Low Sidelobe Design for Small-Scale Sparse Array Antennas Using Mechanical Rotation

Reducing the number of antenna elements within a fixed aperture while maintaining low sidelobe levels is a key challenge in sparse array design. Although various sidelobe suppression techniques exist, most are tailored for large-scale arrays and are not directly applicable to small-scale sparse arrays. This paper addresses a critical gap in array design for small sparse arrays with low sidelobes using mechanical rotation and time-averaging techniques. By continuously rotating the array and time-averaging radiation patterns, the mainlobe remains coherent and stable, while the rapidly varying sidelobes are effectively averaged out and suppressed. An analytical model is developed to determine the required integration time, optimize element placement, mitigate Doppler effects, and enhance time-selective radiation pattern strategies. Experimental validation using a four-element circularly polarized array with 0.74λ spacing demonstrates a PSLL reduction of 11.5 dB compared to a conventional non-rotated array, and can be further reduced by 4.7 dB through time-selected pattern optimization. The proposed method has many potential applications, such as passive remote sensing using rotating UAV swarm arrays, making it a flexible and low-cost solution for precision agriculture and environmental monitoring applications.