Compact GaAs-Based Bandpass Filter Using Symmetric Multi-Stub Resonator

Abstract

In this paper, a symmetric multi-stub resonator (SMSR) is proposed for the design of millimeter-wave on-chip bandpass filters (BPFs) with wide bandwidths, low insertion losses (ILs), and compact sizes. The multimode resonant characteristics are investigated and can be adjusted by varying the dimensions of the SMSR, enabling flexible control of the filtering responses. To validate the proposed idea, two BPF prototypes are designed and fabricated using a 0.25-<inline-formula> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula>m gallium arsenide (GaAs) process. The measured results show that the fabricated devices operate at center frequencies of 51.3 GHz and 52 GHz, with 3-dB fractional bandwidths of 24.8% and 25.5%, and minimum in-band ILs of 1.07 dB and 1.1 dB, respectively. Excluding the G-S-G pads, the two proposed BPFs occupy core areas of only <inline-formula> <tex-math notation="LaTeX">$0.063~\lambda _{0} \times 0.042~\lambda _{0}$ </tex-math></inline-formula> and <inline-formula> <tex-math notation="LaTeX">$0.063~\lambda _{0} \times 0.055~\lambda _{0}$ </tex-math></inline-formula>, respectively.