Design Of Key Circuits For Local Oscillator Signals In Wideband Receivers

The continuous development of radar system,short-range wireless communication system,wireless local area network and other systems has greatly facilitated people’s life.RF front-end chip was the basis of wireless communication.RF transceiver affected the communication performance of wireless communication system.In order to support multi-band and multi-standard wireless communication in the future,UWB design has become one of the important research and trends.The local oscillator signal chain is the key of the receiver.In this thesis,the key technologies in the local oscillator chain of the receiver and millimeter wave broadband technology are studied,and the frequency multiplier chain,driver amplifier and polyphase filter are analyzed theoretically and the circuit design is carried out.The major work of this thesis is stated as follows:Aiming at the problems of low output power and low output frequency of local oscillator signals,a quadruple frequency chain was designed for the generation of local oscillator signals based on 45 nm SOI CMOS technology.The structure was composed of two stages of frequency doubler and one stage of common source driver amplifier,which generated output signals of 10 GHz～40GHz.The doubler adopted push-push structure,which can enhance the output power of the second harmonic by selecting the size of MOSFET reasonably and optimizing bias point.In order to convert a single-ended signal into a differential signal and achieve impedance transformation,the push-push based frequency doubler used a balun.The balun used a center-tapped capacitor to achieve AC ground and balance signals in the balun center.The simulation results showed that when the input power is 0 d Bm,the output power of double frequency ranges from 0.7 d Bm to 5.0 d Bm,and the fundamental suppression reaches more than 27 d Bc in the bandwidth.The output power of frequency quadrupler ranges from 0.9 d Bm to 6.8 d Bm,and the fundamental suppression is greater than 10.6d Bc.Based on the 0.13 μm Si Ge Bi CMOS technology,a wideband receiver oscillator local chain was designed.The circuit structure was mainly composed of two stages of driver amplifiers and polyphase filters.The passive polyphase filter used a three-stage cascade structure and generates quadrature signals in a wideband by setting three different pole frequencies.Considering the effect of passive parasitism on the amplitude and phase imbalance of the quadrature signals of the polyphase filter,this thesis changed the layout structure of the traditional polyphase filter through analysis,so that the passive parasitism was more evenly distributed in the I and Q signal and achieves a higher image rejection ratio.In order to compensate the loss of the polyphase filter and achieve larger gain and smaller gain fluctuation in the wide band,driver amplifier used differential cascode structure and RC parallel negative feedback technology.Driver amplifier used adaptive active bias circuit to solve the problem of static operating point instability of traditional bias circuit.The post-simulation results show that: In the range of 17 GHz～42 GHz,the image rejection ratios of the local oscillator chain of the receiver is larger than 36.8 d B,I signal and Q signal gain is more than 11.9d B,the S11 is less than-12.3 d B,the S22 and S33 is less than-10.7 d B,input 1d B compression point is more than-11 d Bm,The operating current is 40.3 m A.