An On-Chip Ultra-Wideband Bandpass Filter in 0.18-μm SiGe BiCMOS Technology

This letter presents an on-chip ultra-wideband (UWB) bandpass filter (BPF) in 0.18-
$\mu \text{m}$
SiGe BiCMOS Process. The proposed UWB BPF is constituted by cascaded quasi-elliptic response high-pass filter (HPF) and low-pass filter (LPF). A series
LC
circuit is introduced in the classical fifth-order lumped-element HPF, so that a transmission zero (TZ) is generated to form quasi-elliptic response. The microstrip line LPF with two series of open stubs can generate another two TZs, which also result in quasi-elliptic response. Step-to-step design procedure is given to guide the UWB BPF design. The measured result shows that the fabricated UWB BPF covers the frequency range of 10 – 50 GHz with the in-band return loss better than 13.5 dB, and the minimum in-band insertion loss is 1.99 dB. The core size of fabricated UWB BPF is 382
$\mu \text{m}\,\,\times 428\,\,\mu \text{m}$
excluding testing pads.