An Ultra-Wideband Filtering Hybrid Ring Coupler with Super Wide Upper Stopband

In this paper, a filtering hybrid ring coupler is proposed with an ultra-wideband passband and a super wide upper stopband. Both double-sided parallel-strip line swap phase inverter and electromagnetic bandgap structures are used. It takes the area of 0.92 × 0.7 λ_g² to provide a 110% wide passband centered at 1.55 GHz. Good in-band reflection, port isolation, magnitude and phase balances are achieved for both the in- and out-of-phase excitations. The rejection from the upper cutoff frequency to 20 GHz is over 20 dB.