微波頻段主動式循環器與低溫低雜訊放大器之研究及低溫模型之建立

Research of Microwave Active Circulators and Cryogenic Device Modeling for Low Temperature Low-Noise Amplifier

黃鼎傑(Ding-Jie Huang)

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(2013年)

https://doi.org/10.6342/NTU.2013.00483

摘要

此論文包含兩部份，一為互補金氧半導體主動循環器(circulators)的研究，第二部分則是應用於射頻天文接收機的低雜訊放大器設計，及以8-18GHz低雜訊放大器的低溫量測結果所導出的低溫模型。
首先研究24-GHz主動式循環器與訊號相消機制，我們研發一個新的架構並將相消機制的原理用於主動式循環器。在模擬中，半循環器的主要的隔離度|S31|改善了40 dB。此外，本論文也提出三個上述的半循環器而組成的一個全循環器，其中兩個電路皆以0.18-μm 互補金氧半導體技術製作。量測顯示半循環器的注入損耗|S21|及|S32|雖分別為8與9.5 dB，但主要隔離度|S31|可達到30 dB，且所有埠的返回損耗皆大於8.5 dB。而電路的功耗僅9.12 mW且晶片大小為0.34 mm2。全循環器隔離度皆可達50 dB且注入損耗為17 dB，而功耗為36 mW，晶片大小為1 mm2。由這些循環器的表現可得知，訊號相消機制確實可以改善這些電路的隔離度。
論文第二部分論述8-18 GHz低溫低雜訊放大器(cryogenic LNA)的電路設計，並開發假型高電子移動率電晶體(pHEMT)低溫模型。由於電路處於低溫環境，熱散對環境溫度的影響以及電路穩定度與其選定放大器的架構皆須考慮。此外，低雜訊放大器是基於常溫模型所設計，而在低溫進行量測。因電晶體在低溫的表現與常溫不同，致低雜訊放大器在低溫下的表現隨之改變。綜上所述，低溫模型對於設計低溫低雜訊放大器有其必要，藉由溫度分別對假型高電子移動率電晶體及被動元件的影響研究結果，進而提出一個低溫的電晶體模型，且模型內各個參數值則是由前述低雜訊放大器的低溫量測結果所萃取而得。雖然所提出的模型仍較簡略，但可作為之後的低溫低雜訊放大器設計之依據。

關鍵字

微波 ； 循環器 ； 旋轉器 ； 低溫 ； 低雜訊放大器 ； 模型建立

並列摘要

This thesis consists of two parts. The first part is the study of active circulator using CMOS process, and the second part investigates the low noise GaAs pHEMT LNA design for radio astronomy receiver, as well as the cryogenic device modeling based on the cryogenic results of the 8-18 GHz LNA.
We first analyze the 24-GHz active circulators with the signal cancellation mechanism. A novel architecture for the proposed active quasi-circulator with the signal cancellation mechanism is proposed. The main isolation |S31| of the quasi-circulator can be improved to 40 dB in the simulation. Moreover, a full-circulator, which is consisted of three previous quasi-circulators, is also presented. Both of the circuits are implemented in 0.18-μm CMOS technology. The quasi-circulator demonstrates that the insertion losses of |S21| and |S32| are 8 and 9.5 dB, respectively. The measured isolation |S31| of this circulator is 30 dB, and the return losses of all ports are better than 8.5 dB. The power consumption is only 9.12 mW with the chip size of 0.34 mm2. The full-circulator gives the isolation of 50 dB with the insertion loss of 17 dB. The power consumption is 36 mW with the chip size of 1 mm2. These circulators show that the signal cancellation mechanism indeed can improve the isolation of the circuits.
In second part of this thesis, the design of a cryogenic 8-18 GHz LNA and the cryogenic device modeling are studied. The heat disspation, circuit stability, and resulting topologies of the LNA under cryogenic temperature are discussed. The LNA is designed by using the room temperature device model, and then is cooled down for cryogenic testing. The LNA performances at cryogenic temperature are changed since the device behavior changes after being cooled down. Therefore, the cryogenic device model is desired for low temperature LNA design. With the investigation of the temperature effect on HEMT device and passive component, a cryogenic device model is proposed, and the values in the model are extracted by the fitting of the 8-18 GHz LNA measurements. The fitted results of the LNA performances such as the S-parameters and noise temperatures are shown. Though the modeling is simple, the data is valuable for future circuit revision and noise optimization.

並列關鍵字

circulator ； cryogenic ； low-noise amplifier ； low temperature ； device modeling

參考文獻

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