Direction Finding by Time-Modulated Linear Array

The direction finding method by the time-modulated linear array (TMLA) is analyzed and verified. The direction of arrival (DOA) can be calculated out by analyzing the spectrum characteristic of the received signal after the time modulation. Its principle is as follows. Because of the periodic modulation, the fundamental and harmonic components are generated in each element simultaneously. After the combiner, the harmonic components' characteristic of the combined signal is influenced by the DOA. Through analyzing their mathematical relationship, the DOA can be calculated out directly. Compared with the existing direction finding methods, the proposed method has two main advantages. One is that only a single RF channel is used, and the other is that its precision can be improved by the time accumulation. The main calculation amount of the proposed method locates in the spectrum estimation for the received signal and the matrix inversion for the harmonic characteristic matrix. Numerical simulations are provided to verify the proposed method, and the related factors influencing on the direction finding precision are analyzed. A simple S-band eight-element TMLA is constructed and tested to verify its effectiveness. Finally, some conclusions are drawn, and the further research is sketched out.