Self-Packaged Dual-Band Filter with High Selectivity and Low Radiation Loss

In this paper, a self-packaged high-performance dual-band filter based on shielded substrate-integrated stripline (SSIS) is proposed. The fully enclosed 4
^th
-order dual-band filter is shielded in a substrate-integrated cavity composed of a group of shielding vias and two metal shielding layers. The dual-band filter is developed by specified quasi-elliptic filtering response and implemented by two independent coupling paths including both single- and dual-mode stepped impedance resonators (SIRs). Four transmission zeros (TZs) generated by cross couplings further enhance the selectivity, and they can be controlled by altering the related coupling coefficient. For demonstration, a filter prototype is designed, fabricated, and measured. The synthesized, simulated and experimental results show good agreement. Compared with recently published literatures, the proposed filter features advantages in terms of low radiation loss, self-packaging, high selectivity, and easy fabrication.