本篇論文主要在於探討36.5 GHz微波輻射接收機的研製，包括射頻前端與類比數位轉換器的實現及量測，並以隨機過程模擬雜訊在經過類比數位轉換器與數位相關器後的結果，有助於了解解析度對於接收機的等效雜訊靈敏度的影響。射頻前端是採用超外插結構設計，將36.5 GHz的射頻訊號降頻至500 MHz的中頻訊號，並提出適當的中頻放大器增益大小，提供全刻度的類比數位轉換器輸入。 在類比數位轉換的實現方面，解析度6位元、取樣頻率1GSPS以及輸入頻寬1.4GHz的快閃式類比數位轉換器的使用，除了滿足本論文的輻射接收機設計需求，更可以提供未來進一步的用途，如直接數位化的處理等。在文中並研究兩種統計模組，針對高斯分佈下的窄頻雜訊擾動來分析，且由電腦程式提供說明，以了解等效雜訊靈敏度與解析度的關係。 從以上系統的實現、量測及模擬，提出了36.5GHz的數位微波總功率輻射接收機之原型機的架構，未來的目標朝著數位相關器的實現與全系統量測以驗證統計模組的結果。 In the thesis,the 36.5 GHz Microwave Total Power Digital Radiometer is designed,implemented and simulated. Include RF front end, analog to digital converter and digital correlator. The superheterodyne structure is applied on the design of receiver frond end. The 36.5 GHz RF signal is then downconverted to 500 MHz IF signal using a mixer-preamplifier. The gain of the IF amplifier are determined in the measurement to achieve the full-scale input of analog-to-digital converter. The flash analog to digital converter digitizes full scale input into 6-bit digital words at an update rate of 1 Giga Sample Per Second (GSPS) . It not only results in the required sensitivity of the radiometer, it also makes the system possibly extended in the future using the direct-sampling approach. Two statistical model of noise signal in digital radiometer are also studied. The narrow band noise signal is modeled as a Gaussian random process. A computer program is developed to help understand the relationship between Noise-Equivalent sensitivity and quantization resolution. Finally the prototype of 36.5 GHz Microwave Total Power Digital Radiometer is presented. Future works will involve realizing the digital correlator to verify the sensitivity predicted by statistical models.
