Short stub band-pass filter using stepped impedance resonator for size reduction

This paper shows a short stub narrow bandpass filter using a stepped impedance resonator (SIR). A SIR is adopted instead of transmission line to reduce the size of the BPF on the low dielectric substrate. The size of the conventional narrow BPF is reduced by more than 30 % of its length of the transmission line within the inverter. The experimental results show that the insertion loss is 1.6 dB, return loss is 16 dB, and the fractional bandwidth is 10% at the center frequency of 5.8 GHz. The size of the filter is 22 × 8.7 mm².