linearization techniques for mixers

In the modern high-performance transceivers, mixers (both up- and down-converters) are required to have large dynamic range in order to meet the system specifications. The lower end of the dynamic range is indicated by the noise floor which tells how small a signal may be processed while the high end is determined by the non-linearity which causes distortion, compression and saturation of the signal and thus limits the maximum signal amplitude input to the mixer for the undistorted output. Compared to noise, the linearity requirement is much higher in mixer design because it is generally the limiting factor to the transceiver’s linearity. Therefore, this paper will emphasize on the linearization techniques for analog multipliers and mixers, which have been a very active research area since 1960s. The basics of the Gilbert mixer will first be covered. Once the source of nonlinearity is identified, different linearization methods, like the emitter degeneration, the feedback loop and the multitanh techniques will be discussed.