Broad-Angle and Low-Scattering Microstrip Antenna Design Using Characteristic Mode Analysis

In this paper, the scattering-field formula for arbitrary angle incident plane wave is given based on characteristic mode theory. According to the formula, the modal amplitude is used as a criterion to choose significant scattering modes and a broad-angle low-scattering antenna design method is proposed. With the design method, a broad-angle low-scattering aperture-coupled microstrip antenna is designed, fabricated, and tested. Three slots are placed at the radiation patch and two pairs of slots are placed at the ground, so as to suppress the important scattering modes while keeping the radiation modes work properly. Compared to the reference antenna, the proposed antenna achieves at least 6 dB average RCS reduction (RCSR) and minimum peak RCSR of 17 dB over the broad angle of −90° to 90° from 4 to 5 GHz. Meanwhile, its transmission and radiation performance keep well from 2.81 to 2.98 GHz (5.9%) and its gain is 6.1 dBi at 2.9 GHz. The measured and simulated results are in good agreement, which validates the design method.