A Compact Maritime Harmonic Radar Antenna for Navigation and Search-and-Rescue

This paper presents a compact dual-band dual-polarized slotted waveguide array antenna designed for a maritime harmonic search-and-rescue system. The harmonic radar transmits signals in the S-band and receives clutter-free signals in the C-band through transponders integrated into life jackets. To realize a compact solution, S-band and C-band subarrays are integrated into a shared housing. The S-band utilizes inclined slots etched on the narrow wall of a rectangular waveguide to provide horizontal polarization, while the C-band employs longitudinal slots cut into the broad wall of a rectangular waveguide for vertical polarization. To obtain a directive beam in the elevation plane, a printed tapered Yagi-Uda-type director array is used for the S-band SWA, while a tapered dielectric slab waveguide is employed for the C-band SWA to avoid degradation and beam tilting of the radiation patterns caused by the proximity of the S- and C-band array antennas. The fabricated antenna (4000mm × 650mm × 170mm) achieves high gain, narrow half-power beamwidth of 1.9°, and sidelobe levels below −30 dB in the azimuth plane. In the elevation plane, a 26° half-power beamwidth with sidelobe levels below −20 dB is obtained. Simulated and measured results are in good agreement, confirming the proposed design.