Effect of Quality Factor on Center Frequency Deviation in Miniaturized CMOS Bandpass Filter.doc

Effect of Quality Factor on Center Frequency Deviation in Miniaturized CMOS Bandpass Filter In-Ho Kang, Shang-Ming Li and Young Yun( In this letter, the effect of quality factor on center frequency deviation in miniaturized coupled line bandpass filter (BPF) with diagonally end-shorted at their opposite sides and lumped capacitors is theoretically analyzed. The miniaturized BPF of a two-stage structure with two types of quality factors in standard CMOS process was designed and manufactured at 5.5 GHz. The die area of BPF was 1.44 ? 0.41 . The measured center frequency of BPF with a quality factor of 4.9 was deviated from 5.5 GHz to 4.7GHz. The one with 14.8 was shifted to 5GHz. The theoretical and measured results validate that quality factor influences the center frequency shift of BPF. Keywords: center frequency shifts, quality factor, shunt resonator, substrate loss, bandpass filter, CMOS. I. Introduction Bandpass filters are essential components in wireless communication circuits. RF transceiver development has been moving toward single-chip implementation, eliminating the discrete elements. Many BPFs have been published by CMOS technology, which has emerged as a viable system-on-a-chip technology that enables the full integration of RF integrated circuits. However, these filters have suffered from inherent losses with silicon substrate and low quality factor [1], [2], [3]. The miniaturized bandpass filter using diagonally end-shorted at their opposite sides and lumped capacitors showed more promise and a relatively higher quality factor than filters with the spiral inductors. [4]. However, the center frequencies of these filters are inclined to shift to the lower frequency. The greater difference in the center frequency of these filters between simulation and measurement in CMOS fabrication has not been analyzed until now. In this letter, miniaturized coupled line BPF with a two-stage structure by standard silicon integrated circuits was designed and manufactu