| Summary: | 碩士 === 國立勤益科技大學 === 電子工程系 === 105 === A compact band rejection structure is proposed, Two types were designed. Type-one is microstrip in-line two-line band rejection structure, it simply consists of two transmission lines and with one of the transmission line serial connected with a reactive element capacitance or inductance. It can be designed directly into 50 ohm line layout. Using the basic circuit theory to analyze the proposed structure, a design equation is obtained for determining band rejection frequency. Varying the reactive element value or transmission line characteristic length will change the band rejection frequency, this flexibility allows the possibility of rejecting the unwanted signal at the existed transmission line easily.
Type-two is microstrip in-line three-line band rejection structure, it consists of three parallel lines with one thru line and two lines left a gap at the end of line. Both type-one and type-two are designed directly on 50 ohm line layout., Varying the reactive element value or transmission line characteristic length will change the band rejection frequency. The microstrip in-line three-line band rejection structure have better bandwidth than the two-line approcach.
In this thesis, we aualyse band rejection structure using the ABCD formula, then the related deriving Y parameters and finally converting Y to S parameters. The circuit design has been designed, simulated, and fabricated and layout on 1.6mm FR4 substrate. The circuit design is in ISM band, and the frequency is 2.45GHz. According to the measured results, the performance of the fabricated circuit is similar to the simulation one. The rejection frequency derived from the design equation meets the characteristics of the fabricated circuit. It proves that both the theoretical and the simulation results are in good agreement within the frequency of interest.
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