Multi-Beam Conformal Leaky-Wave Antenna Fed by an Integrated Quasi-Optical System

This paper presents a fully conformal antenna system composed of an integrated multi-layer quasi-optical system and a conformal leaky-wave antenna (CLWA). The conformal system enables simultaneous beam steering in the E- and H-principal planes, multi-beam capability, and mitigation of geometric defocusing. The work represents a novel integration of quasi-optical structures with CLWAs. The CLWA is constructed from an array of slots on a double-grounded substrate illuminated by the conformal quasi-optical system. The antenna system operates in the band of 22 GHz to 26 GHz with a design frequency of 24.15 GHz. The radiation patterns in the E- and H-planes of the CLWA are controlled by the leaky-wave mode and the quasi-optical system, respectively. The quasi-optical system is illuminated by seven input ports enabling azimuthal beam switching. The spacing between consecutive slot elements of the CLWA has been engineered to compensate for the defocusing induced by the conformal shape, such that the central feed horn in the focus of the quasi-optical system radiates broadside at 24.15 GHz. Numerical results are validated by a prototype in printed circuit board (PCB) technology. The input ports feature a reflection coefficient ≤ −10 dB in the band of 19.75 GHz to 25.50 GHz, corresponding to a fractional bandwidth of 25.41%. The measured gain for the broadside beam is 23.35 dBi at 24.15 GHz with a radiation efficiency of 65.36%. The antenna can cover an angular range of approximately 33° in elevation via frequency steering and a maximum of ±36.5° in azimuth via beam switching.