Compact L-band Microstrip Bandpass Filters on Titanate-based Substrate

This paper presents a compact microstrip bandpass filter (BPF) for L-band wireless applications. The titanate-based substrate with a high dielectric constant of 135 is used to reduce the size of the BPF that is fabricated by the thin film process. The Miniaturization leads to multiple cross coupling effects, which introduces out-of-band transmission zeros. The L-band microstrip BPF has been designed, fabricated and tested, which has a small size of 3.2×5×0.18 mm
³
. The simulated and measured results show that two transmission zeros locate at the both sides of the passband and the insertion loss of the BPF is less than 2.5 dB at central frequency while the out-of-band suppression is more than 50 dB.