前端接收機研究

Abstract

本論文分為四個部分：第一部份包含了X頻段單端電阻性降頻混波器的設計、模擬、以及量測結果。我們選擇使用單端電阻性混波器的結構來做X頻段的降頻是因為它有低失真以及低雜訊的特性。在這個降頻混波中，RF的頻率為10.9-11.4GHz，LO的頻率為10GHz，而IF的頻率為0.9-1.4GHz。當LO的功率為8dBm，直流偏壓為-0.75V時，變頻損耗皆小於8dBm，而最小值為5.5dBm。 在第二個部分中，我們討論一個兩級的低雜訊放大器。這個低雜訊放大器是用來當作電阻性混波器的前級來使用，他可以放大由天線所輸入的訊號。它在使用的頻段中，有21dB以上的增益，以及低於3dB的雜訊。 在第三部分中，介紹了為混波器所設計的震盪器以及緩衝放大。震盪器主要是產生混波器所使用的LO訊號，而緩衝放大器主要是用來減低由混波器所反射回來的訊號。混波器震盪在9.91GHz，而且有0.83dBm的輸出功率以及-57.83dBm的相位雜訊。而緩衝放大器有大約10dB的增益。 最後我們將低雜訊放大器以及混波器做連結已完成這個前端接收機。

There are four parts in this paper. The first part contains the design, simulation and measurement of an X-band single-ended resistive downconverter mixer. We selected the single-ended resistive mixer structure for X-band downconverter, because it has characteristic of low distortion and low noise. In the downconverter mixer, the RF frequency is 10.9-11.4GHz, LO frequency is 10GHz, and IF frequency is 0.9-1.4GHz. Conversion loss is lower than 8dBm and minimum conversion loss is 5.5dBm which LO power is 10dBm and dc bias is -0.75V. In the second part, we discuss a X-band two-stage low noise amplifier. The low noise amplifier is used ahead of the resistive mixer. It can amplify the single from antenna. The gain of the noise amplifier is larger than 21dB and the noise is lower than 3dB in passband. In the third part, the oscillator and buffer amplifier are designed for the resistive mixer. The oscillator can generate the LO single for mixer and buffer amplifier is used to reduce the reflection from mixer. The power is 0.83dBm at 9.91GHz and the phase noise is -57.83dBm of the oscillator. The gain of buffer amplifier is about 10dB. Finally, the low-noise amplifier integrated with the mixer and antenna to achieve the receiver front-end.