A Quasi-Box-Like Dielectric Filter Sharing a Cavity With Wide Stopband

A dielectric filter using a shared cavity with a quasi-box-like topology is proposed. In the shared cavity, four TE101 mode resonators with a dispersive coupling are cascaded to obtain a quasi-ellipse response. A coupling iris is employed to isolate cross coupling and provide source-load coupling based on the absorption effect of dispersive coupling on cross coupling while not on source-load coupling. This design offers a controllable transmission zero (TZ) which extends the stopband up to $1.85~f_{\mathbf {0}}$ with rejection greater than -20 dB. A design example is fabricated and measured. The simulated and the measured results show good consistency for validating the wide out-of-band suppression characteristics of the proposed filter.