| The growing demand for voice and data communication systems has created a need for low-cost, low-power, high dynamic range radio-frequency (RF) front-ends. In RF receivers, mixers translate the incoming signal frequency from RF to baseband, where information is easily recovered. The dynamic range of a receiver is determined by its noise figure and the intermodulation (IM) distortion products it generates. The IM response of the receiver chain is usually dominated by that of the mixers. Thus, there is great interest in the design of high dynamic range mixers. Currently, high dynamic range mixers are implemented in GaAs technology. Modern sub-micron CMOS technology is an attractive alternative because it provides lower manufacturing costs and the ability to integrate the RF functions and the base-band processing circuitry on the same chip. The focus of this research is the analysis and implementation of high dynamic range mixers using a standard CMOS process.; The goal of this research is to help designers realize high dynamic range mixers in a standard CMOS process. In particular, we concentrate on passive mixers since they can achieve levels of intermodulation distortion significantly lower than active versions. The passive mixer topology studied here is the resistive ring mixer. We derive equations for the mixer transfer function, conversion gain, and noise figure. Also, we describe the generation of the intermodulation distortion in the mixer, and discuss design and optimization techniques. Then we demonstrate the feasibility of using CMOS technology for a high dynamic range mixer by building a broadband up-conversion mixer for cable modem applications. |
