Low-Sidelobe Antenna Array Based on Evanescent Mode of Cutoff Waveguide

Low-sidelobe antenna arrays are widely used in the wireless systems for the anti-interference receiving. To achieve low sidelobe, the amplitudes of each array element follow a tapered distribution, which is provided by properly designed feeding networks. In this article, as a different feeding approach for low-sidelobe antenna array, the evanescent mode of a cutoff waveguide is engineered to generate a symmetric and exponential-decay distribution for array elements. To verify this strategy, an array of slots is transversely etched with equal spacing on a
$4.67\lambda _{0}$
-length cutoff waveguide operating at its evanescent mode, achieving a sidelobe level (SLL) lower than −18.8 dB with a gain of 13.7 dBi through measurement, agreeing well with the simulations. Moreover, by optimizing the element spacing on the same cutoff waveguide, the antenna array achieves an extremely low SLL of −24.1 dB and a gain of 13.1 dBi. The proposed evanescent-mode waveguide enables low-sidelobe antenna arrays with the merits of simple structure, compact dimensions, and high aperture efficiency for potential applications in radar and communication systems.