小型化低溫共燒陶瓷天線前端模組之開發

Abstract

本篇論文旨在利用低溫共燒陶瓷(LTCC)多層架構的基板，設計一嵌入式內含天線的一個小型化5 GHz的射頻前端模組，而且能夠將這個模組用於IEEE 802.11a無線區域網路的應用當中。在這個LTCC模組當中，包含了一個嵌入式的倒F型天線，一個帶通濾波器和一個低通濾波器。而這兩個所提出來的濾波器能在截止的頻帶產生額外的傳輸零點，並且能夠抑制一些不需要的訊號。再者，我們在這個LTCC的基板表面上黏著了一個雙刀雙擲(DPDT)的傳送/接收裸晶片開關切換器，並且利用金屬鎊線的方式將這個裸晶片開關切換器與內埋式的被動元件電路連接起來。所以在我們設計的濾波器當中，必須要把鎊線近似於等效電感的效應考慮和計算進去。整個完成後的LTCC天線射頻前端模組的尺寸大小為6.2 mm × 5.4 mm × 0.98 mm，在整個模組的設計當中，為了使天線有最佳的輻射效能，所以大部份的空間是保留給所設計的天線使用(接近三分之二的空間)。並且，為了避免內埋式的被動電路元件和天線之間產生潛在性的近距離耦合效應，也為了增加元件和天線之間的隔離度，所以在模組的設計上，利用許多的金屬貫穿孔將上層的接地面和下層的接地面互相連結起來。由於小型天線的輻射場型容易受到附近電路接地面所感應出的接地電流所影響，所以我們將所設計出來的天線射頻模組放在兩種不同大小的FR4印刷電路板(PCBs)上面做測試(即55 mm × 20 mm和80 mm × 46 mm兩種不同的印刷電路板)，用來驗證天線射頻模組在這兩個不同大小的PCB上都能夠有不錯的特性。

This thesis proposes a compact 5 GHz front-end module with embedded antenna on a low-temperature co-fire ceramic (LTCC) substrate, which is to be used for the IEEE 802.11a wireless local area network (WLAN) applications. This module comprises an embedded inverted-F antenna, a band-pass filter, and a low-pass filter. Both the proposed filters possess transmission zeros at out band for suppressing unwanted signals. Also, a double-pole double-throw (DPDT) bare die transmitting/receiving (T/R) switch is mounted on the surface of the substrate. The interconnection between the bare die switch and the buried circuits is established by bond wires. The effect of the bond wire is considered by incorporating its equivalent inductance into the design of the filters. The overall size of the antenna front-end module is only 6.2 mm × 5.4 mm × 0.98 mm, with most of the space (near two third of the volume) reserved for the antenna so as to have a better radiation performance. Also, to avoid the potential close proximity coupling among the buried circuits and the antenna, numerous metal vias connecting the top and bottom grounds in the module are designed for shielding. Since the radiation of a small antenna is influenced by the nearby circuit ground due to induced ground current, the developed antenna front-end module is tested on two FR4 printed circuit boards (PCBs) with different sizes (i.e., 55 mm × 20 mm and 80 mm × 46 mm). It is demonstrated that the antenna module performs well on these two grounded PCBs.