A Broadened Beamwidth and Cosecant‐Squared Pattern Antenna Based on SIW Slot Array for Wide‐Range and High‐Precision Radar Detection

ABSTRACT To meet the requirements of wide‐range and high‐precision radar detection, a beamformed substrate integrated waveguide (SIW) slot array antenna is presented and investigated. The proposed antenna achieves a broadened beamwidth pattern with low sidelobe levels (SLLs) while maintaining a required gain level in H‐plane and simultaneously realizes a cosecant‐squared beam pattern in E‐plane for high‐precision detection. The antenna comprises 32 series‐fed standing wave slot arrays, each containing 12 slot elements. To achieve wide beam coverage under a prescribed gain constraint, a genetic algorithm (GA) is introduced to synthesize the special radiation patterns. The optimization process employs amplitude weighting of the series‐fed units to achieve a broadened beam by shifting the first null outside the target range in H‐plane, while amplitude and phase weighting are applied to realize a cosecant‐squared radiation pattern covering 0° to 30° in E‐plane. A 32 × 12 SIW slot array antenna operating in the 9.2–9.6 GHz band is designed and fabricated. Measurement results demonstrate an H‐plane pattern free of nulls within ±16° with low SLLs below −28.1 dB, and a cosecant‐squared beam from 0° to 30° in the E‐plane with SLLs suppressed to‐ 20 dB. The achieved performance indicates that the overall methodology is well‐suited for such slot antenna arrays.