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

Abstract

This letter presents an on-chip ultra-wideband (UWB) bandpass filter (BPF) in 0.18- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> 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 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> 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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}\,\,\times 428\,\,\mu \text{m}$ </tex-math></inline-formula> excluding testing pads.