94 GHz 被動影像雷達一維成像系統整合

Abstract

本論文提出應用在W-band 之被動影像雷達系統，系統整合各元件:透鏡、高指向性之天線、低雜訊放大器、功率偵測器以及運算放大器，利用不同待測物之天然熱輻射能量差異，來觀察輸出的電壓差，並藉此來分辨物體。為了有效分辨不同天然熱輻射所造成的微小電壓差，進行關鍵元件的量測來確認其特性，包含透鏡效率、天線之場型、低雜訊放大器之增益及其阻抗、功率偵測器之敏感度及其阻抗、運算放大器之增益。確認個別元件的特性後，在天線與後端電路之間設計適當的轉接，讓整體模組因阻抗不匹配而造成的損耗減小。 在整合模組後，利用類比數位轉換器NI PXI-5122來將輸出電壓由類比訊號轉為數位訊號，並透過積分來消除高頻雜訊，觀察輸出電壓變化則利用熱源冷源的量測，並利用此電壓差來確定整體系統之熱敏感度後，進行人體與金屬及空氣的量測並且探討其輸出電壓變化的合理性以及影響效能之關鍵因素。 最後單一路徑之被動影像雷達系統透過機械式移動待測物來進行一維成像，電壓以圖形表示，完成辨別人體與金屬或其他物體之目標。

The thesis introduces to the W-band passive imaging radar system. The system integrates elements, including lens 、an antenna with high directivity、a low-noise amplifier、a power detector and an operation amplifier. By means of the difference of natural thermal radiation power resulted from different objects, we can use the output voltage difference to tell different objects. In order to distinguish the little voltage difference efficiently, we measure key elements to ensure their characteristics., including the efficiency of the lens, antenna patterns, the gain and the impedance of the low noise amplifier, the sensitivity and the impedance of the power detector, the gain of the operation amplifier. According to the characteristics of the elements, we design proper transition between the antenna and the back-end circuits to reduce the loss resulted from impedance mismatch of the module. For the baseband circuits, we use NI PXI-5122 to convert the output voltage from analog signal to digital signal. To avoid the dc signal degradation caused by high frequency noise, we implement signal integration technique to improve the signal quality. Through hot- and cold-source measurement, we can observe output voltage difference, which can be applied to calculate the thermal sensitivity of the whole module. Based on the calculated sensitivity, we can verify the voltages resulted from a human body, coppers and air. In addition, the key points to the system performance are discussed. Finally, the W-band passive imaging radar system with a single channel shows one-dimensional image by mechanical scanning. Therefore, we achieve the goal of distinguishing human bodies and coppers or other objects.