A Fixed-Frequency Beam Scanning Circularly Polarized Leaky-Wave Antenna Based on Half-Mode Substrate Integrated Waveguide

This paper presents a novel circularly polarized (CP) leaky-wave antenna utilizing a half-mode substrate integrated waveguide structure for continuous beam scanning at a fixed frequency of 10 GHz. By employing a modified unit cell equipped with two varactors, the antenna enables continuous beam scanning at a predetermined frequency from backward (-30°) to forward (+32°) directions, including broadside (0°). Simulation and experimental results demonstrate good agreement, with | S11| below -10 dB and axial ratio under 3 dB across main beam directions. The prototype antenna achieves a peak gain of 10.4 dBic at broadside and exhibits a gain variation of less than 2.6 dB during beam scanning. Its compact size and stable performance make it suitable for radar systems requiring CP beam scanning at fixed frequencies.