A Millimeter Wave Broadband and High Isolation Coupler Based on Ni‐Spoof Surface Plasmon Polariton (SSPP) Matched Load

ABSTRACT This letter proposes a broadband millimeter‐wave rat‐race coupler featuring a simple structure, ease of integration, and high isolation, achieved by innovatively incorporating a nickel‐based SSPP matching load at the isolation port. The coupler is further integrated with a microstrip‐to‐grounded coplanar waveguide (GCPW) transition and a waveguide antenna for performance validation. The coupler can be fabricated using standard printed circuit board (PCB) fabrication processes, while the waveguide antenna is manufactured through precision mechanical machining techniques. Simulation and measurement results show that the rat‐race coupler achieves excellent return loss and high isolation (greater than 30 dB) in the frequency range of 76–81 GHz.