結合數位波束合成技術之單脈衝定向系統

Abstract

本論文是利用單脈衝系統概念，藉由類比數位轉換與訊號處理的方式來獲得來波角度。藉由單脈衝系統的訊號差除以訊號和來確認對應其方位有來波。此系統操作於 925 MHz，天線形式為高增益、高指向性的平面準八木宇田天線，藉由二次降頻將頻率降到基頻，其途中IQ解調器使得訊號相差〖90〗^°，利用類比數位轉換卡將訊號給予電腦。其後端處理數位運算方式是經由論文[1]之架構開放數位式之波束掃描系統。依據實驗結果顯示，本系統即使在複雜的環境中發射低功率，仍然可以即時解出來波方向，且偵測來波的角度極為精確。

In this these, a digital beamforming for directed searching system is implemented. The system contains two way, including Quasi-Yagi antenna, band-pass filter, mixer and IQ demodulator. According to the physical mechanism of the system, the antenna spacing can be obtained by incident wave’s phase difference. The operation frequency of this system is 925 MHz. Besides, the system has dual conversion receivers. The frequency band of first down conversion receivers will be double side band (875 MHz and 975 MHz). What we want is the lower side band, so a band-pass filter is adopted to remove upper side band. And the frequency band of another one is baseband. In order to achieve digital beamforming, a digital signal process is applied.