| dc.description.abstract | This dissertation employed three methods to design multi-band bandpass filter: (a) double-layered substrate; (b) asymmetrical resonator and (c) semi-lumped resonator.
(a) Double-layered structure
In the first section, a double-layered structure was proposed to design the multi-band bandpass filter, and explore the use of double-layered structure and stepped-impedance resonators. In the design of double-layered substrate, the useful circuit layout has twice area than the general single-layered substrate provide more design freedom; in the use of stepped-impedance resonator, the fundamental frequency and harmonics can be controlled by the design of the electrical length ratio and impedance ratio. Such design method not only can provide the multi-band bandpass filter design, but also reduce the use of circuit area. In this study, the double-layer structure was used to design the quad-band bandpass filter, quad-band bandpass filter with wide stopband response and quint-band bandpass filter.
(b) Asymmetrical resonator
In the second section, the asymmetrical resonator is composed of three microstrip uniform impedance resonator with different electrical length. By using theoretical analysis, projected herein, may be accurately design asymmetrical center of the resonator frequency and mode of high-frequency wave bands, and then design to achieve the desired passband response. In this study, the use of asymmetrical resonator design tri-band-pass filter, and tri-band pass filter with suppression of a wide stopper.
(c) semi-lumped resonator
In the third section, the semi-lumped resonator was proposed to design multi-band bandpass filter, and it is composed of two microstrip uniform impedance resonator and a lump inductor. Compared with previous general microstrip uniform impedance resonator, the proposed semi-lumped resonator has the characteristic of size reduction and harmonic control by designing the microstrip line and inductance. In this study, the use of the semi-lumped resonator was used to design the distributed sext-band bandpass filter and sharp-rejection sext-band bandpass filter.
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