Design of a multilayer miniaturization rat-race

A compact microstrip rat-race hybrid with a wideband characteristic and a miniaturized area employing microstrip lines and strip lines circuit is reported in this paper. The proposed hybrid has been fabricated with a multilayer print circuit board technology to benefit from a high level of integration. The footprint of the proposed design occupies 50% of the area of the conventional similar design. Across the frequency bandwidth, the maximum amplitude unbalance is 0.5 dB, the isolation is better than 20 dB. Moreover, the circuit is planar, easy to application because of the sum port and difference port located on the same side. It is believed that this circuit has the best size reduction for wide-band rat-race couplers in open literature. The measured results show good agreement with simulation responses.