應用於微波電路之轉折差動傳輸線與分散式變壓器設計

The Application of Microwave Circuit on Bent Differential Transmission Line and Distributed Active Transformer Design

高鵬(KAO,PENG)

指導教授 ： 吳建華

國立中正大學/工學院/電機工程學系/碩士(2015年)

摘要

本論文研究主軸分為兩部分，為新式轉折差動傳輸線之訊號完整性分析及分散式主動變壓器負載之X頻段功率放大器設計與量測，分別以TSMC 0.18μm製程及FR4板材實現。
新式轉折差動傳輸線的研究重點在於轉折效應的信號完整性分析與改善，本節歸納信號完整性分析的三個面向，混和訊號散射參數分析、共模雜訊電壓時域分析及眼圖時域分析。新式轉折差動傳輸線設計，一方面以弓形轉角取代90度轉角，二方面將內側線寬縮減對訊號產生阻力造成電荷堆積產生相位延遲，並以可調式線段控制相位補償量，使轉折差動傳輸線補償更有彈性。本論文以90度轉折差動傳輸線為比較標準，所提出新架構在頻段0~8GHz內改善模態轉換雜訊4.6~11.4dB不等；當輸入差動電壓訊號振幅為±1V上升時間為100psec，改善共模雜訊電壓達(0.51-0.15)/0.51=70.1 %；當輸入資料量為3Gbits/s且上升時間為100psec的差動訊號，眼高(Eye height)及最大抖動(Jitter PP)分別改善8%及40%。
X頻段功率放大器研究重點一在於輸出功率極大化，透過直流及交流分析探討該頻段電晶體尺寸的選擇，以負載拉移找出最佳化的負載阻抗，接著以分散式主動變壓器結構整合多組推挽式差動放大器，達到阻抗匹配及功率結合網路，轉換效率達88%。重點二在於大訊號下，電晶體偏壓選擇及佈局考量，確保電晶體能正確的放大功率，避免電壓過大擊穿電晶體或因電流過大燒毀走線。
晶片一為單級功率放大器，採用N=8分散式主動變壓器負載結構，電磁分析模擬結果，頻段9.8~14.8GHz的輸入反射損耗大於10dB，頻段9.9~14.2GHz的輸出反射損耗大於8dB，線性增益約為6dB，在1dB增益壓縮點的輸出功率為24dBm、PAE為17.5%，最大輸出功率、汲級效率及PAE分別為28.6dBm、40%及21%，整體消耗功率為1488mW。
晶片二為雙級功率放大器，以主動式巴倫器作為增益級，提供增益並提供180度相位差，功率級採用N=4分散式主動變壓器負載結構，經過電磁分析模擬結果，頻段10.2~12.1GHz的輸入反射損耗大於10dB，頻段9.8~16.1GHz的輸出反射損耗大於8dB，線性增益約為11.8dB，在1dB增益壓縮點的輸出功率為14.8dBm、PAE為3%，最大輸出功率及PAE分別為19.2dBm，整體消耗功率為1401mW。

關鍵字

功率放大器 ； 信號完整性 ； 分散式主動變壓器 ； 轉折差動傳輸線

並列摘要

This thesis includes two topics: one is the novel bent structure design of differential line for noise reduction and signal integrity; another is the design of distributed active transformer loaded x-band power amplifier, which are implemented by pcb fr4 substrate and tsmc 0.18μm process respectively.
The study point of the novel bent structure shown on chapter 2 is to analyze and improve signal integrity of the bent structure effect. On the chapter 2, the analyses of signal integrity are summarizes into three orientations including frequency domain mixed-mode scattering parameter, time domain common-mode noise voltage and eye diagram analysis. The novel bent structure design of differential line adopts arched bend substituting right-angle bend, on the other hand, reducing inner line width to generate obstruction and accumulate electric charge results in phase delay. Moreover, the adjustable line segment can control quantity of phase compensation making compensation of bent structure more flexible. With right-angel bent structure as a standard, proposed bent structure improves mode conversion noise 4.6~11.4dB differing from frequency range 0~8 GHz; In the case of input differential signal with amplitude ±1V and rise time 100psec, proposed bent structure improves common mode noise voltage 70.1%; In the case of input differential signal with Bite rate 3Gbits/s and rise time 100psec, proposed bent structure improves eye width and peak jitter 8% and 40% respectively.
The study point of distributed active transformer loaded x-band power amplifier shown on chapter 4 is to maximize output power. Through DC, AC analysis and impedance pulling, we probe into the amplify ability of different transistor size, furthermore, select total channel width 960μm for the amplifier cell and cascode two amplifier cell as a power cell. Then, apply distributed active transformer to connect with all power cells attaining to power combination and impedance transformation. The second point of the chapter is to make sure the power cell can correctly operate under large signal.
First chip adopting N=8 distributed active transformer structure is one stage amplifier. Momentum EM simulation results indicate that input return loss is larger than 10 dB between 9.8 to 14.8 GHz, and output return loss is larger than 8dB between 9.9 to 14.2 GHz. Linear gain is 6dB. At the 1-dB compression point, output power and PAE are 24 dBm and 17.5% respectively. The maximum output power, drain efficiency and PAE are 28.6 dBm, 40% and 21% respectively. Total power dissipation is 1488mW.
Second chip adopting N=4 distributed active transformer structure is two stage amplifier. Apply active balun to gain stage supplying gain and two opposite signals. Momentum EM simulation results indicate that input return loss is larger than 10 dB between 10.2 to 12.1 GHz, and output return loss is larger than 8dB between 9.8 to 16.1 GHz. Linear gain is 11.8dB. At the 1-dB compression point, output power and PAE are 14.8 dBm and 3% respectively. The maximum output power and PAE are 19.2 dBm and 4.5% respectively. Total power dissipation is 1401mW.

並列關鍵字

Distributed active transformer ； Signal integrity ； Bent structure of differential transmission line ； power amplifier

參考文獻

[6] S. C. Cripps, RF Power Amplifier for Wireless Communications, 1999.

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