Compact monopulse sum‐difference comparator based on double‐layer substrateintegrated waveguide

Abstract

A monopulse sum-difference comparator based on double-layer substrate integrated waveguide (SIW) for X-band applications is investigated and experimentally validated. A 90° 3-dB directional coupler with a double-stepped coupling slot in the common broad side between a pair of folded parallel SIWs and an equal-length unequal-width 90° phase shifter are adopted to form a magic tee. The four magic tees are elegantly interconnected to design a highly compact comparator. Experimental results show the bandwidth (reflection coefficient < −10 dB) of the comparator can achieve 10% with an operating frequency range of 9.5–10.5 GHz, in which the output amplitude and phase imbalance are within 0.75 dB and 14° (RMS), respectively. The insertion losses are about 1.5–2.5 dB and the isolations between the three channels are all better than 20 dB. In particular, the double-layer configuration of the comparator network reduces the occupied area with the potential for high integration and makes it to be a good candidate for miniaturised and compact monopulse antenna systems.