Estimation of Insect Wingbeat Frequency Based on Micro-Motion Phase Autocorrelation and Micro-Doppler Power Concentration

Wingbeat frequency (WBF) is a key parameter for identifying airborne migratory insect species. Radar is one of the most effective tools for measuring the WBF, reliably operating day or night, and under various weather conditions. However, the scattering signal from the insect body is extremely weak, and the wingbeat echo intensity is an order of magnitude smaller than that of the insect body. This results in low signal-to-noise (SNR) wingbeat echoes, making WBF extraction challenging. Traditional amplitude methods achieve acceptable WBF extraction success rates under high SNR conditions, but exhibit significantly lower success rates when SNR drops. Subsequent studies have shown that WBF can be extracted by exploiting the micro-Doppler modulation of the echo phase induced by wing beat. However, performance degradation occurs in phase-based methods because airflow disturbances or maneuvering by the insect in flight introduce higher-order nonlinear phase fluctuations that intermix with wingbeat micro-Doppler phase components. To fully use both amplitude and phase information for improved WBF extraction under low SNR conditions, this article proposes a novel method for estimating insect WBF based on micro-motion phase autocorrelation and micro-Doppler power concentration. First, an adaptive filtering approach using micro-motion phase autocorrelation matching is proposed. It can effectively mitigate nonlinear Doppler interference. Secondly, the long-duration micro-Doppler power concentration method based on micro-motion paths and phase model matching is proposed. It greatly improves the performance of the WBF estimation method under low SNR. Validated through simulations and field radar data, the proposed method effectively extracts the WBF of naturally migrating insects. In a field test using echo signals from locusts, the WBF detection success rate of the proposed method was 22% higher than that of the traditional method.