毫米波頻段放大器及功率放大器之共模穩定性研究

Research of Amplifiers and Common-mode Stability of Power Amplifiers at Millimeter-wave Frequencies

莊博翔(Po-Hsiang Chuang)

指導教授 ： 王暉

國立臺灣大學/電機資訊學院/電信工程學研究所/碩士(2018年)

https://doi.org/10.6342/NTU201900470

摘要

本論文介紹一個製作於砷化鎵假型高速電子場效電晶體製程之低雜訊放大器、一個製作於互補式金屬氧化物半導體製程之開關鍵控調變器，以及一個製作於互補式金屬氧化物半導體製程之功率放大器。
首先為一個應用於第五代行動通訊之Q頻段低雜訊放大器以0.15微米砷化鎵假型高速電子場效電晶體製程設計與製作，此低雜訊放大器採用三級共源級的架構，第一共源級採用源級衰退技術以達到均衡的雜訊及增益表現，而第二、三共源級則是採用RC回授技術以達到寬頻表現，另外，放大器第三級前後之匹配網路採用π型匹配網路以達到寬頻的阻抗匹配。在第一次實驗結果後，電晶體模型不準確導致量測與模擬結果的不一致，在進一步討論與分析後提出模擬上的修正方法，修改晶片設計後再藉由第二次晶片製作及實驗結果驗證所提修正方法之正確性。此低雜訊放大器放大器達到優異的3-dB頻寬(24.7至40.0 GHz)以及平均增益(22.2 dB)表現，雜訊指數則在寬頻(27.9至40.0 GHz)下皆低於3 dB。
之後描述一個應用於短距無線通訊之60-GHz頻段開關鍵控調變器以90奈米互補式金屬氧化物半導體製程設計與製作，此調變器結合了發射機中調變以及輸出放大之功能，進而達到在未來的應用上低複雜度與高效率的發射機架構。此調變器基於共源共柵架構，並採用在此提出的一基於變壓器之回授技術，此技術能提升調變器「開」狀態下的增益及輸出功率表現，以及「關」狀態下的隔離度表現，另外，為了降低基頻調變訊號輸入路徑上的RC常數以減輕高速率傳輸下基頻調變訊號的失真，該路徑透過一串接電感及到地電容的設計以達到所要目的。藉由採用基於變壓器之回授技術，此開關鍵控調變器於60-GHz達到優異的輸出1-dB 功率壓縮點(7.0 dBm)、小訊號增益(10.2 dB)、以及「開-關」隔離度(45.4 dB)表現，在開關鍵控調變上，此調變器能達到10 Gb/s之傳輸速率，由於變壓器所需的低佈局空間優勢，加上僅需單一調變訊號輸入路徑，此調變器達到相當小的晶片佈局。
最後則討論一個應用於短距無線通訊之W頻段功率放大器以65奈米互補式金屬氧化物半導體製程設計與製作，藉由於輸出端採用一基於變壓器之放射對稱功率結構，以達到低損耗及阻抗匹配上的不平衡，此二項參數皆在極高頻的功率放大器設計上有相當大的重要性。在第一次實驗後於毫米波頻段發現非預期的振盪現象，在討論以及多方面的穩定性分析後判斷為共模訊號下位於輸出級的不穩定現象，並提出針對輸出級前後採用的變壓器設計的電路修改方法，在不影響差動訊號下之阻抗匹配情況的前提下，消除共模訊號下之不穩定現象，經過在第二次晶片製作，實驗顯示非預期振盪之問題已解決，並驗證所提出修改方法的正確性。另外，亦討論了用於極高頻功率放大器電路設計時的變壓器模型問題。

關鍵字

砷化鎵假型高速電子場效電晶體 ； 第五代行動通訊 ； 低雜訊放大器 ； 寬頻 ； Q頻段 ； 互補式金屬氧化物半導體 ； 開關鍵控調變 ； 調變器 ； 功率放大器 ； 發射機 ； 共柵共源 ； 變壓器回授 ； 隔離度 ； 60 GHz ； V頻段 ； 功率結合結構 ； 毫米波振盪現象 ； 共源訊號不穩定現象 ； W頻段

並列摘要

The thesis presents a GaAs pHEMT low noise amplifier, a CMOS on-off keying modulator, and a CMOS power amplifier.
Firstly, a Q-band low noise amplifier for fifth-generation communication applications is designed and realized in 0.15-μm GaAs pHEMT. The LNA consists of three common-source stages. Source degeneration is adopted at the first stage for a balanced noise and gain performance, and RC-feedback is adopted at the latter two stages for its wideband characteristics. In addition, π-type matching networks are used at the third stage for wideband impedance matching. Inaccurate device modeling caused disagreement between the measurement and simulation results of the original LNA. The modeling issues are discussed and analyzed, and corrections to the simulation setups are proposed and verified via the measurement results of a modified LNA in the second tape-out. The LNA exhibits wide 3-dB bandwidth from 24.7 to 40.0 GHz, with average gain of 22.2 dB. The noise figure is below 3 dB from 27.9 to 40.0 GHz, with average of 2.6 dB from 26 to 40 GHz.
Secondly, a 60-GHz OOK modulator for short range wireless communications is designed and realized in 90-nm CMOS. By combining the functions of modulation and output amplification in a single circuit, a transmitter of lower complexity and higher efficiency can be achieved for future applications. A novel transformer-feedback technique is proposed for the cascode-based modulator for improvements in output power, gain performances at on-state, and isolation performance at off-state. A data input network is designed to achieve low RC time constant, and avoids distortion of the baseband data signal at high data rates. With the proposed transformer-feedback technique, the modulator achieves an OP1dB of 7.0 dBm, gain of 10.2 dB, and on-off isolation of 45.4 dB at 60 GHz. For OOK modulation, data rates of up to 10 Gb/s have been measured. Due to the compact transformer and the single modulation path required, the modulator achieves a compact layout footprint of 471 x 519 μm2 with RF and DC pads included.
Finally, a W-band power amplifier is designed and realized in 65-nm CMOS. A transformer-based radial-symmetric power combining structure is adopted at the output for low insertion loss and matching imbalances, which are critical in PA designs at such high frequencies. Undesired oscillations at millimeter-wave frequency were observed during measurement of the original PA. Discussions and various stability analyses are performed to identify the issue as common-mode instabilities at the output stage. Modifications to the transformers at the output stage are proposed in order to eliminate the common-mode instabilities, without altering the impedance matching conditions in differential mode. The proposed modifications are verified through the absence of undesired oscillations during the measurement of a modified PA in the second tape-out. Modeling issues of high frequency transformer designs are also discussed.

並列關鍵字

GaAs pHEMT ； fifth-generation (5G) communications ； low noise amplifier ； wideband ； Q-band ； CMOS ； on-off keying (OOK) ； modulator ； power amplifier ； transmitter ； cascode ； transformer feedback ； isolation ； 60 GHz ； V-band ； power combining ； millimeter-wave oscillation ； common-mode instability ； W-band

參考文獻

Reference

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2 T. S. Rappaport et al., “Millimeter-wave mobile communications for 5G cellular: It will work!,” IEEE Access, pp. 335–349, 2013.

3 Y. T. Chou, C. C. Chiong and H. Wang, "A Q-band LNA with 55.7% bandwidth for radio astronomy applications in 0.15-μm GaAs pHEMT process," 2016 IEEE International Symposium on Radio-Frequency Integration Technology (RFIT), Taipei, 2016, pp. 1-3.

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