Direction-Finding Based on Time-Modulated Array Without Sampling Synchronization

A two-element direction-finding method based on a time-modulated array (TMA) without sampling synchronization that exploits new asymmetric time sequences is proposed. The necessity of synchronization between the radio frequency (RF) switches, and analog-to-digital converter (ADC) for the existing direction-finding methods based on a TMA, and the influences of synchronization errors on the phases of different harmonics are first analyzed, and modeled. By considering asymmetric time sequences, and the mathematical relationship between adjacent harmonics, the proposed method can estimate the direction of arrival without synchronization. Compared to the existing methods, the proposed method avoids the synchronization between the ADC, and RF switches while keeps the similar accuracy performance. Numerical simulations are provided to show the feasibility, and effectiveness of the proposed method. A simple S-band two-element TMA is fabricated to show the synchronization problem, and verify the direction-finding method.