High-linearity frequency mixer in radio frequency identification

Abstract

The invention discloses a high-linearity frequency mixer in radio frequency identification. The high-linearity frequency mixer comprises a load circuit, a switching circuit and a transconductance circuit, wherein the switching circuit is connected with the load circuit, and the joint of the switching circuit and the load circuit is provided with a signal output end; the switching circuit comprises a first current path; the transconductance circuit comprises two input transconductance pipes which are connected in parallel; each transconductance pipe is connected to the first current path; the signal input end of each input transconductance pipe is respectively connected with a bias resistor, and the bias resistor of each input transconductance pipe is respectively connected with a bias voltage; and the signal input end of each transconductance pipe is further respectively connected with an input blocking capacitor, and each input blocking capacitor is connected with a radio frequency signal. The high-linearity frequency mixer disclosed by the invention can be used for improving the linearity of the frequency mixer, improving the capacity of processing large signals and further improving the conversion gain of the frequency mixer.

Description

technical field [0001] The invention relates to a mixer, in particular to a mixer with high linearity in radio frequency identification. Background technique [0002] In the radio frequency identification (RFID) communication system, the mixer is one of the most important circuit modules. It converts down to obtain an intermediate frequency or zero frequency signal, and converts up to obtain a radio frequency signal. Because the mixer has signals of two frequencies, and the RF signal has been amplified by the low-noise amplifier, the requirements for linearity and other indicators are relatively high. For the mixer circuit, there are generally two structures, one is an active mixer, namely the Gilbert structure, and the other is a passive mixer. Active mixers have better noise figure and gain, while passive mixers have higher linearity, so it is difficult to design active mixers with high linearity. [0003] like figure 1 As shown, it is a circuit diagram of an existing G...

AI Technical Summary

Problems solved by technology

The linearity of the existing Gilbert mixer mainly depends on the input stage transconductor, namely the NMOS tube M 1 , when the input stage transconductor input signal, that is, the radio frequency voltage signal RF is small, the output small signal current, that is, the radio frequency current signal and the input small signal voltage present a good linear relationship, but as the input signal amplitude increases Large, the transconductance changes with the input signal, so the output current does not change linearly with the input voltage, so the linearity becomes worse

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