Research On Some Key Techniques In Radar Signal Processing

Because range ambiguity exists on weather radar, two methods are offered to solve this problem. The primary surveillance radar faces all kinds of jamming, so the function of jamming spectrum analysis and transmitting frequency selection is facilitated. Different kinds of methods are used to simulate the encoding and decoding process of the mode S second surveillance radar, the bit and confidence declaration algorithm is improved. What the paper has done and the innovation points are listed as follows:1) An improved batch mode method that can mitigate range ambiguity is put forward. In order to cut down the ambiguous area, noise power threshold parameter is set. When it comes that both of the first time echo power and the second time echo power are less than the noise power threshold, there is no need to apply the ambiguity resolving algorithm, thus more information is retained from the echo data. The special time scheduling and instruction analysis are designed, and both EPLD and DSP are programmed to facilitate the ambiguity mitigating algorithm. The improved algorithm is applied on a weather radar, data are collected which shows that this method has a good effect of mitigating range ambiguity.2) For mode S second surveillance radar, a bit and confidence declaration algorithm is brought forward, and the baseline multi-sample algorithm is improved. The first step, the moving average method is used to process the sampled data; the second step, two statistical variables are added to avoid false declaration. The simulation under Matlab environment proves the correctness of the improved algorithm. During encoding process two methods which are named long division and look-up table are designed with VHDL and simulated also, after that these two methods are compared. The hardware design chart of the encoding and decoding system of the mode S second surveillance radar is given.3) A new signal processor based on TigerSHARC DSP is designed and the computing ability is increased a lot. The data processing flow is optimized, and the data are divided into two parts and are feed into two DSP chips to facilitate parallel computing, thus saves the processing time. The characteristic of the SZ (8/64) phase coding is validated, simulated data are used to emulate the function of mitigating range ambiguity, and this kind of coding is also compared with the n/4 phase coding. The signal processor has a broad application area and the phase coding function can also be facilitated on it, now the processor has applied on many radars.4) A kind of frequency agility mehod which can adaptively select frequencies of the primary surveillance radar is presented. During the interregna of the longest transmitting period all the working frequencies are sampled and averaged to get the amplitudes of these frequencies. Then the amplitudes are analyzed and judged. After that the optimized frequencies are offered under the fixed frequency mode and frequency diversity mode respectively. All the above functions are realized with FPGA. The communication application is programmed under the VxWorks operation system to send the amplitudes of the frequencies to the monitor and control system. This module has applied on a primary surveillance radar, and it improved the anti-jamming performance of the radar.