Meng Xiande

Scheme of adaptive polarization filtering based on Kalman model

Abstract A new kind of adaptive polarization filtering algorithm in order to suppress the angle cheating interference for the active guidance radar is presented. The polarization characteristic of the interference is dynamically tracked by using Kalman estimator under variable environments with time. The polarization filter parameters are designed according to the polarization characteristic of the interference, and the polarization filtering is finished in the target cell. The system scheme of adaptive polarization filter is studied and the tracking performance of polarization filter and improvement of angle measurement precision are simulated. The research results demonstrate this technology can effectively suppress the angle cheating interference in guidance radar and is feasible in engineering.

Angle glint suppression for millimeter-wave radar based on polarization filtering

For the millimeter wave radar, angle glint of extended targets is the main angle error. A new kind of dual polarization wide band millimeter wave radar is proposed and a glint suppression technology based on polarization filtering is studied in this paper. Firstly the echo-signal is processed into one dimension range profile based on high range resolution of millimeter wave radar and the effective strong scattering centers are detected, secondly the polarization filtering is used to the signals in the range cell where the scattering centers exist in order to suppress clutter and increase the angle measurement precision of single scattering center, finally the angle of each scattering center is measured by amplitude sum/difference and the target average angle is obtained by weighting all the scattering centers, which can realize the correct track on the target. Theoretical analysis and simulation results indicate that the technology can obviously increase the angle measurement precision of the whole target.

The system compensation of isar

A method for compensating the amplitude-phase distortion of ISAR system is described. This system compensation can be separated into two parts: the compensation of the system before the mixer and the compensation of the system after the mixer. The, experimental results of the compensation in microwave dark room are given. It is shown that the method presented is effective.

Study on the angle glint suppression technology for high resolution dual polarization radar seeker

For the high resolution dual polarization guidance radar, a new glint suppression technology is proposed in this paper. The technology can notably ameliorate the angle measurement precision and improve the anti-jamming ability of the radar. The basic idea is that the effective scattering centers in radius of the extended target are separated based on the twice detection of amplitude and polarization in order to eliminate the effect of interference scattering centers firstly, then the angles of each effective scattering centers are measured according to mono-pulse method, finally the average geometer position of the target is determined by weighting the measured angles of the effective scattering centers and tracking reliability of the target is realized. The signal model and specific angle glint suppression algorithm are given, and the effectiveness of the algorithm is testified by simulation.

Study on the method of RF filtering for the new polarization radar

The terminal guidance radar is faced with the interferences including the passive chaff and the active off-board decoy. It is effective to adopt polarization signal processing to suppress such interferences. Traditional polarization signal processing is finished in the video frequency, and the radar receiver would be saturated and disabled when the interference is strong enough. For this, a new adaptive polarization agile microwave network is proposed in order to solve the problem in this paper. The microwave network can suppress the interferences in the RF band before the interferences enter into the receiver, so we call it RF polarization filter. The structure and theorem of the RF polarization filter are given and the estimates of the interference polarization parameter arc also discussed.

Measurements for phase characteristics of the SAW device with large bandwidth and long pulse duration

A method for measuring the nonlinear frequency modulation of a LFM (linear frequency modulated) signal generated by a SAW device with large bandwidth and long pulse duration is described. The measured results are processed by computer and their effects on the ISAR (inverse synthetic aperture radar) imaging are discussed.

Research of multi-thresholds detector for finding little targets of maritime ship

Multi-thresholds detector techniques of special targets of maritime ship in complex strong sea clutter and noise are being studied. In the techniques, the properties of sea clutter, spatial. Signals, minimum error detection probability caused by noise interface are considered. The theoretical analysis and computer software are implemented for multi-thresholds detector. The research results have been applied in a radar station. The practical testing results show that the multi-thresholds detector has good performance.<<ETX>>

A new approach to improve the accuracy of the angle measured in multi-target situation for OTH radar

The sum and difference amplitude comparison method of a secondary surveillance radar is conventional in azimuthal direction indication but is effected by much azimuthal errors, especially by the multiple-targets situation. After a discussion of azimuthal estimation techniques and performance, with special reference to the OTH HF radar applications, a novel estimation, which is called MSMWSA (method of symbol maximum and weighted sidelobe averaging), for this radar is described. The proposed technique is a close approximation of the maximum likelihood estimator (MLE) taking into account the receiver characteristics as well as the multiple-targets situation. The performances, obtained by analysis and computer simulation, are compared with those of a traditional estimator.<<ETX>>

Adaptive multi-thresholds detection algorithms for finding little targets of maritime ship

A serious degradation of detection probability(P/sub d/) in a conventional cell-averaging constant alarm rate (CA-CFAR) detector is known to be caused by the presence of interfering targets in the set of reference cells. A new CFAR detection algorithm of multithreshold in which three tentative estimates of the noise level in the test cell are obtained by independently processing output of the leading and the lagging cells is proposed and studied. The performance of multi-threshold CFAR detector is analyzed in both a benign environment and in an environment of an arbitrary number of interferers in the sample set. A Rayleigh fluctuation target mode (Swerling Case I) is used as a model for the received signal. The results have been applied in Radar Station. The practical testing results show that the multi-thresholds detector has good performance.<<ETX>>