Sidelobe Level Reduction for a W-Band SIW Slot Array Antenna by only Reversing Offset Direction of Partial Slots

For a traditional slot array antenna, the sidelobe level (SLL) is usually reduced by applying taper amplitude distribution. Typically, each slot of the linear array and each stage of the power divider should be carefully modulated to satisfy the requirements on the amplitude of the low SLL in both E-and H-planes. However, for a slot array at W-band or higher, the varied slot distribution and the unequal feeding network are very sensitive even to the slightest inaccuracy of each parameter, which makes it very challenging to distinguish the expected amplitudes within the constraints of fabrication resolution. Meanwhile, it will take a very long iteration optimization time and the SLL performance is sensitive to the frequency, i.e., the operating bandwidth is very narrow. In this communication, a simple and effective method, by only reversing the offset direction of partial slots, to reduce the SLL in two planes for a W-band substrate integrated waveguide (SIW) slot array antenna with expanded bandwidth is proposed. For the SIW slot array, 0°/180° radiation phase can be easily achieved by placing adjacent slots on the opposite and same side without changing the length and offset of the slots. This feature is applied to optimize the SLL of the SIW slot array in two planes with the improved greedy algorithm. In this case, delicate and susceptible varying slot distribution and unequal power dividers are substituted by simply reversing a portion of radiating slots. Finally, a 16×16 low SLL SIW slot array antenna prototype with extended bandwidth is designed. The measured results exhibit a-19.1 dB low SLL at 94 GHz. The presented lightweight, low-loss, and high-integration W-band SIW slot array with low SLL provides good promise in the unmanned aerial vehicles (UAVs) SAR imaging application. © 2023 IEEE.