A smart repeater for weapon location radars based on time-frequency analysis

The smart repeater is a transportable test set for the weapon location radar to evaluate its artillery-locating capabilities without having to use live artillery fire. It retransmits a radio frequency echo that represents the radar return from a shell following the simulated ballistic trajectory when it is triggered by the radar beam. In order to synthesize the echo accurately, we propose time-frequency analysis method combined with pseudo pulse compression to estimate the pulse parameters of the subject radar. Time-frequency distribution is the optimal analysis technique for a linear frequency modulation signal since it will concentrate the signal energy along its instantaneous frequency, while dispersing noise among many frequencies. Therefore we integrate time-frequency analysis with pseudo pulse compression to estimate the parameters of radar pulse such as centroid frequency, frequency modulation rate, amplitude and phase. For the sake of improving the estimation accuracy in the presence of noise and radar electromagnetic environment, both blind deconvolution and power detecting approaches are used. We preprocess the signal by blind deconvolution to extract the raw radar signal from the convolution between the raw signal and electromagnetic environment. The power detecting technique is applied to extract the peak ridge of time-frequency transformation of the signal from interference terms between the signal and noise. After the estimation, a novel method is presented which use digital modulation technique to synthesize the radar echo by inserting the proper delay, Doppler frequency and radar cross-section effects according to the locality and velocity of the simulated shell. Processing steps of the estimating and synthesizing are given in detail. Simulation results validate the effectiveness of these approaches. Development of this smart repeater has been completed and it can provide a quick, thorough performance check of the weapon location radars and minimize the need for expensive.