Parameter estimation and coherence performance of distributed aperture coherent radar based on phase synchronization

For distributed aperture coherent radar with a general architecture, a signal model for coherent parameter estimation and coherent processing based on system phase synchronization is proposed in this paper, and the sensitivity of parameter estimation and coherent processing performance to synchronization errors is analyzed in detail. A closed-form hybrid Cramer-Rao bound (HCRB) of the estimation of time delay difference is first derived in multiple-input and multiple output (MIMO) work mode. Following this, in fully coherent work mode, the analytical formula of output signal-to-noise ratio gain (oSNRg) is addressed, and a numerical solution of the analytical formula is obtained by using high-order polynomial fitting. The principle of antenna configuration is then studied. It is concluded that the estimation accuracy of time delay difference or coherent processing performance is determined by both synchronization error and input SNR. Compared with existing methods, the method based on phase synchronization can yield higher estimation accuracy of time delay differences and better coherent processing performance, given the assumption that the phase synchronization error is small and the input SNR is low.