Compact Uniplanar Rat-Race Circuit Utilizing Shunt Capacitors and Crossover-Type Phase Inverter

This paper treats a rat-race circuit which plays combining/dividing of a microwave signal, and shows size-reduction and band-broadening design methods of the uniplanar circuit utilizing shunt capacitors and a crossover-type phase inverter. The designed circuit simultaneously realizes compact size and broadband characteristics. Next, we simulate the designed uniplanar rat-race circuit by using a commercial electromagnetic simulator in order to verify the design procedure and show broadband characteristics and flat couplings. Finally, experimental verification of the circuit at a center frequency of 2.4GHz is also described.