Study On Target Detection Using CDMA Pilot Signals

The dissertation studies target detection method based on CDMA pilot signals. By using the good passive detection performance of CDMA pilot signals, the characteristic parameters of targets are measured to detect targets.On the basis of introducing basic principles of the bistatic radar system and architecture of CDMA downlink channels, the passive detection performance of CDMA pilot signals is analyzed. Then, a scheme of target detection utilizing CDMA pilot signals is proposed. Specially, the key techniques in this scheme are discussed in details and an experiment of target detection is completed by the scheme.Firstly, the dissertation describes the radar equation of the bistatic radar, which expresses the relationship between operating range and working parameters. The operating range of this radar system is presented by cassini ovals. Secondly, the coding and modulation process of CDMA downlink channels are discussed. Then, the detection performance of the pilot signals is analyzed and results indicate that the pilot signals have good detection performance both in distance and velocity, which can be used for passive detection. Thirdly, a signal processing scheme of target detection using CDMA pilot signals is proposed, which is mainly composed of direct-path signals interference suppression, target echo signals detection and passive location.Aiming at direct-path signals interference suppression, an improved normalized LMS adaptive cancellation is adopted, and simulation is made by accumulating the real data. Simulation results show that the method achieves a good cancellation performance for the pilot signals in receive data. Aiming at target echo signals detection, long-time coherent accumulation processing is adopted. Simulation results show that the method improves the power of target echo signals. Aiming at the target detection and location, velocity measurement and location solution methods are discussed. Finally, an experimental system is constructed based on the detection scheme to detect the position and velocity of cars on the freeway.The experimental results demonstrate that the concept of utilizing CDMA signals for passive detection is feasible, which is in accordance with the good detection performance based on theory.