Compact tunable wideband bandpass filter using mixed coupling lumped dual-mode resonator

摘要

In this paper, a compact microstrip varactor-tuned wideband bandpass filter (BPF) is proposed by using mixed coupling lumped dual-mode resonator. The proposed tunable wideband BPF has a pair of transmission zeros around the passband, resulting in high passband selectivity. The measured results show that the passband can be tuned in a frequency range from 1.01 to 2.04 GHz with an almost 3 dB constant fractional bandwidth of 28 +/- 1%. Within the tuning range, the insertion loss varies from 2.1 to 1.65 dB and the return loss is better than 10 dB. In addition, the tunability of 3dB fractional bandwidth at 1.5 GHz is from 23 to 43%.