Single-Channel Spatial Spectrum Estimation Direction Finding by the Time-Modulated Linear Array

In this letter, a novel direction-finding method with spatial spectrum estimation is proposed and verified, based on the time-modulated linear array (TMLA) and a single radio-frequency channel. Its principle is as follows. The TMLA receives and periodically modulates the incident signal. After the power combiner, the modulated signal is down-converted to the intermediate frequency and sampled in the single-channel receiver. In the digital domain, the array manifold vector can be calculated from the Fourier coefficients and the harmonic characteristic matrix related to modulation sequences, and thus, the autocorrelation matrix can be estimated. Afterward, the multiple signal classification algorithm is applied to estimate the incident angle, and the spatial smoothing method is exploited to deal with the direction finding of coherent sources. The proposed method has a simple structure and low computational complexity. Numeric simulations and corresponding experiments have been conducted to verify its effectiveness.