Yig Dielectric Thin Films Phase Shifter Development

With the development of phased array radar,microwave communications,satellite communications and microwave measurement technology, the application of microwave phase shifters is wider. Many disadvantages are found on the traditional microwave phase shifters so several new types of which are developed to enhance the performance. The microwave dielectric film phase shifter is a member of the new types, the advantages of which are as following: microwave transmission loss is lower, the speed of phase shifting is faster,the microwave phase can be controlled by DC bias and the fabricating process can be compatible with the integrated circuit process. After the analysis of some structures commonly used in microwave dielectric film phase shifters, a new structure named distributed capacitor-loaded phase shifter is carried out. This kind of phase shifter's special characteristic is that the dielectric film of the periodically loaded capacitors is YIG film. The key research work include preparing YIG material via coprecipitation, calculating,modelling,simulating and testing the phase shifter and making a study of the fabricating process. Employing the formulation of theory analysis,software simulation together with manufacture of actual devices to do the work. Firstly, preparing YIG material and analyzing the five important factors of PH value,the speed of coprecipitation,sintering time,holding time and mixture ratio which influence the process greatly. Secondly, sputtering YIG on the Al2O3 substrate with RF-sputtering instrument and analyzing the film with AFM, the average grain size is 100nm and the surface roughness is about 10nm. Thirdly, using the engineering methods of coplanar waveguide with finite dimensions substrate and distributed capacitor-loaded phase shifter to calculate the phase shifter's size and realize impendence matching. Fourthly, simulating the phase shifter with HFSS9.0 and comparing the simulation results with the calculating results to improve on the designing. At last, fabricating the phase shifter with integrated circuit and thin-film process and then testing the device—the insertion loss is less than 10dB at the central frequency of 6GHz and the phase shift degree is about 20°of one single cell. There are some unconformities between the testing results and simulation results so finding the reasons and giving the direction to improve the property.