The Effect of Coherent Frequency Diverse Array on Watson-Watt Direction-Finding System

Frequency diverse array(FDA) offer potential applications for enhancing the RF safety performance of FDA systems. This is due to the time-varying angle-distance coupling characteristics of the transmit beam map, which are caused by small frequency shifts between subarray elements. In this paper, we investigate the impact of coherent FDA signals on amplitude-based direction-finding systems, taking the Watson-Watt direction-finding system as an example. Firstly, we establish receiving model for direction finding of FDA signals. Secondly, we evaluate the error of the direction-finding system when using coherent FDA signals and analyze it with the Cramér-Rao lower bound(CRLB). Finally, we conduct a simulation analysis to validate the proposed theory. Both the theoretical analysis and simulation results demonstrate that coherent FDA signals can improve the radio frequency(RF) stealth performance. Specifically, the analysis and simulation results reveal that coherent FDA signals exhibit superior low-intercept performance for the Watson-Watt direction-finding system. These findings can be applied to all amplitude direction-finding systems.