| Summary: | 碩士 === 國立臺灣科技大學 === 電子工程系 === 91 === The chain-scattering matrices (T matrix) of the z-transform representations are developed for parallel coupled lines. Particularly, the uses of such representations facilitate the investigation of circuits having cascade connections of two or more two-port networks. Furthermore, the z-transform representations of circuit elements make it possible to utilize application tools in digital signal processing (DSP) study. As such, the thesis proposes a novel method to design filters in the microwave frequency. The basic concept is to form the networks by cascading parallel coupled lines, serial and shunt transmission lines of unit electrical length into a new configuration. The transfer function T(z) of the transmission-line network is expressed in the Z domain. It is demonstrated that the zeros of the transfer function T(z) are fully represented by the proper transmission-line elements. In addition, an optimization method is proposed to tune the characteristic impedances of the circuit elements so that frequency response of the transfer function T(z) is close to the system function F(z) of an ideal prototype filter. To validate the proposed approach, two Butterworth band-stop filters, an Elliptic low-pass filter and Chebyshev Type Ⅱ low-pass filter are implemented in the formats of microstrips. The above agreement between experimental results and theoretical values illustrates the validity of this novel method.
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