Joint DOA-Distance Estimation Method for Radar Using a Novel Time-Domain Wideband Synthesis System

In this article, a joint direction of arrival (DOA) and distance estimation (JDDE) method using a novel time-domain wideband (WB) synthesis signal system is proposed. In contrast to traditional time-domain synthesis (TDS) methods, which transmit subpulses separately, a uniform linear array (ULA) is used, and all stepped linear frequency-modulated (SLFM) subpulses are transmitted simultaneously. The echo signal is mixed with each transmitted signal of the corresponding antenna and filtered to separate the single-frequency components from different targets and array elements for synthesis. Single-frequency components have different frequencies and discontinuous phases due to wave-way differences. To solve the problem that single-frequency components cannot be synthesized directly, the frequency and phase of single-frequency components need to be calibrated, including frequency conversion and phase shift, which require DOA information of the targets. Consequently, a high-precision DOA algorithm that employs phase difference fitting, along with the corresponding generic phase unwrapping algorithm, is designed for the characteristics of the arrays and signal system in this article. After obtaining the DOA information, the WB synthesis algorithm is applied to synthesize the single-frequency components to obtain high-resolution ranging results. The theoretical analysis and simulation results show that the method has high distance resolution and JDDE accuracy. In a multitarget environment, the number of targets is not limited by the number of antennas. In addition, unlike traditional WB synthesis methods, the method utilizes multiple transmitting antennas to send SLFM signal pulses simultaneously rather than sequentially, which enhances the response speed of the radar.