OFD-LFM signal design and performance analysis for distributed aperture fully coherent radar

The estimation of coherent parameters that comprise time delay differences and phase differences with high accuracy is essential to realize transmitting and receiving coherence for distributed aperture fully coherent (DAFC) radar, and the output signal-to-noise ratio gain (oSNRg) is an important attribute used to measure DAFC radar performance. By combining the design of orthogonal frequency division-linear frequency modulation (OFD-LFM) signals with the peak picking algorithm, the impact of signal parameter settings on the estimation accuracy of coherent parameters and oSNRg are studied, and the signal design requirements to obtain high-precision estimation for coherent parameters and high oSNRg are analyzed in this paper. First, the two signal models for DAFC radar are established in multiple-input multiple-output (MIMO) and fully coherent (FC) modes, respectively. The source of coherent parameter estimation error and the impacts of carrier frequency distance on the estimation accuracy of phase differences are then deeply analyzed. Finally, under a condition of reasonable carrier frequency distance, the optimal carrier frequency value is given to achieve the best estimation accuracy of phase differences and the highest oSNRg. The results of simulation and theoretical calculation show that the estimation accuracy of transmitted OFD-LFM signals designed with coherent parameters and oSNRg by peak picking is close to that accomplished by peak picking with the transmission of ideal orthogonal signals.