The Design Of Up-conversion Mixer Fit For WCDMA Based On0.18μm Technology

With the rapid development of Internet and mobile communication technology,people expect higher wireless transmission rate.WCDMA receive widespreadattention because it can provide high data transfer rate. The most important module ofthe wireless communication system is the radio frequency integrated circuits. Withthe development of CMOS technology RF circuit developed into a low-cost andlow-power integrated circuit from discrete devices.The mixer is an important moduleof the RF receiver and transmitter. Mixer performance can directly impact whether thewhole system can work well.The main kinds of transmitter structure are direct frequency conversion transmitter and heterodyne transmitter, the output efficiency power,linearity,frequency stability,operating frequency,and spurious suppression and emission spectrum purity parameter of transmitter determines the pros and cons of transmitter.Design in this paper applies to the up-conversion of WCDMA which is one kind of direct frequency conversion transmitter.The direct frequency conversion transmitter mainly consist of there parts: baseband signal processing, mixers and power amplifiers. Carried out a detailedstudy for the mixer.The mixer is designed on the basis of the multiplier, to realize the frequencyconversion function.The mixer can be divided into active mixers and passive mixers.Its main performance parameters are conversion gain, noise figure, isolation andlinearity.Double-balanced active Gilbert structure is the basic circuit structure for themixer design and improvement.A lot of good performance mixer is designed based onthe structure.The main design part of this paper is based on the structure, introducethe current injection technique,set the bias circuit and RF output impedancematching,design full function of the mixer.Base on0.18μm SiGe BiCMOS process tocomplete the final circuit layout design.Post-layout simulation on parameters andperformance of the mixer, simulation results show that the circuit conversion gain of0.1dB,the noise figure is12.9dB,The compression point of1dB is-12.3dBm, outputpower is-17.79dBm.And S11is-13.85dB.Its parameters and performance meet therequirements of design.Meet the actual use requirements.