Balun bandpass filter with wide upper stopband using silicon-based integrated passive device technology

In this work, a compact transformer-coupled balun bandpass filter is presented. The proposed balun bandpass filter features a compact chip size, and it can be designed according to the desired bandpass response and reference impedance. Specifically, a balun bandpass filter with 3rd-order bandpass response is demonstrated using the silicon-based integrated passive device process. The chip size is 2.5 mm×1.8 mm for a center frequency f0 of 2.4 GHz and a bandwidth of about 11.5%. The corresponding electrical size is only about 0.020λ0 × 0.014λ0 at 2.4 GHz. In addition, a wide 40-dB upper stopband from 3.76 up to 14 GHz is achieved.