The Research Of The MEMS Reconfigurable Directional Couplers

Based on the theories of asymmetric coupled lines, RF MEMS switches and floating-plane overlay technology, a novel reconfigurable directional couplers with integrated MEMS switches are investigated in this thesis.During the past years, the reconfigurable devices, such as reconfigurable MEMS micro-strips and reconfigurable MEMS microwave-filters, have drawn growing attention, due to the availability of MEMS switches with high performance. However, as an important microwave device, directional coupler, especially the reconfigurable MEMS parallel line directional coupler with strong coupling, has not received enough concentration. Therefore, some efforts have been made to research and develop the reconfigurable MEMS parallel line directional couplers with high coupling coefficient.In the thesis, the latest researches of reconfigurable directional couplers inside and outside the country has been presented and analyzed firstly. Secondly, according to the theory of asymmetric coupled lines, a new kind of reconfigurable directional coupler with MEMS switches is designed. The simulated results show that the reconfigurable couplers can be realized by changing the distance between the coupled lines and the width of the coupled lines. Finally, according to the theory of the floating-plate overlay, the coupling between the lines can be enhanced greatly by placing a piece of floating metal plate on the parallel coupled micro-strip lines. The research shows that the parallel-lines directional couplers with 3dB coupling coefficient can be achieved, and the coupling coefficient of the original coupling port can be more than 3dB, which makes it become the through port, and the original through port become the coupling port. Therefore, the reconfiguration of the coupled port is realized. This reconfigurable MEMS coupler has four working states with the S31 of -3.5dB, -3.18dB, - 3.01dB, -2.63dB respectively, and the size is just 10.2*31.6mm~2.