Ultra-Wide Stopband Bandpass Filter Using Second-Order M-Type Circuit Based on Glass-Based IPD Technology

An ultra-wide stopband bandpass filter (BPF) using second-order M-type circuit is proposed by virtue of glass-based integrated passive device (IPD) technology. The second-order M-type circuit is composed of two first-order M-type circuits in series. The first-order M-type circuit consists of a low-pass filter (LPF) and a high-pass filter (HPF), each of which can generate one transmission zero. The second-order M-type circuit can generate two transmission zeros in the low frequency band and another two transmission zeros in the high frequency band, which can achieve high rejection in the upper ultra-wide stopband. The proposed BPF covering 3.3–4.2 GHz is fabricated with a compact size of 1.0 mm × 1.0 mm × 0.3 mm on glass-based IPD technology. According to the measurements, the fabricated BPF can achieve a minimum in-band insertion loss less than 1.4 dB, a return loss better than 15.6 dB, and more than 20 dB ultra-wide stopband rejection from 5.81 to 43.5 GHz. Compared to the previous designs, the proposed BPF shows the superior advantages of compact size and ultra-wide stopband.