本篇論文將會討論X-band全偏極化散射儀，尤其針對發射與接收模組的設計與研製。由於在X-band頻率中，電磁波在同軸電線裡傳播會造成訊號大量的衰減，故在此使用超外差結構來設計發射與接收端。 本系統是利用向量網路分析儀來作為訊號的來源，因為向量網路分析儀具有很好的訊號處理能力，例如系統的校準及時域的gating均可以輕易地來達成。向量網路分析儀產生的訊號是為1~2GHz，經過混波器後昇頻到9~10GHz，接著使用功率放大器來補償訊號的損失，並提昇散射儀的動態範圍以及量測的靈敏度。本系統是使用單一天線雙模態的金字塔型的號角天線，並加以連接循環器，來避免因使用多重天線而造成天線間的互相干擾。如此一來可以實現量測短距離的回波散射。再加上用電腦控制程式來切換系統的偏極化狀態以及資料的取得，如此可達到自動化全偏極化量測系統的建立。 In this thesis, the transmitter/receiver of a X-band fully polarimetric scatterometer is designed and implemented. Due to the high attenuation of the electromagnetic waves in the coaxial cables at X-band, the superheterodyne structure is applied on the design of transmitter/receiver. A vector network analyzer (VNA) is used as the signal source. Due to VNA's high ability in signal process, many features such as system calibration and time gating can be easily implemented and performed. The signal from the VNA, which ranges from 1 GHz to 2 GHz, is upconverted to 9 GHz to 10 GHz by mixers. An Amplifier is used to compensate the signal attenuation and thus raise the dynamic range and measurement sensitivity of the scatterometer. A computer-controlled switching system is implemented to alternate different polarization states, so the fully polarization measurement can be achieved. An single dual-mode pyramidal horn in conjunction with circulators is applied to avoid the antenna interference inherent in the multi-antenna system. Therefore the backscatter can be measured in short ranges. In order to conduct automatic measurements, a computer program is developed for data acquisition, switching control, and system calibration.
