| Summary: | 碩士 === 明新科技大學 === 電子工程研究所 === 94 === Filter plays an important role in radio frequency front-end circuit of communication system. Regarding the communicatory receiver or transmitter for different frequency channel. We must insure that the integral data and there will not be influenced by other signals. For this reason, we have adopted different kind of filters to insulate the signals from other frequency channel. In the recent years, the mobile communications have developed rapidly, the trend of every devices of communicatory product are also more and more small. In order to be small frame, low cost, and easy to integrate with integrated circuit. In this thesis, we choose plane dual-mode band-pass filter to as be a basic structure. Its characteristic is to produce two transmission zeros, they could let stop-band attenuation faster on either side of the passband. But this structure also will produce harmonic. In order to reject harmonic, we introduced into defected ground structure（DGS）. Using the eliminated frequency characteristic to reject harmonic without increasing circuit size to become stop-band. Furthermore, we try to design a resonator structure on this circuit. Using this resonator structure to become another width passband to make a dual-band filter with defected ground structure.
We simulated best circuit design by simulation software IE3D and FR-4 substructure to complete the results between simulator and measurement. We can get a better performance such as simulator. This method is suitable function to reduce the filter size.
Keywords：filter、dual-mode、transmission zero、harmonic、defected ground structure
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