具有高精準度的23.8 GHz微波輻射計系統設計與量測

Abstract

本論文將實作一個23.8GHz的迪克微波輻射計，此微波輻射計系統具有高精準度用來量測不同水溫。為了準確地控制熱雜訊源與參考雜訊源，此熱控機制用電子冷卻器與風扇組成。為了提高精準度與穩定度，此微波輻射計在迪克開關器後面接上的兩級低雜訊放大器與功率偵測器都使用熱控裝置控溫。系統校正的正確性會影響目標水溫判別的正確與否及精準度的好壞，故校正也是精準度的重要影響因素。此校正系統我們使用冷熱源校正法，但實作此迪克微波輻射計有路徑上的誤差，故需在冷熱校正之前先做路徑差的校正。在本論文最後的實體微波輻射計量測不同水溫結果，呈現出此系統的高精準度。

A 23.8 GHz microwave radiometer system prototype which employs the Dicke architecture for temperature measurement is presented. This radiometer system is used for the evaluation of different water temperature that is read by it with high accuracy. Two low noise amplifiers are used after the radiometer Dicke switches in both the input paths of antenna and reference temperature. In order to control hot and reference sources, a practical temperature control system composed of thermoelectric coolers and fans is utilized. Moreover, by stabilizing the temperature of the two low noise amplifiers and power detector, the accuracy of the radiometer can also been improved. Calibration is important because it affects not only the correctness of the analysis of the received signal but also the accuracy of the system. Here we use hot/cold source calibration which is mostly used in the radiometer. Before this, we also need to calibrate the difference between the input paths of antenna and reference temperature that is caused by the implementation. Some measured results show that this developed radiometer system can read different water temperature with high accuracy.