Research On 220GHz Image Rejection Mixer

Terahertz wave is an electromagnetic wave in a frequency of 0.1-10 THz,which has the advantages of both microwave and light waves.As "frontier of science and technology" and "major national demand",it is widely used in wireless communication,radar detection and military confrontation,which provides opportunities for technological innovation,social development and national security and promotes their development.Furthermore,the terahertz image rejection mixer,as the key core circuit of the solid-state transceiver front-end to realize frequency conversion,has attracted much attention from scholars at home and abroad with suppressing the image frequency and compact structure.This thesis firstly introduces the research background and related development trends of terahertz image rejection mixers,expounds the Schottky barrier junction,nonlinear characteristics and accurate modeling of planar Schottky diodes,and analyzes the working principle of harmonic mixing.Then,starting from the circuit structure of the image rejection mixer,the working principle of image rejection is analyzed,and the image rejection structure of the terahertz quadrature mixer and the IF 3d B quadrature coupler circuit is proposed.Secondly,the basic circuit topology of the quadrature harmonic mixer is analyzed,and the final topology circuit of the power and phase transformation of the RF and LO signals respectively through the 3d B quadrature coupler is obtained.Influence of coupler performance on two-way IF amplitude and phase unbalance of quadrature mixer is studied.Influence of amplitude and phase difference of two IF channels on image rejection is also studied.Finally,each circuit of the quadrature mixer is modeled by the co-simulation method of field-circuit combination and the best performance is obtained after several iterations of optimization.The terahertz image rejection mixer studied in this thesis is processed based on the domestic Ga As process.The test results are as follows: when the fixed local oscillator frequency is 110 GHz,in the 200-240 GHz band,the frequency conversion losses of the I and Q channels of the mixer are both less than 14.5 d B,the amplitude unbalance is less than 2d B,and the best typical value of the image rejection is greater than 10 d B.