本論文之雙工器是由一組T型匹配電路連接組合式低通濾波器( Composite low- pass filter )與組合式帶通濾波器( Composite band-pass filter ),使用ADS作為電路與布局之模擬驗證軟體,以及使用MATLAB作為理論分析工具,並利用多層電路板實作驗證,研製一個包含兩個不同頻段並應用於無線網路通訊系統 ( Wireless local area network, WLAN )之雙工器( Diplexer ),組合式低通濾波器是由定K型低通濾波網路(low-pass constant-k section )與導m型低通濾波網路( Low-pass m-derived section )串接,利用導m型低通濾波網路在高頻邊帶頻率產生一個傳輸零點( Transmission zero ),使頻帶4.9GHz到5.95GHz衰減大於43dB,改善頻帶選擇度(selectivity ),定K型低通濾波網路則使衰減隨頻率增加而變大,頻帶7.2GHz到7.5GHz衰減大於30dB,組合式帶通濾波器是由基本高通T型濾波網路( High-pass filter T-section )改良成帶通T型濾波網路( Band-pass filter T-section ),除了有著寬頻的特性,利用鏡像參數法( Image parameter method )分析與參數設計,可在低頻邊帶( Side band )頻率產生一個傳輸零點,抑制2.4GHz到2.5GHz為40dB,達到高選擇度,此帶通T型濾波網路有著類似基本高通T型濾波網路的頻率響應,因此高頻衰減量小,為了使高頻衰減量能夠增加,在帶通T型濾波網路左右兩端接上低通pi型濾波網路,透過傳播常數分析衰減常數與頻率的關係,得到一個符合規格的衰減頻率響應,也就是在頻帶9.8GHz到11.9GHz衰減大於25dB,合成組合式帶通濾波器,最後利用T型傳輸線來匹配,在FR4多層板上實現一個應用於無線網路通訊系統 ( Wireless local area network，WLAN )之雙工器.

In the thesis, we propose the diplexer by using two different bands composite filter configuration with a T-junction microstrip line and fabricated with 4-layered FR4 manufacture. In this study, we use Keysigkt’s ADS to do the circuit and the electromagnetic simulation, and The MathWorks’s MATLAB for the theory formula verification.
In chapter 2, we deal with the composite low-pass filter, the composite low-pass filter consists of the low-pass constant-k filter section and the low-pass m-derived filter section. The transmission zero will provide by low-pass m-derived filter section, the transmission zero frequency could be control by parameter m to achieve band selectivity.
In chapter 3, we will introduce the composite band-pass filter. First, we modify the high-pass filter T-section to band-pass filter T-section by adding two capacitors. One is on the parallel arm and series by the inductor, another is shunt by the inductor. There are two benefits from the capacitors, the series one provides a transmission zero at low frequency from pass-band and reduce interferences from low-frequency side-band; the shunt one provides the broad band band-pass frequency response. This two capacitors aC and bC are the key parameter to the band-pass filter T-section, we will analysis it with image parameter method and verification by MATLAB. We produce a parameter design chart for the parameter a and parameter b. after complete the band-pass filter T-section design, we connect band-pass filter T-section to two low-pass constant-k section for the attenuation requirement, the illustration by the response between attenuation factor and frequency.
Finally, we connect the proposed composite low-pass filter and composite band- pass filter and the T-junction together to implement the diplexer in chapter 4 and illustrate the measure result. Conclusion in chapter 5.

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