Multi‐beam monopulse substrate integrated waveguide slot array antenna

Abstract

A multi-beam slot array antenna is proposed in the 10-GHz band for a monopulse tracking system with resolution enhancement techniques. The antenna architecture combines a four-subarray substrate integrated waveguide (SIW) slot antenna, a multi-beam-forming network of microstrip Rotman lens array, and a SIW comparator of four-quadrant monopulse technique. A method to form difference patterns in both E-plane and H-plane for mutibeams is presented, and the method can improve the accuracy of angle detection for all beams. The key point of the method is to compensate the phase difference caused by the beam deflection between the two subarrays (quadrants) by constraining input delay lines of the Rotman lens array. To validate the proposed concepts, an antenna prototype is realized and measured. The experimental results demonstrate a scanning range of ±36° with -5 dB crossover level between two adjacent sum beams in the E-plane. The corresponding difference patterns are generated in both E-plane and H-plane via the monopulse comparator. The multi-beam monopulse system can achieve gains between 21.7 and 23.5 dBi for all sum beams at the center frequency of 10 GHz. This multi-beam monopulse slot antenna can be applied in radars and communication systems requiring beam-scanning capabilities and target tracking.