Design of a 132 GHz 1×4 RHCP Microstrip Antenna Array with Rotman Lens for Inter-Satellite Links

This paper presents a 1×4 microstrip antenna array designed for inter-satellite communication at 132 GHz, featuring right-hand circular polarization (RHCP) and Rotman-lens-based passive beam steering. The slot- and stub-loaded circular patch element achieves a 27% impedance bandwidth (118.4-154.1 GHz), a 5.6 % axial-ratio bandwidth (128.8-136.3 GHz), a peak gain of 6.78 dB, and 96.6 % simulated radiation efficiency. A five-port Rotman lens provides ±30° beam steering, while the inter-element spacing (0.594λ) and scan-angle-dependent tapering coefficients are optimized to suppress sidelobes and preserve polarization purity. Full-wave simulations confirm sidelobe levels between -5.5 dB and -13.6 dB and an axial ratio below 3 dB across the 130-134 GHz inter-satellite-link (ISL) band, with a realized array gain of 9-10 dB.