The Structure and Performance Study of Single-Loop Spiral Differential Microphone Array

This paper investigates a single-loop spiral differential microphone array, engineered based on the Jacobi-Anger expansion. The circular differential microphone array it employs is capable of generating a frequency-invariant beampattern that can be steered in any direction. However, this array faces performance deterioration due to the zero value of the Bessel function at specific frequencies, leading to nulls in white noise gain and directivity factor. The concentric circular microphone array, while addressing these nulls, requires a larger number of microphones and a more extensive array distribution area. We propose a single-loop spiral differential microphone array, structured on the Archimedes spiral. The study compares and analyzes differences in white noise gain, directivity factor, and beam pattern between the proposed array and the conventional circular differential array. The impact of spiral parameters on the array’s performance is also examined. Simulation results demonstrate that the single-loop spiral differential array mitigates the issues of deep nulls in white noise gain and directivity factor at certain frequencies, observed in the circular differential array. This is achieved without increasing the microphone count, showcasing superior performance. Furthermore, as the number of microphones increases, the array’s beamforming performance is progressively enhanced.