X 頻段單閘砷化鎵場效應電晶體主動混波器設計製造與量測

Abstract

本論文是設計，製作，測量一個 X 頻段單閘主動式混波器，本混波器由 一顆砷化鎵製成的場效電晶體所組成。這個混波器的本地振盪信號和射頻 信號被加在閘極，而中頻信號是由汲極所濾出。單閘主動式混波器具有轉 換增益及低雜訊的好處，但是也有本地振盪信號和射頻信號隔離困難的缺 憾。由於頻率的轉換主要來自時變轉移電導，提供本地振盪信號頻率的最 大導抗便很重要。因此，閘極不能有中頻信號和其他混頻信號，汲極上面 也不能有本地震盪信號和諧波，以及各個端口之間的隔離，是這項設計工 作最大的挑戰。我們利用 Libra 的程式做模擬和最佳化。經過不斷的改 良、調整，一個高拒斥的低通濾波器，給偏壓網路應用的抗流元件，以及 輸入匹配電路被設計、製作出來。最後，一個本地振盪信號頻率為 10 GHz、射頻信號頻率為 12 GHz 及中頻信號頻率為 2 GHz 的單閘主動式混 波器的效能被設計、製造、量測，並且得到 5 dB 的轉換增益。 In this thesis, a X-band GaAs MESFET single-gate active mixer was desined, fabricated, and measured. This mixer which the LO and RF signals applied to the gate, and with the IF filtered from the drain. The primarily advantage of single-gate active mixer are conversion gain and low noise figure , but difficult to achieve good LO-to-RF isolation. Because time- varying transconductance is the dominant contributor to frequency conversion, it is important that maximize the fundamental LO- frequency component of the transconductance waveform. Therefore, the gate port can not have IF-frequency and unwanted mixing frequency, the drain port also can not have LO-frequency and harmonics, and provide port-to-port isolation, these problem are need to overcome. We used CAD Libra program to simulation and optimization, a high rejection low-pass filter, choke for bias network, and input matching circuit are designed, fabricated. Finally, a LO frequency is 10 GHz, RF frequency is 12 GHz, and IF frequency is 2 GHz single-gate GaAs MESFET active mixer was designed, fabricated, and measured, we had 5 dB conversion gain.