| Summary: | 碩士 === 國立交通大學 === 電信工程系所 === 94 === The thesis includes the two kinds of microwave circuits, namely the miniaturized ultra-broadband quadrature hybrid coupler and the multilayer wideband bandpass filter.
We adopt a 5-section symmetrical cascaded coplanar waveguide (CPW) structure to realize the ultra-broadband (2-18GHz) quadrature hybrid coupler. In the tightest center coupling section, we propose the vertically installed planar (VIP) structure to achieve it and also compensate the unequal odd- and even-mode phase velocities. The fabricated circuit size miniaturized by high dielectric substrate (er=9.8) is 16.8 mm×6 mm.
Then, a wideband (2-4GHz) bandpass filter is designed by using parallel coupled line stepped impedance resonators (SIR). The properties of SIR can reduce the resonant length and suppress the upper stopband interference. Furthermore, we propose multilayer structure to obtain the tight-coupling. Finally, a wideband filter with center frequency at 3 GHz, 66.67% fractional bandwidth, and high stopband rejection is presented.
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