Design of quad-channel diplexer using short stub loaded resonator

Compact quad-channel diplexer (2.5/3.5GHz and 3/4GHz) using meandering short stub loaded resonators is proposed. The quad-channel diplexer is composed of two pairs of coupled short stub loaded resonators to obtain independently controlled bandwidth at each passband and to reduce the circuit size. In addition, the mixed electric and magnetic coupling is employed to create a desired transmission zero in the stopband, thus improving the isolation between each two passbands. The proposed diplexer is in final fabricated and measured. A good agreement between simulated and measured results evidently validates the proposed methodology.