Difference-Frequency MUSIC for DOAs

The direction-of-arrivals (DOAs) of plane waves in a high-frequency region are estimated without spatial aliasing using multi-frequency processing. The method exploits the difference frequency (DF), the difference between two high frequencies. This enables processing data in a feasible region without spatial aliasing. We analyze DOA characteristics upon DF processing and propose a MUSIC-based method dealing with multi-DF and multi-snapshot. Multiple DFs having the same frequency difference allow processing multi-DF equivalently to multi-snapshot. We propose a method that considers all DFs and snapshots jointly and a joint DF method providing a single snapshot DF-MUSIC that does not require stationary DOAs. Numerical examples validate the effectiveness of the proposed method and its DOA performance is discussed.