Design Of Image Rejection Mixer For GNSS

As the global satellite navigation system is becoming more and more widely used in our daily life,the requirement for the performance of radio frequency chips for satellite navigation receivers are becoming higher and higher.It is a problem for the circuit designer that the image interference signal is hard to eliminate during the design.The image rejection mixer based on the Hartely structure is proposed.It realizes the good suppression of the image interference signal by the optimized mixer core structure and the passive multiphase filter.In this paper,firstly,the development statue of the global satellite navigation system and the mixer is introduced,then several receiver structures and image suppression structures are described.On the basis of this,the principle,index and classification of the common mixer are introduced in detail.A high image rejection ratio?high conversion gain,good linearity and good single-side band noise factor image rejection mixer is proposed.It is made up of the buffer circuit module,mixer core module,passive multiphase filter module,summing circuit module and the bias circuit module.Especially,a common radio frequency input structure is adopted to improve the matching degree of the circuit structure to optimize the image rejection effect.This image rejection mixer can be used in the dual mode satellite navigation receiver for GPS L1(1575MHz)and BD B1(1561MHz).The circuit is designed by TSMC 0.18?m COMS process.It is simulated by the Spectre in Candence which indicates that intermediate frequency output signals are both 4MHz for B1 and L1 bands.The image rejection ratio for B1 and L1 bands are both 40.5d B.The conversion gain are both 23.8d B.The input 1d B Compression point are both-23.3d Bm.The single-side band noise factor are both 15.2d B.