Miniaturized IPD band pass filter with low insertion loss based on modified T-section for 5G applications

A miniaturized bandpass filter (BPF) with low insertion loss based on a modified T-section and a grounded transmission-zero resonator is proposed. The novel T-section consists of two resonators, which can achieve the bandpass performance with two transmission zeros (TZs) in the upper band. The grounded transmission-zero resonator can generate an extra transmission zero in the lower band. Therefore, high frequency selectivity can be achieved by the above three transmission zeros near the passband. The proposed BPF can achieve an insertion loss of 0.8 dB and a return loss of 22 dB covering 3.3–4.2 GHz, and the upper-stopband attenuation is better than 20 dB up to 12.5 GHz (3.3f₀). The proposed BPF with a miniaturized size of 1.2 mm × 0.5 mm × 0.3 mm have been fabricated using Si-based integrated passive devices (IPDs) technology and measured by on-wafer probing. The simulated and measured results of the proposed BPF are in reasonably good agreement.