本論文提出兩種新式的可調式吸收帶止濾波器設計，能同時具有頻率可調特性與良好的功率消耗效果。本研究藉由在傳統反射式帶止濾波器中加入可變電容，藉此能用電壓控制其電容值而改變傳輸線等效電氣長度與共振頻率，使其具有止帶中心頻率可調之效果，並根據窄頻或寬頻應用，提出兩種設計方式。為了驗證所提出的設計流程，本研究於印刷電路板上實現各電路，在窄頻可調式吸收帶止濾波器設計上，可調頻率範圍為1.95~3.29 GHz，可調度為69%，止帶抑止度為7.621~18.633 dB，3-dB止帶頻寬為7.7~5.2%，功率消耗則從82.687%至98.335%，可看到確實有調頻效果與良好的吸收式止帶特性。而接續並以串接設計使其變為雙頻可調式吸收帶止濾波器，可調頻率範圍分別為2.41~3.88 GHz與3.30~4.89 GHz，其可調度為61%與39%，分別的止帶抑止度為6.759~16.785 dB及6.075~15.010 dB，3-dB止帶頻寬為7.5~5.7%與6.7~5.7%，功率消耗各為78.790%至98.335%與73.494%至95.965%，可看到依然具有功率消耗效果且此兩止帶中心頻率為獨立可調。最後在寬頻可調式吸收帶止濾波器設計方面，實現一頻率可調範圍為520~710 MHz，可調度為37%，止帶中心抑止度為63.893~89.003 dB，其30-dB止帶頻寬為23.9~22.1%，而大於90%之功率消耗頻寬則為35.9~13.5%。本論文提出之兩新型可調式吸收帶止濾波器設計流程簡單，且具有相當高的設計彈性，頻寬、階數、起始頻率選擇與頻率可調範圍，都可隨著系統規格需求而改變，進而快速地設計出可調式吸收帶止濾波器，提升設計效率。;This thesis presents two types of tunable absorptive bandstop filter (TABSF) design, with both a tunable center frequency and a high power dissipation. Specifically, multiple varactors and a resistor are added to the conventional reflective bandstop filter to achieve the proposed tunable absorptive bandstop filter designs. The capacitance of the varator can be controlled by the bias voltage to change the equivalent electrical length and thus the resonance frequency of the transmission line resonators. Therefore, the stopband center frequency becomes tunable. In addition, the resistor provides the proper absorption of the input signal, which turns the reflective bandstop filter into an absorptive one. Two designs are proposed for narrowband or wideband applications. To validate the proposed design methods, test circuits implemented on a printed circuit board are realized, too. For the proposed narrowband tunable absorptive bandstop filter design, the frequency tuning range is 1.95~3.29 GHz (69% tenability). The stopband rejection level is around 7.621~18.633 dB and the 3-dB rejection bandwidth is around 7.7~5.2%.The corresponding power dissipation at the stopband center frequency is around 82.687~98.335%.Next, a dual-band tunable absorptive bandstop filter is realized by the cascade of two proposed narrowband tunable absorptive bandstop filters. The frequency tuning range for the first and second stopbands are 2.41~3.88 GHz (61% tunability) and 3.30~4.89 GHz (39% tunability) respectively. The stopband rejection level is 6.759~16.785 dB for the first stopband while it is 6.075~15.010 dB for the second stopband. The 3-dB rejection bandwidths are 7.5~5.7% and 6.7~5.7% respectively while the power dissipation is 78.790~98.335% and 73.494~95.965% respectively for the first and second stopbands. Finally, the stopband center frequency of the proposed wideband tunable absorptive bandstop filter can be tuned from 520 to 710 MHz (37% tunability). The stopband rejection level is around 63.893~89.003 dB and the 30-dB rejection bandwidth is 23.9~22.1%. The bandwidth for larger than 90% power dissipation is around 35.9~13.5%. The proposed tunable absorptive bandstop filters feature a simple design flow and a high design flexibility. They can be easily designed with the desired stopband center frequency, stopband bandwidth and filter order to meet the system specifications.
