Direction-of-arrival Estimation using Compressive Frequency-difference Beamforming

Frequency-difference beamforming offers an alternative method for estimating direction-of-arrival (DOA) with a sparse receiving array. However, it suffers from reduced spatial resolution due to forming the beam at a low frequency, known as the difference frequency. Consequently, this unconventional beamforming approach can hinder the discrimination of closely spaced targets. This study proposes a simple yet effective method to enhance the spatial resolution of frequency-difference beamforming. Drawing inspiration from the compressive sensing employed in conventional beamforming, we introduce a sparsity-promoting constraint in the formulation of frequency differences. This enhancement, termed compressive frequency-difference beamforming, enables sharp estimation of the spatial DOA spectrum. Under conditions where the signal-to-noise ratio remains sufficiently high, the proposed method exhibits superior separation performance compared to traditional frequency-difference beamforming. Experimental validation using real sea data supports the validity of our approach.