Size-Limited Q-Band Circular Switched Parasitic Array Antenna With Small Elevation Beamwidth

A novel circular switched parasitic array (CSPA) antenna operating in the Q-band and capable of electronically switching its main beam over a large field of view of 360° in the horizontal plane is presented. The core component facilitating the beam switching consists of a circular parallel plate waveguide (PPW) section containing a printed circuit board with a central parallel plate mode (PPM) launcher surrounded by 12 electronically switchable PPM reflectors with increased bandwidth. The circular PPW section is flared into a radial waveguide whose diameter is reduced by shaping a foam filling material, originally incorporated for mechanical stability reasons, into a circumferential elliptical lens. By doing so, a small elevation half-power beamwidth is achieved with a size-limited geometry. A tube-like radome protects the circumferential aperture and further increases mechanical stability. Details on antenna design, manufacturing, and measurement results are given, successfully demonstrating the functionality of the concept. The antenna represents a step toward a cost-effective solution for future small-cell mobile networks millimeter-wave wireless backhauls.