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Unformatted text preview: IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS—II: ANALOG AND DIGITAL SIGNAL PROCESSING, VOL. 46, NO. 3, MARCH 1999 231 Monolithic RF Active Mixer Design Keng Leong Fong, Member, IEEE, and Robert G. Meyer, Fellow, IEEE Abstract— An overview of monolithic radio-frequency (RF) ac- tive mixer design is presented. The paper is divided into two parts. The first part discusses the performance parameters that are relevant to the design of downconversion mixers, and how they affect the system performance. The second part presents three common kinds of mixer topologies, namely, unbalanced, single- balanced, and double-balanced designs. This paper concentrates on active mixers only. The advantages and disadvantages, as well as the design and optimization techniques for the three kinds of mixers, are discussed. Index Terms— Analog integrated circuits, circuit optimization, MIMIC’s, MMIC circuits, mixers, nonlinear circuits. I. INTRODUCTION T HE rapid growth of portable wireless communication systems, such as wireless (cordless and cellular) phones, global positioning satellite (GPS), wireless local area network (LAN), etc., has increased the demand for low-cost and high- performance front-end receivers. This presents a challenge to radio frequency (RF) circuit designers to find optimal solutions for the realization of high-frequency (900 MHz to 3 GHz) receivers using low-cost plastic packages and high-volume silicon technologies. Fig. 1 shows a typical RF receiver front-end architecture. The downconversion mixer is used to convert the RF signal down to an intermediate frequency (IF) by mixing the RF signal from the low-noise amplifier (LNA) with the local oscillator (LO) signal. This allows channel selection and gain control at lower frequencies where high quality-factor ( ) filters and variable-gain amplifiers can be constructed eco- nomically. Instead of using an IF filter with tunable passband frequency, an IF filter with fixed passband frequency is used, and the LO frequency is tuned to select the desirable channel. The LNA is used to amplify the RF signal to reduce the noise contribution from the mixer. The RF and image-rejection filters are used to reject undesired out-of-band signals. The downconversion mixer is a very important building block because its performance affects the system performance and the performance requirements of its adjacent building blocks, which include the LNA, LO, RF filter, image-rejection filter, and IF stages. Manuscript received July 31, 1997; revised February 23, 1998. This material is based on work supported in part by the U.S. Army Research Office under Grant DAAH04-93-F-0200. K. L. Fong was with the Electronics Research Laboratory, Department of Electrical Engineering and Computer Science, University of California, Berkeley, CA 94720 USA. He is now with Philips Semiconductors, Sunnyvale, CA 94088-3409 (e-mail: [email protected])....
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