High-linearity folding image mixer

Abstract

The invention relates to a high-linearity folding image mixer which is of a structure characterized in that a double-balanced switch pair is embedded in a current mirror. Under the combined operation of the current mirror and the double-balanced switch pair, an intermediate frequency current signal is generated from a transconductance radio frequency current after the frequency conversion, wherein the size of the intermediate frequency current signal has an image proportional relation with the radio frequency current; and then an output voltage is formed on a load resistor by the current. Dueto the proportional replicating property of the current mirror, the mixer has better linearity than that of a Gilbert mixer of a folding structure. In addition, the traditional mixers are mainly of astacked structure of transconductance, mixing switch pair and load phase from a power supply to the ground. In the mixer provided by the invention, a parallel cascade of transconductance, mixing cascade and load phase is realized, and the mixer is suitable for low supply voltage applications.

Description

technical field [0001] The invention relates to a high-linearity folding mirror mixer, which adopts a structure in which a pair of double-balanced switches are embedded in a current mirror. It has the characteristics of large conversion gain, high linearity and suitable for low power supply voltage. Background technique [0002] In the RF signal receiving chain, the role of the mixer is to down-convert the input RF signal to baseband or intermediate frequency for subsequent modules to process. As a consideration of the entire receiving chain, the mixer should have a high conversion gain to suppress the impact of the noise of the subsequent intermediate frequency amplifier circuit and filter circuit on the noise figure of the entire receiving chain. In addition, the mixer itself should have a lower noise figure than the IF module to relieve the design pressure of the low-noise amplifier. With the application of multi-carrier technology and complex modulation technology in w...

AI Technical Summary

Problems solved by technology

However, due to the limited output impedance and parasitic capacitance of the transconductance transistor, there is a shunt phenomenon of RF current between the transconductance stage and the local oscillator stage.

The entire folded mixer can be regarded as a cascade of the transconductance stage, the local oscillator stage and the load stage. According to the linearity cascade formula, the linearity of the entire mixer is deteriorated

This is also the main reason why the linearity of the folded structure is not high

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