Miniaturized Rat Race Coupler With Suppression of Spurious Passband

A new hybrid ring coupler design is devised for circuit miniaturization based on the periodic stepped-impedance ring resonator structure. The circuit has an area of 21.5% of a conventional rat race coupler and no passband up to the sixth harmonic of the design frequency. The designs are validated by comparing measured four-port parameters with the simulated results