Wang Xiqin

New image enhancement algorithm for night vision

In order to improve the clearness of images captured at night, a new enhancement algorithm is proposed in this paper. Its characters are: (1) enhancing the dark image with contrast enhancement and histogram equalization in series, so both the local and global information can be used; (2) a contrast transforming function which is suited to deal with dark image is proposed; (3) it can be realized in real time. The new method shows good performance in dealing with night vision images.

Suppressing autocorrelation sidelobes of LFM pulse trains with genetic algorithm

Modulations and diversities, including the Costas-ordered stepped-frequency and nonlinear stepped-frequency waveforms are widely used in linear frequency modulation (LFM) pulse trains to reduce the relatively high autocorrelation function (ACF) sidelobes. An efficient method was developed to optimize the interpulse frequency modulation to remove most of the ACF sidelobes about the mainlobe peak, with only a small increase in the mainlobe width. The genetic algorithm is used to solve the nonlinear optimization problem to find the interpulse frequency modulation sequence. The effects on the ACF sidelobes suppression and mainlobe widening are studied. The results show that the new design is superior to the corresponding stepped-frequency LFM signal and weighted stepped-frequency LFM signal in the terms of the ACF sidelobes reduction and mainlobe spread.

Airborne adaptive MTI scheme with preventing the whitening of the target

A new airborne MTI scheme that applies to non-homogeneous clutter environment is presented. Results of simulation have proved that the scheme has a superior ground clutter suppression performance and can effectively prevent the whitening of a target.

A novel method for evaluating robustness of CFAR radar detectors

A method for evaluating the robustness of constant false alarm rate (CFAR) detectors is presented, which is based on the powerful methodology of influence function (IF) developed in the literature on robust statistics. It can evaluate and compare the robustness of different kinds of CFAR detectors by calculating the first derivative of false alarm probability (FAP) at an underlying distribution, which is named FAP-IF. The FAP-IF of cell averaging (CA) and ordered statistics (OS) CFAR detectors are presented. The computational simulation of radar detection in exponential clutter is also presented to prove the theoretical result.

New CFAR processor independent of original noise distribution

Based on the fact that the result of noncoherent integration of the amplitudes of independent samples of noise is approximately identical to nonzero-mean Gaussian distribution, a Gaussian biparametric constant false alarm rate (GB-CFAR) processor is presented, which is a novel CFAR detector independent of original clutter plus noise distribution. Then the conclusion is presented that its detection performance relates only to the false alarm rate, the number of integration and the mean-to-standard-deviation ratio of original noise. Eliminating the mean of integrated noise amplitude during the detection process is equivalent to taking out partial noise energy, therefore, the detection performance of the GB-CFAR processor exceeds that of the traditional CA-CFAR (cell-averaging CFAR) processor.

Algorithm and new structure for radar sliding MTD

Moving target detection (MTD) is a high-performance signal processing approach for pulse Doppler radar. High-performance radar calls for sliding MTD (SMTD). Traditional SMTD processing massively increases computational load, resulting in difficulty of implementation. A modified moving DFT algorithm and a new SMTD structure are proposed in this paper. The new SMTD structure adopts both batch-mode signal channel estimation and the modified moving DFT algorithm, which leads to a dramatic reduction of the computational load. The new SMTD structure can be regarded as an adaptive filter for other applications as well.

Next generation high speed real-time radar signal processing system

In this paper, the leading characters, parallelism, programmability, scalability and reconfigurability of next generation high speed real-time radar signal processing systems are discussed in detail. An experimental system underway is introduced.

Next generation radar signal processing system

In this paper, the leading characters, parallelism, programmability, scalability and reconfigurability of next generation high speed real-time radar signal processing systems are discussed in detail. Important design issues are studied. An experimental system underway is introduced.

Application of conjugate gradient algorithm to adaptive beamforming

In this paper, the relationship of subarray size, snapshot number and interference number is studied for different gradient computing methods. New forward and backward CGM (FBCGM) and multilayer FBCGM (MFBCGM) methods are proposed. Their advantages are summarized as follows: (1) they can be applied with a small number of snapshots. (2) They can be applied with a weaker constraint for the number of the array elements than that Mandyam (1997). (3) They perform well in coherent receiving environments. (4) They have less computational load compared to SMI and the subspace projection method.

An algorithm based on elevation geometric mean for monopulse radars to track a target at low altitude

Conventional tracking radars are often embarrassed when targets being tracked are flying at low altitude over a flat surface. The basic idea for conventional low-angle tracking techniques is to avert the multipath interference by shielding the antenna from the surface reflection or by eliminating the reflection component from the received signal. This is the most direct way to deal with the well-known multipath effect. A new algorithm using a different idea is presented, with which the signal from the reflecting surface can be used to enhance that directly from the target, resulting in extended accuracy, applicability and efficiency. The estimation of the target elevation angle is expressed as the geometric mean of the target and its images angles relative to the boresight axis. Implementation of the algorithm is quite simple.