Miniaturized, Low Loss Bandpass Filters Based on SISL Technology with Improved Stopband Rejection

In this paper, a self-packaged bandpass filter (BPF) based on substrate integrated suspended line (SISL) technology platform is proposed. The BPF is designed by using two quarter- wavelength stepped impedance resonators (SIRs) and one half- wavelength SIR. Three transmission zeros (TZs) at the upper and lower sidebands of the passband are introduced by the mixed coupling between resonators. By loading a capacitor in the half- wavelength SIR, improved suppression at the upper sideband is realized. The implemented BPF, featured with self packaging and a compact size of 0.34 is the guided wavelength at 6 GHz), achieves a low insertion loss (IL) of only 0.58 dB and fractional bandwidth (FBW) of 47.4%.