An Integrated Scattering Cancellation and Modification Approach for Broadband RCS Reduction of Array Antenna

This paper presents a design method of integrating scattering cancellation with array-level modification techniques for broadband RCS reduction (RCSR) of an array antenna. Taking a circular patch element as an example to explain how the RCSR method is used, an L-shaped feeding structure is adopted, with a dielectric substrate of Arlon Diclad 880 (tm). First, two elements with equal scattering amplitude but opposite-phase characteristics are proposed by adjusting the radiation patch dimensions and loading slots on the small patch based on characteristic mode analysis (CMA). Through arrangement of these two elements in a 2 × 2 array configuration, effective RCSR is demonstrated across 3.5–9.5 GHz. To further broaden the RCSR bandwidth, the 2 × 2 array is modified again on the ground plane using CMA. Through the integration of scattering cancellation and array-level modification techniques, a broadband RCSR design of the array antenna is realized across 2.5–11 GHz. To demonstrate the universality of the design method, 2 × 2 and 4 × 4 array antennas are designed, fabricated, and tested. The 2 × 2 array antenna can realize an average RCSR of 10.3 dB and a peak RCSR of 22 dB across 2.5–11 GHz. The 4 × 4 array antenna can realize an average RCSR of 8 dB and a peak RCSR of 23 dB across 2.5–10.5 GHz. Meanwhile, the transmission and radiation performance remains basically unchanged. The 2 × 2 array antenna works from 3.76 GHz to 5.45 GHz (36.7%) and the 4 × 4 array antenna works from 3.80 GHz to 5.30 GHz (31.1%). Their gains are 9.9 dBi for the 2 × 2 array antenna and 15.9 dBi for the 4 × 4 array antenna at 4.5 GHz. Measured results show a good agreement with calculated ones, which verifies the effectiveness and correctness of the design method.