Research Of Key Techniques In K-band CMOS Receiver Front-end

Satellite communication,as the main way of wireless communication,is widely used in the military and commercial fields because of its communication distance,wide coverage area,wide frequency bandwidth and strong stability.With the gradual expansion of the application,satellite communications aim to the higher frequency band,higher quality,"communication in moving" and other direction.Transceiver front-end chip is an important part of the satellite communication system,its performance will directly affect the entire system.The main performance of receiver front-end include power gain,noise figure,linearity,integration,power consumption and so on.The traditional millimeter-wave receiver front-end mostly composed of discrete devices,with high cost,large size,difficult to integrate and other shortcomings.Silicon-based CMOS process,not only with low cost and low power consumption,but also can integrate analog circuits,RF circuits and digital circuits at the same time in one chip,in order to achieve smaller size.This paper is based on the standard CMOS technology to study the key technologies in the K-band receiver front end,realize the key modules,the single-channel receiver front end and low noise down-conversion channel front end.Firstly,this paper presents the research background,the situation of the receiver front-end,and the overview of the main performance indicators.The research adopts the top-down and bottom-up research process.First,planning the whole architecture according to the requirements of the system,and then,determine the module composition and each module's performance,determine the research direction to the key technology of the receiver front end.After all modules had been fabricated and test,some of them were integrated into a singlechannel chip to realize the low noise,low power consumption and high performance front-end.This paper concentrated on the key modules of low noise amplifier,attenuator,mixer and frequency doubler in RF front end.In the study of low noise amplifier,this paper introduces the calculation method of noise figure and gain,gives the method of selecting proper size of the MOSFETs at the operating frequency,and how to optimize noise figure and gain according to current density.Then,the circuit design and layout design of K-band low noise amplifier based on 90 nm CMOS technology are given.In the design process,the source degenerate inductor and the matching capacitor are very small,and how to achieve them accurately is also an important part of the design.In the study of attenuator,this paper introduces the different structures of step attenuators,and analysis their advantages and disadvantages.Finally,the X-type attenuator is selected for design.The X-type attenuator achieves the attenuation by using a transistor operating in the linear region.The on-resistance of the linear region is related to the threshold voltage which changes in different process corner,thereby affecting the attenuation accuracy.Therefore,this paper come up with a compensation method,which uses the output voltage of the source follower to cancel the threshold voltage in the on-resistances,so that alleviating the attenuation changes caused by process variations.Finally,the whole circuit and layout design of K-band X-type step attenuator based on 90 nm CMOS process is completed.In the study of mixer,which is an important modules in the receiver front-end,this paper introduce the classification of mixer and select the fully balanced active structure to design.Giving the method of choosing transistors' size and the bias voltages,and realizing the circuit and layout design of K-band down-mixer based on 90 nm CMOS technology.When RF signal and the LO signal frequency are the same,the mixer can work as a frequency doubler.But due to the time-delay of the transconductance transistor,the signal in differential output ports are not balanced.Therefore,this paper raises a compensation method,using two Gilbert cell fed with differential quadrature signal respectively to cancel the imbalance at the output ports,thus realizing the full-balanced differential doubler.In the design process,the quadrature signal generation is also an important part of the study.Finally,the paper gives the circuit and layout design of the truly balance doubler based on the 90 nm CMOS process.Finally,all modules has been fabricated and test,this paper present the test methods of different circuits.The results of each module are in accordance with analysis and simulation results.At the same time,some modules are integrated into one chip to realize the singlechannel RF front-end,which has also been fabricated and test.Every chip achieves the desired results,can be widely used in K-band receiver design.