| Summary: | 博士 === 國立臺灣大學 === 電信工程學研究所 === 95 === Pursuit of wider rejection bandwidth, compactness of occupied circuit size, sharpness of frequency selectivity, and broader realizable passband is the controlling idea among the overall dissertation. For this reason, this dissertation principally focuses on three different filter topologies so as to make the stringent requirements possible. The central concept is making good use of dual-metal-plane configuration which provides numerous advantages superior than those of conventional uniplanar approach. In this work, the dual-metal-plane configuration ultimately facilitates the designs of inline coplanar waveguide (CPW) filters with wideband spurious suppression, patch-via-spiral resonators for the development of miniaturized filters, and composite right/left-handed filters with wide fractional-bandwidth.
In the beginning, for the sake of spurious suppression, inline CPW bandpass filters composed of quarter-wavelength stepped-impedance resonators are proposed, using loaded air-bridge enhanced capacitors and broadside-coupled microstrip-to-CPW transition structures for both wide-band spurious suppression and size miniaturization. Three effective spurious suppression mechanisms including spurious destruction, spurious cancellation, and higher order spurious attenuation are incorporated in the proposed CPW filters and thus make the filter stopband extended up to 19.04f0.
Next, to achieve the filter miniaturization and simultaneously provide sharper passband, a novel patch-via-spiral resonator based on the dual-metal-plane configuration is proposed and examined. With the microstrip patch on the top plane serving as a capacitor and linking to the quasi-lumped spiral inductor on the bottom plane through a connecting via, the proposed dual-plane resonator structure located on the opposite sides of single substrate may form a miniaturized one in the printed-circuit board fabrication. By appropriately arranging the proposed patch-via-spiral resonators, useful coupled-resonator pairs may be constructed to provide electric and magnetic couplings along top- and bottom-planes, respectively. Therefore, the two couplings existing between coupled-resonator pair can be made with the same or opposite sign and are first carefully examined in 2nd-order filters with either Chebyshev or quasi-elliptic-like response. Then, the design concept is generally extended to 4th-order filters which possess good frequency selectivity and compact sizes of 0.188λg0 × 0.043λg0, where λg0 stands for the guided wavelength at center frequency.
Finally, in order to realize the filters with wide fractional-bandwidth, composite right/left-handed bandpass filters with wide fractional bandwidth are also implemented based on the proposed dual-metal-plane configuration. With proper design of the symmetric composite right/left-handed unit cell composed of arbitrarily adjustable lumped-elements, the passband, as well as the fractional bandwidth, can be constructed. Specifically, the implemented filters possess relatively achievable wide bandwidth in comparison with the conventional filters based on the assumption of narrow fractional-bandwidth. Besides, the approach for realizing the filters requiring broad bandwidth by cascading multiple CRLH-TL unit cells is found not suitable for filters demanding narrow bandwidth, since the corresponding lumped-element values are not practical in implementation. For this reason, by means of ZORs and inductively-coupled impedance inverters, one may easily design a filter with narrow bandwidth around 10%.
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