Quarter-wave parallel-coupled and interdigital microstrip bandpass filters with generalized chebyshev response

Two quarter-wave resonator microstrip bandpass filters with generalized chebyshev response are proposed in this work. By using the delay lines and observing the phase relationship between source and resonators, the phase and amplitude of cross couplings can be easily realized so that a generalized chebyshev response can be implemented. Furthermore, the cross coupling for interdigital structure is proposed. Finally, a 3rd-order high selectivity quarter-wave filter and a 5th-order high selectivity and flat group delay interdigital filter are fabricated to show the feasibility.