60-GHz 混波器、正交調變器和單刀雙擲切換器之研製

Abstract

本論文主要是討論吉爾伯特單元降頻混波器、使用複合式左右手傳輸線改善邊帶抑制的調變器以及分佈式單刀雙擲切換器。主要研究方向為發展微波系統內頻率轉換之混波器、正交調變器，以及改進正交調變器內結合正交信號之耦合器；還有發展寬頻切換器使之應用於60 GHz之高頻範圍。 本論文首先討論並研製一60 GHz之吉爾伯特單元降頻混波器；調變器為發送機之重要元件，近年來文獻發表的60 GHz、70 GHz頻段附近的CMOS調變器中，多強調其寬頻的特性；使用QPSK之調變器，必須使用90°耦合器以產生90°的相位差，但傳統之寬邊耦合器較難在極寬頻的範圍內提供耦合端和直接輸出端之間準確的90°相位差和平衡的振幅，因此這些調變器通常無法在很寬頻的範圍內都能達到很高的邊帶抑制，若利用複合式左右手傳輸線之相位領先特性製作一寬頻之正交功率結合器/分離器，則可大幅改善傳統調變器邊帶抑制不佳之問題。最後，單刀雙擲切換器被視為收發機裡重要的切換元件，使用mHEMT製程之分佈式單刀雙擲切換器，能在60 GHz時達到只有2 dB之插入損耗，減少收發機中因切換器帶來之插入損耗而增加的雜訊，應用性極佳。為了得到低插入損耗的特性，單刀雙擲切換器中兩路單刀單擲切換器只各使用了3顆電晶體，因此其隔離度中等(23 – 30dB)。

This thesis discusses Gilbert-cell down-conversion mixer, broadband I-Q modulator with improved sideband suppression, and a distributed single-pole-double-throw switch. The main purpose is to explore the frequency conversion components such as mixer and I-Q modulator, and improve the performance of quadrature coupler used in I-Q modulator to combine two orthogonal signals, and develop a broadband switch for high-frequency application at 60 GHz. In this thesis, a 60-GHz down-conversion Gilbert-cell mixer is discussed and fabricated. Modulators are important components in transmitters, recently reported modulators around 60 or 70 GHz normally emphasize their broadband property. 90° couplers are needed to modulate baseband signals with QPSK modulation. However, it is not easy for conventional broadside coupler to provide balanced output amplitude and accurate 90° output phase split in a very broadband fasion. Therefore, these modulators normally achieve high sideband suppression only in norrowband ranges. Making use of the phase lead property of a composite left/right hand transmission line, broadband quadrature power splitter can be designed. It can improve the sideband suppression of conventional modulators. Finally, single-pole-double-throw switches are important switching components in transceivers. A distributed SPDT switch using mHEMT process is fabricated. The insertion loss at 60 GHz is only 2 dB, which reduces the noise introduced by the switches in transceivers. To obtain low insertion loss, the SPDT switch use only three transistors for each SPST switch branch. As a trade-off from low insertion loss, the isolation is moderate.