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VLSI Design
Volume 2007, Article ID 84650, 9 pages
http://dx.doi.org/10.1155/2007/84650
Research Article

A Q-Enhanced 3.6 GHz, Tunable, Sixth-Order Bandpass Filter Using 0.18 μm CMOS

1Department of Electrical and Computer Engineering, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 5A9
2Solido Design Automation Inc., Saskatoon, Saskatchewan, Canada S7N 3R3

Received 12 July 2006; Revised 20 November 2006; Accepted 11 April 2007

Academic Editor: Jose Silva-Martinez

Copyright © 2007 Anh Dinh and Jiandong Ge. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

An experimental filter was designed to operate at 3.6 GHz using mainstream 0.18 μm CMOS. In the design, the Q-enhancement technique was used to overcome the low-Q characteristics of the CMOS on-chip inductors. A sixth-order bandpass filter with a wide passband and a high image rejection was built by cascading three stages of second-order Q-enhanced filters. A combination of three biquads with offset in center frequency provides wider tuning frequency and bandwidth. This high-performance filter provides a 340 MHz tunable center frequency around 3.6 GHz, an image rejection of 50 dB and a tunable Q from 25 to 50 for a bandwidth adjustment from 95 MHz to 35   MHz. The filter achieves an 18 dB voltage gain while consuming 130 mW of power at 1.8 V DC supply. The chip occupies an area of 900×900μm2 including all the required bonding pads. The design provides a simple architecture to simplify tuning scheme for both frequency and bandwidth for practical use. The tunable ability of the design could be exploited in further study to be used as a channel-select filter in the gigahertz range.