Study On The Detection Theorem Of The Skywave MIMO-OTH Radar

Due to the large detection distance, wide surveillance area, high detectionprobability to stealth aircraft, and other advantages, the skywave over the horizon （OTH）radar is of great significance in the war. This dissertation considers the employment ofmultiple-input multiple-output （MIMO） radar technique in the skywave OTH radar,namely the skywave MIMO-OTH radar, and studies its detection performance. Theinfluence of the multipath propagation and the radar system parameters on the detectionperformance of the skywave MIMO-OTH radar is analyzed.Based on the propagation feature of the skywave OTH radar signals over theionosphere, the received signal mode is derived, which is capable to describe theinfluence of the ionosphere phase perturbation and the multipath propagation oftenencountered in skywave OTH radar. According to the signal model, we deduce thecorrelation of the received signals from different transmitting antennas, receivingantennas and propagating paths, and provide the theoretical formula to determinewhether the received signals are correlated or not. It is also proved that the receivedsignals are more likely to be uncorrelated by increasing the interval between differenttransmitting/receiving antennas or the difference between the frequencies of thetransmitting signals.Considering the additive complex white Gaussian noise, the optimal detector isderived under Neyman-Pearson detection criterion. The dissertation analyzes thedetection performance of the radar system under NP detector and derives thecorresponding diversity gain. Assume the skywave MIMO-OTH radar is composed ofM transmitting antennas and N receiving antennas. If there areLm differentbackward propagation paths （the signal propagates from the target to the receivingantenna） with respect to the m th transmitted signal, we prove that the diversity gain ofthe radar system satisfiesg g≤Σ_m=1^M min{N, L^m}. Under certain conditions, increasing thenumber of the transmitting antennas, the number of the receiving antennas, or thenumber of the backward propagation paths can increase the radar diversity gain,improving the radar detection performance. It is also proved that the skywave MIMO-OTH radar has better detection performance than the traditional skywave OTHradar.At last, the miss detection probability of the skywave MIMO-OTH radar and theskywave OTH radar under different scenarios are derived through numericalsimulations. The influence of the radar system parameters and the multipath propagationon the radar diversity gain is analyzed and the theoretical analysis is proved to becorrect by analyzing the simulation results.