scholarly journals New Side Lobe Cancellation Method of Linear Frequency Modulated Radar Signals

2020 ◽  
Vol 9 (4) ◽  
pp. 1275-1279
Keyword(s):  
Pulse Compression ◽  
Matched Filter ◽  
Roc Curves ◽  
Side Lobe ◽  
Radar Detection ◽  
Operating Characteristics ◽  
Detection Capability ◽  
Linear Frequency ◽  
Optimum Filter ◽  
Long Pulse

Pulse Compression (PC) technique has many advantages in signal processing of radar systems which enhances the radar performance. For a long pulse, the range detection capability can be increased with PC while maintain the advantage of resolution in range for uncompressed pulse. There are many PC techniques such as Binary and Linear Frequency Modulation (LFM) Codes, which can be utilize in radar. The radar detection performance is affected by unwanted signals, which called side lobes that may mask the weaker useful signals, which are present near to strong signals. Pulse compression that uses LFM code is discussed and contrasted with matched filter keep tracked of Hamming windowing filter technique to eliminate the level effect of side lobes. In the present paper, a proposed optimum filter is introduced to enhance both the radar detection capability and resolution in range. The proposed optimum filter representation is evaluated and compared with the classical matched filter response associated with Hamming windowing filter according to the representation of radar detection through Receiver Operating Characteristics (ROC) curves and resolution performance.

scholarly journals Optimization of two-stage NLFM signal using Heuristic approach

2020 ◽  
Vol 13 (44) ◽  
pp. 4465-4473
Author(s):  
Chandu Kavitha ◽  
Keyword(s):  
Optimization Algorithm ◽  
Frequency Modulation ◽  
Pulse Compression ◽  
Piecewise Linear ◽  
Side Lobe ◽  
Linear Frequency Modulation ◽  
Main Lobe ◽  
Design And Optimization ◽  
Linear Frequency ◽  
Scripting Language

Background/Objectives: The design of appropriate Non-Linear Frequency Modulation (NLFM) signals continues to be the focus of research in radar pulse compression theory for sidelobe reduction. This study focuses on a heuristic design and optimization algorithm to optimize the side lobe values of the NLFM signal designed using two-piece wise linear frequency modulation (LFM) functions. Methods: 1) Heuristic search identifies the optimum B1, T1, and B2, T2, which yield the lowest sidelobe value of the designed function.2) Compute all the side lobe values of the designed NLFM signal using an algorithm developed in Python scripting language. To plot a complete contour map for all the calculated side lobe values, which helps identify the associated variations in the range of side lobe values. Finally, optimize the side lobe values keeping the main lobe width and time-bandwidth (BT) product unchanged by designing a dynamic optimization algorithm. Findings: The algorithm developed considered all side lobe levels after the main lobe for optimization. The focus is mainly on the peak sidelobe ratio (PSLR) value without affecting the other parameters. The results demonstrate that the achieved side lobes exhibit their desired levels. Novelty: The method is useful in all types of hardware associated with weather radar applications to military solutions. The technique can be extended to other multistage signals consisting of piecewise linear Segments. Keywords: Contour; LFM; NLFM; optimization; PSLR

scholarly journals Convolutional Windows for Side Lobe Reduction

2019 ◽  
Vol 8 (10) ◽  
pp. 3526-3529
Keyword(s):  
Frequency Modulation ◽  
Pulse Compression ◽  
Side Lobe ◽  
Linear Frequency Modulation ◽  
Side Lobe Level ◽  
Chirp Signal ◽  
Sidelobe Level ◽  
Linear Frequency ◽  
Radar Systems ◽  
Window Functions

A lot of applications in radar systems necessitate low range side-lobe performance which is achieved by pulse compression processing. Linear Frequency Modulation (LFM) signal is mainly used chirp signal for this processing. The paramount drawback in LFM is the first side-lobe level of -13dB at the receiver side. In this paper, LFM signal is modified by using simple two-stage piece wise linear frequency modulation (PWLFM) functions. The autocorrelation function of this PWLFM signal exhibited low peak sidelobe level ratio (PSLR) value compared to its counterpart LFM signal. An attempt is made to further reduce the side lobe values by using novel Convolutional windows. The simulation results confirm a significant side lobe reduction by the LFM signal designed using PWLFM functions when a more flexible Power of Cosine window function is applied compared to all other window functions.

scholarly journals Encoded Hybrid PSK/FSK Waveform for LPI Radar

2020 ◽  
Vol 8 (6) ◽  
pp. 2753-2760
Keyword(s):  
Frequency Modulation ◽  
Pulse Compression ◽  
Average Power ◽  
Side Lobe ◽  
Linear Frequency Modulation ◽  
Coincidence Detection ◽  
Side Lobe Level ◽  
Linear Frequency ◽  
Non Linear ◽  
Radar Waveforms

Since the advantage of pulse compression radar, the pseudo random codes and poly time codes and non linear frequency modulation has been mostly widely used low probability intercept (LPI) radar waveforms. By changing frequencies time to time in frequency modulation known as non-linear frequency modulation (frequency hopping (FH)), peak to side lobe ratio (PSLR) can be achieved to make less severe the covering effect of nearby targets and to improve the useful dynamic range. Adding an appropriate binary encoded ternary phase shift signal (PSK) as form as Binary encoded Hybrid-PSK/FSK (BEH PSK/FSK), the peak side lobe ratios are obtained very low values (e.g., PSLR<-70dB), similar to the antenna side lobes. In advanced microwave power amplifier technology, now a day’s using low peak to average power modules requires them to be amalgamated at the radio frequency (RF) stage in that way to obtain the required emitted radiated power. The deterministic waveforms are represents Noise waveform radar technology is a valid alternative. The pseudorandom waveform-realization of a noise process, the higher its bandwidth-time (or BT) product, the lower the (numerical) peak side lobe ratio. With practical Bandwidth-time values, the achievable peak side lobe using pure random is not sufficient the generated pseudorandom waveforms undergoes optimized genetic algorithm Hamming Scan (HS) to achieve optimized pseudo random (OBC), in order to achieve the desired side lobe level. This manuscript proposes a general analysis of the two modes of radar waveforms, i.e., Ternary and Binary alphabetic waveforms of coincidence detection.

The Effect of Pulse Compression Chirp Parameters on Profilometry Information and Resolution

2018 ◽  
Author(s):  
Zuwen Sun ◽  
Natalie Baddour
Keyword(s):  
Pulse Compression ◽  
Imaging System ◽  
Matched Filter ◽  
Signal To Noise Ratio ◽  
Imaging Systems ◽  
Center Frequency ◽  
Matched Filtering ◽  
Linear Frequency ◽  
Recent Developments ◽  
Correlation Process

Recent developments in imaging systems have seen the implementation of a radar matched-filtering approach. The goal of the imaging system is to obtain information about an unknown object embedded in the system, by controlling the parameters of the input and measuring the response to the known input. The main merit of using matched filtering in imaging systems is the improvement of Signal to Noise Ratio (SNR). However, the correlation process used in matched filtering may result in a loss of resolution. One way to compensate for lost resolution is via pulse compression. Linear frequency modulated sinusoidal waveforms (chirps) have the property of pulse compression after correlation. Hence, both SNR and resolution can be enhanced by matched-filtering and pulse compression with a chirp. However, the theory behind the effect of chirp parameters on resolution is still not clear. In this paper, a one-dimensional theory of matched-filter imaging with a pulse compressed linear frequency modulated sinusoidal chirp is developed. The effect of the chirp parameters on the corresponding signal is investigated, and guidelines for choosing the chirp parameters for resolution considerations are given based on the developed theory and simulations. The results showed that by manipulating the center frequency, bandwidth, and duration of the chirp, the resolution can be easily enhanced.

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

Sensors ◽  
2021 ◽  
Vol 21 (11) ◽  
pp. 3835
Author(s):  
Ahmed Azouz ◽  
Ashraf Abosekeen ◽  
Sameh Nassar ◽  
Mohamed Hanafy
Keyword(s):  
Cross Sections ◽  
Software Defined Radio ◽  
Pulse Compression ◽  
Matched Filter ◽  
Linear Frequency ◽  
Radar Cross Sections ◽  
Operational Characteristics ◽  
Computational Speed ◽  
Iteration Methods ◽  
The Mathematical Model

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.

Simulation Research on how to Improve the Range Resolution of Pulse Compression Radar Based on Phase Coding

2011 ◽  
Vol 143-144 ◽  
pp. 634-638 ◽  
Author(s):  
Yu Tang
Keyword(s):  
Compression Ratio ◽  
Pulse Compression ◽  
Matched Filter ◽  
Side Lobe ◽  
Radar System ◽  
Radar Signal ◽  
Pulse Modulation ◽  
Range Resolution ◽  
Set Up ◽  
Barker Codes

Phase coded radar signal is one of the pulse-pulse modulation signal in the radar system. Based on the characteristics of matched filtering, we theoretically analyze the basic principle of the phase coded compression radar system. In the Matlab platform, we set up a simulation model which is used for matching filter, when the radar transmitting signal is Barke code signal. The simulation results show that Echo signal can obtain certain pulse compression ratio. By the matched filter, the main lobe amplitude of 13 bits Barker code signal is 22 times the rate of side-lobe. 13 bits Barker codes by the matched filter have the maximum pulse compression ratio.

scholarly journals Modified PWNLFM Signal for Side-Lobe Reduction

2018 ◽  
Vol 7 (4.20) ◽  
pp. 4
Author(s):  
N. Adithya valli ◽  
Dr. D. Elizabath Rani
Keyword(s):  
Linear Function ◽  
Frequency Modulation ◽  
Pulse Compression ◽  
Weighting Function ◽  
Side Lobe ◽  
Linear Frequency Modulation ◽  
Side Lobe Level ◽  
Chirp Signal ◽  
Linear Frequency ◽  
Non Linear

Many applications in radar systems require low range side-lobe performance which is achieved by pulse compression processing. Most used chirp signal for this processing is linear frequency modulation (LFM) signal but with a presence of first high side-lobe level. Suppression of this side-lobe requires weighting function causing the reduction in signal to noise ratio at the receiver owing to mismatch loss. Non-linear chirp signals are introduced as a solution and became most practiced signals aimed at reducing side-lobes. In this paper, an overall piece wise non-linear frequency modulation chirp signal is designed by merging two stages, one with linear function and the other with a tangent based non-linear function. Simulation results show significant reduction in the sidelobe level of autocorrelation function when NLFM is generated in this method. 

Conscious access to fear-relevant information is mediated by threshold

2011 ◽  
Vol 42 (2) ◽  
pp. 56-64 ◽  
Author(s):  
Remigiusz Szczepanowski
Keyword(s):  
Present Report ◽  
Intrinsic Property ◽  
Roc Curves ◽  
Relevant Information ◽  
Perceptual Processing ◽  
High Threshold ◽  
Operating Characteristics ◽  
Emotional Perception ◽  
Fearful Faces ◽  
The Subject

Conscious access to fear-relevant information is mediated by thresholdThe present report proposed a model of access consciousness to fear-relevant information according to which there is a threshold for emotional perception beyond that the subject makes hits with no false alarm. The model was examined by having the participants performed a confidence-ratings masking task with fearful faces. Measures of the thresholds for conscious access were taken by looking at the receiver operating characteristics (ROC) curves generated from a three-state low- and high-threshold (3-LHT) model by Krantz. Indeed, the analysis of the masking data revealed that the ROCs had threshold-like-nature (a two-limb shape) rather continuous (a curvilinear shape) challenging in this fashion the classical signal-detection view on perceptual processing. Moreover, the threshold ROC curve exhibited the specific y-intercepts relevant to conscious access performance. The study suggests that the threshold can be an intrinsic property of conscious access, mediating emotional contents between perceptual states and consciousness.

scholarly journals Cloud Detection Based on High Resolution Stereo Pairs of the Geostationary Meteosat Images

2020 ◽  
Vol 12 (3) ◽  
pp. 371 ◽  
Author(s):  
Sahar Dehnavi ◽  
Yasser Maghsoudi ◽  
Klemen Zakšek ◽  
Mohammad Javad Valadan Zoej ◽  
Gunther Seckmeyer ◽  
...  
Keyword(s):  
High Resolution ◽  
Matched Filter ◽  
Stereo Pair ◽  
Cloud Detection ◽  
Operating Characteristics ◽  
Detection Techniques ◽  
Infrared Imager ◽  
Detection Approach ◽  
Considerable Impact ◽  
Image Pairs

Due to the considerable impact of clouds on the energy balance in the atmosphere and on the earth surface, they are of great importance for various applications in meteorology or remote sensing. An important aspect of the cloud research studies is the detection of cloudy pixels from the processing of satellite images. In this research, we investigated a stereographic method on a new set of Meteosat images, namely the combination of the high resolution visible (HRV) channel of the Meteosat-8 Indian Ocean Data Coverage (IODC) as a stereo pair with the HRV channel of the Meteosat Second Generation (MSG) Meteosat-10 image at 0° E. In addition, an approach based on the outputs from stereo analysis was proposed to detect cloudy pixels. This approach is introduced with a 2D-scatterplot based on the parallax value and the minimum intersection distance. The mentioned scatterplot was applied to determine/detect cloudy pixels in various image subsets with different amounts of cloud cover. Apart from the general advantage of the applied stereography method, which only depends on geometric relationships, the cloud detection results are also improved because: (1) The stereo pair is the HRV bands of the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) sensor, with the highest spatial resolution available from the Meteosat geostationary platform; and (2) the time difference between the image pairs is nearly 5 s, which improves the matching results and also decreases the effect of cloud movements. In order to prove this improvement, the results of this stereo-based approach were compared with three different reflectance-based target detection techniques, including the adaptive coherent estimator (ACE), constrained energy minimization (CEM), and matched filter (MF). The comparison of the receiver operating characteristics (ROC) detection curves and the area under these curves (AUC) showed better detection results with the proposed method. The AUC value was 0.79, 0.90, 0.90, and 0.93 respectively for ACE, CEM, MF, and the proposed stereo-based detection approach. The results of this research shall enable a more realistic modelling of down-welling solar irradiance in the future.

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