The closed-form CRB (cramer-rao bounds) of the coherent parameters estimation, which include time delay differences and total phase differences, are derived for the distributed aperture coherent radar with general architecture firstly. Then under the assumption that time delay and phase synchronization errors are all existing, the performance bound of oSNRg (output signal-to-noise ratio gain) is developed based on the aforementioned CRB (Cramer-rao bounds). It is concluded that: the CRB of total phase differences is independent on the carrier frequency and effective bandwidth. More transmitters give higher oSNRg. However, as the number of receivers increase, the oSNRg gradually improve with the input SNR being high sufficiently, and worsen with the input SNR being low. Finally, the numerical examples dem-onstrate the validity of the theoretical results.%针对一般结构的分布式全相参雷达，首先推导了包括时延差及“和相位差”的相干参数估计的克拉美—罗界（CRB）闭式解；然后考虑时延和相位补偿误差同时存在时，分析了全相参模式下的输出信噪比增益（oSNRg），基于相干参数估计的CRB，给出了oSNRg的上界的数值解。结论表明，“和相位差”的CRB与信号载频及有效带宽均无关；oSNRg随着发射天线数的增加而提高；而增加接收天线数，能否提高oSNRg取决于输入信噪比大小，较大时则oSNRg随之提高，较小时反而随之下降。最后仿真实验验证了研究结论的正确性。
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