Multi-beam pillbox antennas in the millimeter-wave range

This work deals with the comparison between various configurations of multi-beam pillbox antennas. The antenna systems present the same pillbox architecture and consist of three parts: feeding part, quasi-optical system, and radiating part. Two different radiating structures and system excitations are considered. A leaky-wave solution and an array of slotted waveguides have been used as radiating parts. In particular, an array of slots etched on the uppermost metal layer of the pillbox structure and 23 waveguides (with 8 radiating slots each) are adopted for the leaky-wave and slotted waveguide solutions, respectively. For the feeding part beam-switching and mechanical scanning mechanisms have been selected. In the first case, seven integrated horns are placed in the focal plane of the integrated parabola to radiate seven beams in the far field, while in the second case (mechanical scanning) one single horn is moved on a straight line in the focal plane of the parabola so as to achieve the beam scanning. The quasi-optical system is the same for all configurations and is made by a pin-made integrated parabola and several coupling slots; it is used to shape and focus the energy coming from the input part to the radiating part. The antenna characteristics in terms of efficiency, bandwidth and scanning capabilities are compared. All the proposed antennas are low-cost, low profile, compact, efficient and very promising solutions for applications in the millimeter-wave range, especially for automotive radars.