such as Woo fllter and modifled forms of Woo fllter are investigated and compared with the technique presented in this paper. Results show that the method introduced in this paper produces better peak side lobe ratio (PSL) and integrated side lobe ratio (ISL) than other solutions.

Aperture-domain processing and its applications in ultrasound imaging: A review

This paper provides a review of advanced algorithms for ultrasound image formation and signal processing that are based on aperture-domain data (i.e. the data recorded by individual channels prior to beam summation). First aperture-domain data are defined and their properties described, then two specific examples of phase-aberration correction and vector velocity estimation are presented. For phase-aberration correction, sidelobe-reduction techniques based on the coherence of the received aperture-domain data were tested with clinical breast data; the mean improvements in the contrast and contrast-to-noise ratios were 6.9 dB and 23.2 per cent, respectively. For flow estimation, a conventional scanner can only estimate the flow velocity parallel to the beam axis. The proposed flow estimation technique uses aperture-domain data for two-dimensional flow-velocity estimation. The experimental results demonstrate that the estimation errors for the proposed technique are 2.18 per cent and 18.11 per cent in the axial and lateral velocity components, respectively. Other applications in which aperture-domain data can be used are also discussed.

SIDELOBES REDUCTION USING SIMPLE TWO AND TRI-STAGES NON LINEAR FREQUENCY MODULATION (NLFM)

The Linear Frequency Modulation (LFM) waveform is the most commonly and extensively used signal in practical radar system. However a compressed LFM signal at the receiver will produce the flrst sidelobe at a level of i13dB to the peak of the main lobe. A weighting function is needed to apply in order to reduce the sidelobes. However, the penalty of mismatch loss is clearly evident. It may reduce output SNR, typically by 1 to 2dB. Every single dB of additional SNR can have great efiects in reducing false alarm rates in target detection applications. In an efiort to achieve low autocorrelation sidelobe level without applying weighting function, Non-Linear Frequency Modulation (NLFM) signal has been investigated. This paper describes the sidelobe reduction techniques using simple two-stage FM waveform, modifled two-stage FM waveform and tri-stage FM waveform. Simulation results of the proposed NLFM signal are presented. Sidelobe reduction of more than i19dB can be achieved by this design without any weighting technique applied.

Spatially Variant Apodization for Squinted Synthetic Aperture Radar Images

Spatially variant apodization (SVA) is a nonlinear sidelobe reduction technique that improves sidelobe level and preserves resolution at the same time. This method implements a bidimensional finite impulse response filter with adaptive taps depending on image information. Some papers that have been previously published analyze SVA at the Nyquist rate or at higher rates focused on strip synthetic aperture radar (SAR). This paper shows that traditional SVA techniques are useless when the sensor operates with a squint angle. The reasons for this behaviour are analyzed, and a new implementation that largely improves the results is presented. The algorithm is applied to simulated SAR images in order to demonstrate the good quality achieved along with efficient computation.

A pair of asymmetric weighting receivers and polyphase codes for efficient aperiodic correlations

Sequences with low autocorrelation levels are highly desirable in digital communication. Conventional sidelobe reduction techniques have suffered from performance degradations in range resolutions and signal-to-noise ratio (SNR) gains. In this paper we propose a way to synthesize amplitude weight correlators for polyphase codes. These weighted codes generate sidelobes that are lower than those found in Barker codes. The sidelobe level is kept uniformly flat over all time delays while the range resolution loss is prevented. Unlike the Barker codes, the proposed technique is not limited by the code length. The technique is easy to implement and incurs a minimal SNR loss.

Development of modified polyphase P codes with optimum sidelobe characteristics

The unique range sidelobe properties of P codes are reviewed and a detailed description of the sidelobe reduction technique is given. Based on this analysis, a novel waveform and corresponding pulse compression filter concept are developed. This new approach achieves a highly improved range-sidelobe reduction effect without increasing the system complexity. It is shown how the peak of the range sidelobe can be kept minimised to the Barker code level on this particular waveform. Simulation results are provided to demonstrate the superior performance of this pulse compression scheme and verify its robustness to various noise sources existing in real environments.

Time sidelobe reduction technique for binary phase coded pulse compression

AbstractA time sidelobe (TSL) reduction technique in binary code pulse compression is proposed. A code with a small peak sidelobe (PSL) is searched. Many codes have been obtained that have much smaller PSL than the conventional binary code with the compression ratio in the range from 5 to 16. Simulations are carried out for some of these codes and the optimum IF filter bandwidth is evaluated. It is confirmed that the waveform is stable for Doppler and the PSL value is kept small. © 2001 Scripta Technica, Electron Comm Jpn Pt 1, 84(12): 52–60, 2001

Sidelobe reduction in optical signal processing

A general procedure is introduced for sidelobe and noise reduction in optical or digital signal processing. Specific examples of sidelobe reduction in imaging are presented. It is demonstrated that the new method provides superior spatial resolution to previously proposed sidelobe-reduction techniques.