Low‐RCS High‐Gain Broadband Substrate‐Integrated Waveguide Antenna Based on Elliptical Polarisation Conversion Metasurface

ABSTRACT An elliptical polarisation conversion metasurface (PCM) is proposed for Ka‐band applications, integrated with a high‐gain substrate‐integrated waveguide (SIW) antenna to achieve significant radar cross section (RCS) reduction. The PCM elements, arranged in a chessboard configuration, feature a simple yet efficient design with an elliptical pattern symmetric along the diagonal, enabling effective conversion of linearly polarised waves. The antenna employs a broadband dipole excited through SIW slot coupling. Simulation results demonstrate that the PCM unit achieves a polarisation conversion bandwidth of 80.38% (25.3–59.3 GHz) with a polarisation conversion ratio (PCR) exceeding 90%. When integrated with the dipole antenna, the design exhibits a −10 dB impedance bandwidth of 15.08% (33.7–39.2 GHz) and a maximum realised gain of 9.12 dBi, representing a 1.7 dB gain enhancement at 36 GHz. Moreover, the 16 × 16 PCM array configuration achieves an RCS reduction bandwidth of 77.98% (25.85–58.92 GHz), with RCS reduction values exceeding 9 dB across this bandwidth and an average reduction of 12 dB. The proposed antenna has been fabricated and tested, with measured results showing excellent agreement with simulations in terms of and gain performance.