| Summary: | 碩士 === 國立臺灣海洋大學 === 電機工程學系 === 93 === The micro-coplanar striplines have the same advantages of coplanar waveguides, such as the low dispersion, low power loss, easy of shunt connection, and eliminating the need of via holes. Because the micro-coplanar stripline lacks one upper ground plane as compared with the coplanar waveguide, it can avoid exciting extra slotline-mode surface wave and can reduce the size of the circuit. Furthermore, the defected ground structure not only can improve the performance of the filter, but also can furtherly reduce the size of the circuit. Therefore, in this thesis, the micro-coplanar striplines with defected ground structure are used to design the lowpass filters.
In this thesis, the basic characteristics of the micro-coplanar striplines and the influence of defected ground structure are analyzed firstly. Next, the design theory of the lowpass filter using micro-coplanar striplines are studied, and the equivalent circuit of defected ground structure is derived. Finally, the lowpass filters using the stepped-impedance structures or the T-junction structures are designed and realized, respectively. In addition, the characteristics of these two filters are measured and compared with the simulation results.
From the analyzed results, it is noted that both two lowpass filters have good performance. In addition, if the defected ground structures are used, the size of the circuits can be reduced about 16% and 15% for lowpass filters using the stepped-impedance and T-junction structures, respectively.
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