Research And Design Of Broadband Microstrip Transition Structure

This thesis aims to give theoretical analysis and innovative research on traditional transitions in microwave/millimeter-wave systems including microstrip-to-microstrip vertical transition, microstrip-to-CPW transition and microstrip-to-CPS transition. In order to increase the bandwidth and gain good impedance-matching, we utilize the low-impedance microstrip stubs and stepped impedance slotline stubs in the design thus to reliaze microstrip-to-microstrip vertical transition based on the microstrip-to-slotline transition form. In order to increase the passband bandwidth, we design the microstrip-to-CPW transition based on electromagnetic coupling of microstrip and CPW. Furthermore, a high characteristic impedance short-ended stub paralleled with microstrip main transmission line is also introduced. In order to realize wideband and compact design for the microstrip-to-CPS transition, microstrip line and coplanar strip line are selected to locate on both sides of the dielectric substrate. By Using magnetic coupling, the transition is finally realized. In this design scheme, field matching and impedance matching sections are successfully avoided.Based on the theoretical analysis and the simulation by the three dimensional electro-magnetical simulation software (HFSS), theoretical verification for our proposed new transition structure are presented. Bisides, fabrication and experimental measurement of the microstrip-to-microstrip vertical transition and the microstrip-to-CPW transtion are also supplied. For the microstrip-to-microstrip vertical transition, simulated and measured results show that a bandwidth of2.3-14GHz (143%) with return loss better than10dB and insertion loss below2dB can be achieved. For the microstrip-to-CPW transition, simulation and test results indicate that a bandwidth of2.6-12.2GHz (129%) with return loss better than10dB and insertion loss below1.7dB can be achieved. For the microstrip-to-CPS transition, simulation results show that a bandwidth of5.5-18.3GHz(107%) with return loss better than10dB and insertion loss below3dB can be achieved. Results indicate that the three transition structures presented in this thesis have the features of wide bandwidth, low insertion loss, and compact structure. These transitions are suitable and valuable for application in the microwave integrated circuits such as monolithic integrated circuit (MMIC).