An experimental investigation of a novel compact microstrip 180 degrees rin
g hybrid incorporating a one-dimensional (1-D) slow-wave structure, in the
form of perforation on the ring itself, is presented. The size of the hybri
d is reduced by 23% due to the slow-wave effect, and this size reduction te
chnique has potential applications in MICs and MMICs, The measured insertio
n loss is comparable to that of a conventional microstrip hybrid.