Integrated Rf Active Mixer Noise Analysis

An active mixer is widely used in most electronic systems with the function of the frequency translation and considered to be one of the key blocks. Noise characteristics of an active mixer will seriously affect the overall system performance, such as the sensitivity, dynamic range (DR), selectivity, etc.. Therefore it is crucial to analyze and predict the noise characteristics of active mixers.It is well known that transistors are the dominant noise contributors of active circuits. The transistors have various noise sources including the thermal noise, flicker noise, shot noise, etc.. The analysis of noise characteristics of active mixers in the literature is commonly based on the available transistor noise models published in the literature for individual un-coupled noise sources. However, the transistors of an active circuit must be biased and operated under certain voltage conditions. The noise characteristics of any active circuits must be operation-voltage-dependent. Unfortunately, there was lack of the noise-coupled model including the operation-voltage-dependence in the past.Recently, the drain-source-voltage-dependent transistor noise model with the coupled channel thermal and shot noises has been developed, providing the possibility to discuss the voltage-dependent noise characteristics of active CMOS mixers with the coupled noise sources. In this thesis, the noise characteristics of active CMOS mixers are systematically analyzed employing this transistor noise model. The analytical expressions are derived to capture the noises originating in different parts of the mixer. Explicit expressions of the output added noise and noise figure considering the coupled thermal- and shot-noise are presented. Basing on the expressions derived in this thesis, a proto-method has been developed to predict the noise characteristics of the active CMOS mixers under real operating conditions.According to the authors'knowledge, this thesis for the first time clarifies the influence of the operation voltages of the MOSFETs on the output noise of the active CMOS mixers theoretically.