Range Pulse Compression Research Articles

Parallel Optimisation and Implementation of a Real-Time Back Projection (BP) Algorithm for SAR Based on FPGA.

This study conducts an in-depth evaluation of imaging algorithms and software and hardware architectures to meet the capability requirements of real-time image acquisition systems, such as spaceborne and airborne synthetic aperture radar (SAR) systems. By analysing the principles and models of SAR imaging, this research creatively puts forward the fully parallel processing architecture for the back projection (BP) algorithm based on Field-Programmable Gate Array (FPGA). The processing time consumption has significant advantages compared with existing methods. This article describes the BP imaging algorithm, which stands out with its high processing accuracy and two-dimensional decoupling of distance and azimuth, and analyses the algorithmic flow, operation, and storage requirements. The algorithm is divided into five core operations: range pulse compression, upsampling, oblique distance calculation, data reading, and phase accumulation. The architecture and optimisation of the algorithm are presented, and the optimisation methods are described in detail from the perspective of algorithm flow, fixed-point operation, parallel processing, and distributed storage. Next, the maximum resource utilisation rate of the hardware platform in this study is found to be more than 80%, the system power consumption is 21.073 W, and the processing time efficiency is better than designs with other FPGA, DSP, GPU, and CPU. Finally, the correctness of the processing results is verified using actual data. The experimental results showed that 1.1 s were required to generate an image with a size of 900 × 900 pixels at a 200 MHz clock rate. This technology can solve the multi-mode, multi-resolution, and multi-geometry signal processing problems in an integrated manner, thus laying a foundation for the development of a new, high-performance, SAR system for real-time imaging processing.

A Clutter Suppression Method Based on NSS-RPCA in Heterogeneous Environments for SAR-GMTI

Clutter background suppression is a critical problem in synthetic aperture radar-ground moving target indication (SAR-GMTI). In general, a great quantity of secondary data is not easily acquired in heterogeneous environments. To solve the problem of clutter suppression, a method based on nonlocal self-similarity-robust principal component analysis (NSS-RPCA) is proposed for airborne SAR systems. First, discrete clutter is separated from the echo data by RPCA after range pulse compression. Second, similar blocks of the residual-clutter background are extracted to overcome the training sample limitation using the NSS method in the 2-D time domain. Third, subcovariance matrices are structured by the similar blocks, and the subcovariance matrix is stacked into a tensor. Then, the subclutter covariance matrix can be obtained from the stacked subcovariance matrix tensor by RPCA, where the residual-clutter tensor is of low rank and the target tensor is sparse. Finally, the residual clutter can be suppressed by the subclutter covariance matrix. In this manner, the source of independent identically distributed (IID) samples will be increased significantly without aperture loss by the proposed method. Simulation and analysis based on the experimental data illustrate the effectiveness of the proposed method.

CZT Algorithm for Multiple-Receiver Synthetic Aperture Sonar

The compensation of slant range motion errors needs to be carried out after range pulse compression in the signal processing of multiple-receiver synthetic aperture sonar (SAS). Whereas range pulse compression cannot be performed as the first step in multiple-receiver SAS chirp scaling (CS) algorithm, as it requires the transmitted signal to be linearly frequency modulated. For this reason, it is difficult to combine CS algorithm with motion compensation. Besides, those imaging algorithms based on interpolation, such as range-Doppler algorithm and wavenumber domain algorithm, have plenty of computation load and large phase errors. Aimed at these problems, a CZT algorithm for multiple-receiver SAS in the non-stop-hop-stop mode is proposed in this paper. The proposed algorithm can correct range cell migration utilizing chirp-z transform, which avoids interpolation. Furthermore, the algorithm is easily combined with motion compensation as it can process pulse-compressed data directly. This paper describes the algorithm in 9 key steps, including the principle of correcting range cell migration utilizing chirp-z transform in discrete domain. In the simulation and sea trial data processing, the proposed algorithm provides image quality equal to the CS algorithm, and the algorithm is slightly more efficient than CS algorithm when combined with motion compensation.

Rapid development of SAR backward projection imaging algorithm based on MATLAB

This paper introduces a kind of FPGA rapid development method to complete the backward projection algorithm of SAR. Firstly, the traditional FPGA development has strict requirements for developers’ software and hardware knowledge. Then we introduce a kind of FPGA rapid development method based on the 2018(a) version of MATLAB’s Simulink of MATLAB. And then, the algorithm is divided into two parts, one is the range pulse compression part, and the other is the backward projection part. In order to make full use of the parallelism of BP algorithm, this paper divides the dates into four parts in the distance direction and the imaging grid is also divided into four parts. The projection grid is still based on the whole grid, which can improve the real-time performance of the algorithm. After the algorithm is modeled in Simulink, the model can be converted to the corresponding FPGA code by using the fixed point tool. The comparison of Scope display results with MATLAB results demonstrates the effectiveness of this MATLAB-based Simulink tool for FPGA development.

In brief

PAGE 1259 Researchers in China have proposed an unconventional dual-band antenna with two transverse slots etched onto a substrate integrated waveguide (SIW) cavity. The design exhibits good stopband characteristics including significantly improved non-radiating gain and band-edge selectivity. Experimental results verify the effectiveness of the antenna and promote its use in wireless communication applications. PAGE 1302 i-vector based speech recognition frameworks require effective channel compensation methods for enlarging class differences while reducing class variations. Using a discriminatively learned network (DLN) a team of Chinese researchers used both speaker classification and supervising verification signals for identification. The DLN performs better than linear discriminant analysis (LDA) methods. Electric field distributions at different frequencies. PAGE 1298 A large collaboration of researchers from the USA and Qatar report the enhancement of electrical characteristics in thin film transistors (TFTs) by stacking layers with alternating precursor solution concentrations. The mobility of the fabricated alternating-layer TFT was higher than those with only single concentrations. Future work will study the underlying reason for this effect. Similar DNN parameter architecture. PAGE 1292 A novel analytical model of polarimetric dispersion (PD) based on frequency-domain range pulse compression has been analysed and proposed by researchers in China. The simulation results indicate that spaceborne P-band ultra-wideband synthetic aperture radar systems are heavily influenced by PD effects from ionospheric Faraday rotation. Field effect mobility of TFTs at different concentrations. PAGE 1260 A simple internal antenna combining a planar inverted F antenna and a loop antenna to achieve wideband ultra-high frequency operation for digital television applications has been presented by researchers in Korea. The antenna is implementable within T models with sufficiently wide bandwidth and high peak gain to provide good performance. Polarimetric distortion coefficient function with bandwidth. 3D structure of proposed loop antenna.

Effects of polarimetric dispersion on future spaceborne P‐band ultra‐wideband SAR

Spaceborne synthetic aperture radar (SAR) polarimetric application, operating at P-band, is significantly influenced by ionospheric Faraday rotation (FR). Various researches have been published to evaluate the FR effect on polarimetric scattering matrix, nevertheless all of which are based on the narrow-band hypothesis and ignore the polarimetric dispersion (PD) effect caused by FR for its high disturbance within the bandwidth. The existent model is no longer well applicable to the future P-band ultra-wideband system with benefits of the high-resolution detection of the subsurface or obscured targets. A novel analytical model of PD based on the frequency-domain range pulse compression is proposed and analysed in this Letter, and the simulation results indicate the spaceborne P-band ultra-wideband SAR system is seriously influenced by the PD effect.