Miniaturized bandpass filter with ultrawide-stopband and high selectivity using glass-based IPD technology

A miniaturized bandpass filter (BPF) with ultrawide-stopband and high selectivity performance is proposed by virtue of glass-based integrated passive devices (IPD) technology. The proposed BPF consists of two modified second-order units and an impedance inverter. In the modified second-order units, two capacitors are added to the traditional second-order Chebyshev bandpass filter, which can generate two additional transmission zeros locating in the lower and upper bands, respectively. Moreover, these two modified second-order units are cascaded to improve the selectivity and achieve the ultrawide-stopband of the proposed BPF. In addition, the cascaded impedance inverter is introduced to further improve impedance matching of the proposed BPF. The proposed BPF is fabricated using glass-based IPD technology and measured by on-wafer probing. The fabricated BPF has a compact size of 1.0 mm × 1.0 mm × 0.35 mm. The measured results show that the fabricated BPF can cover the wide operating band from 3.3 GHz to 5.0 GHz with an insertion loss of 1.4 dB, a return loss better than 17.5 dB in the passband, and an upper stopband suppression better than 21.6 dB up to 43.5 GHz (10.48f₀). In addition, the fabricated BPF can achieve a good frequency selectivity with a rectangular coefficient of 1.33. The simulated and measured results exhibit good agreements.