A self-packaged bandpass filter with controllable transmission zeros using Substrate Integrated Suspended Lines

A novel dual-mode circular patch resonator (DMCPR) is proposed to design a high characteristic bandpass filter (BPF) with controllable transmission zeros (TZs) based on Substrate Integrated Suspended Line (SISL) technology. The inherent degenerate modes of a circular patch adopted to achieve the DMCPR are separated and controlled by two embedded notches. Three TZs at upper and lower sidebands of the passband are introduced by the source to load coupling and can be adjusted by the separated electric and magnetic coupling (E/M) to improve the rolloff and rejection in stopbands. By making use of SISL, the implemented and fabricated 5.5GHz BPF, featured with self-packaging and low cost, achieves insertion loss (IL) of 1.44dB and fractional bandwidth (FBW) of 14.8% with compact size of 0.55λ
_g
×0.55λ
_g
(λ
_g
is the guided wavelength at 5.5GHz).