| Summary: | 碩士 === 逢甲大學 === 電機工程學系 === 107 === Modern communication systems are setting more and more requirements for circuit components. Components such as filters and power splitters/combiners are usually designed and manufactured individually in the past. High integration circuit components, on the other hand, integrates several functions into a single circuit to reduce the number of circuits in a system, is the trend of current developments. This thesis aims at the integration of a rat-race coupler and a filter into a single device, and make its passband frequency reconfigurable.
In this thesis, two designs using different feeding methods are proposed for the coupled resonator network which provides the function of rat-race coupler with filtering responses. The first method is direct feed, which is fed directly from four input/output (I/O) ports to the four resonators, This method requires designing DC block circuits at I/O ports so that DC current does not flow back into the vector network analyzer (VNA). The second method is coupled feed, which uses four L-type coupling structures at I/O ports to the four resonators. The coupled feeding strutures prevent DC current flowing back into the VNA, which result in a simpler circuit design.
Both methods simultaneously achieve a 0 and a 180 degrees power splitting/combining function by a highly symmetrical structure. In addition, the coupling structure satisfies the coupling coefficients and external quality factors of a second-order Chebyshev filtering response, making the structure exhibit filtering function. The proposed coupler is mainly used at a center frequency of 2.45 GHz. In order to make the passband frequency tunable, a varactor (MA46H120) is added to the ends of all coupled resonators. By changing the capacitance value through different bias voltage, the resonator frequency can be changed, thus the passband frequency of the proposed circuit can be reconfigured. The range of reconfigurable passband center frequency is between 2.34 GHz and 2.57 GHz.
|
|---|
