A Multibeam Cylindrically Conformal Slot Array Antenna Based on a Modified Rotman Lens

A dual-layer multibeam conformal slot array antenna operating at a center frequency of 10 GHz is proposed in this paper. The antenna consists of a microstrip Rotman lens and a substrate-integrated waveguide (SIW) array of
$10{\times} 10$
radiating slots, which is axially mounted onto a cylindrical surface with a radius of 90 mm, i.e.,
$3\lambda _{0}$
. The Rotman lens feeds the slot array through the coupling slots in the broad sides of the SIWs. An improved design process is introduced for realizing a conformal Rotman lens for cylindrically conformal arrays. There are unique requirements for the phase distribution and phase compensation in cylindrically conformal applications. The Rotman lens and slot antenna are built and optimized in full-wave simulation software. To validate the proposed concepts, a conformal antenna prototype is implemented and measured. The experimental results demonstrate a scanning range of ±46°, with a −3 dB crossover level between adjacent radiation beams in the E-plane and a −20 dB sidelobe level in the H-plane. The measured and simulated radiation patterns of all the scanned beams are in good agreement. This type of multibeam conformal slot array has been theoretically and experimentally studied, and it demonstrated the potential for applications in aircraft, missiles, and high-speed vehicles.