| 摘要: | 本論文旨在提出可應用於射頻前端之關鍵零組件，。本文首先提出了一個與低溫陶瓷共燒技術結合之微型寬頻濾波器。藉由外加一耦合電容於傳統的二階耦合線段濾波器中間，並產生傳輸零點且具有86%的傳輸頻寬，為了進一步提升外頻的選擇度。本文增加了寬頻濾波器的階數並使用低溫陶瓷共燒技術來實現，該一提出之寬頻濾波器頻段為3.1至5.1 GHz，最後並實現了四個傳輸零點以確保本濾波器的選擇度。接著本文提出了一多頻段濾波器的設計架構，一個典型的二階耦合線段濾波器被分隔成兩個區塊，其中接地端的耦合線段被設計成為階梯式電路，藉由放置適當的電容器於此一階梯式電路，可以達成多頻濾波器的設計，各個頻段之中心頻率可以被自由的調整而不會互相影響，此一多頻濾波器分別以雙頻濾波器(2.4 and 5.5 GHz)與三頻濾波器(2, 4.1, and 7.2 GHz)展示，並亦使用低溫陶瓷共燒技術來實現此一設計概念。此外，本文亦展示可應用於射頻前端電路之平衡器，並提出了平衡器選擇度之技巧。藉由這些技巧，此一平衡器增加了三個傳輸零點，可以有效的來加強外頻的選擇度，所需的公式亦被提出，最後並以低溫陶瓷共燒技術來實現此一平衡器，達到微型化與高性能之目的。更進一步地，本論文更提出了一個適合安裝於無線通訊手持裝置之三頻天線於Wi-Fi (2.4–2.48 and 5.15–5.8 GHz) 與 WiMAX ( 3.3–3.7 GHz ) 應用。為了實現此三頻天線於有限的空見內，兩個L型之單極天線被堆疊於多層印刷電路板，並完成2.4 與 3.5 GHz的輻射功能，進一步再堆疊另一個U型的寄生金屬元件，完成了5.5 GHz頻段之輻射，為了可以達成微型化的目的，除了使用多層印刷電路板製程外，亦使用了兩顆電感來縮短天線的電氣長度同時完成阻抗匹配，此一三頻天線尺寸僅僅為8x8x1.6(mm) ，量測與模擬結果也有良好的一致性，非常適合應用於現代無線通訊裝置之上。This dissertation focuses on the key components of RF front-end systems for various wireless communication application. A new design scheme for the wideband filters with the low temperature co-fired ceramic (LTCC) technology is proposed in this letter. Based on the traditional second-order combline filter, an extra shunt capacitor is added in the middle of the coupled line, and a new transmission zero is thus obtained. The proposed design not only possesses excellent selectivity at both sides of the passband, the fractional bandwidth can also be as wide as 86%. To validate the design scheme, the proposed technique is applied to the third-order ombline filter and realized by using the LTCC technology. The wide-band filter with passband of 3.1–5.1 GHz is obtained. With four transmission-zeros, the selectivity and out-band rejection of the third-order filter is further improved from those of the second-order designs. A systematic design scheme for multi-band filters is proposed based on the conventional single-band combline filter. In the proposed design, the coupled line in the filter is divided into two sections, and one of the sections is replaced with a ladder circuit consisting of parallel capacitors and series coupled lines. The center frequency and fractional bandwidth of each passband can be adjusted without significantly affecting those of the other passbands. The design scheme is illustrated with a dual-band (2.4 and 5.5 GHz) and a tri-band (2, 4.1, and 7.2 GHz) combline filters. Both designs are realized using low-temperature co-fired ceramic technology. Not only the design procedures are given and explained in detail, experimental validation is also conducted. In addition, convenient techniques of selectivity enhancement for lump-distributed baluns are proposed in the paper. With these techniques, transmission zeros are introduced by adding circuit components to the balun. First, novel balun circuits which possess a transmission zero in the differential-mode operation are proposed. A shunt capacitor is then added to the balun to provide a mechanism for tuning the position of the zero. To further improve the frequency selectivity, one more transmission zero which appears in both three-port and differential-mode operations is introduced by adding one transmission line and two capacitors to the balun. Not only equations required for circuit designs are derived, also the proposed circuits are realized by using LTCC process and validated by measurements.Furthermore, this dissertation proposes a triband antenna design for Wi-Fi (2.4–2.48 and 5.15–5.8 GHz) and WiMAX (3.3–3.7 GHz) applications. In order to accommodate the antenna into the limited space, two L-shaped monopoles are stacked on top of each other. These stacked monopoles are used for the radiation in 2.4- and 3.5-GHz bands. Additionally, one parasitic U-shaped strip is placed alongside the stacked monopoles for the radiation in the 5.5-GHz band. Two on-chip inductors are inserted into the monopoles for impedance matching and further miniaturization. The proposed design can be contained in a volume of 8x8x1.6(mm) and built on the printed circuit board. Simulation and measurements are conducted, and both results have proven to be in good agreement. |
