- 作者: 朱延祥
- 作者服務機構: 國立中央大學太空科學研究所
- 中文摘要: 對大部份的VHF雷達而言,在所接收到的回波信號中無可避免的會受到地面回波的干擾而影響回波信號的品質。欲自雷達回波中分辨出地面回波,可利用傳統的分辨法,如統計法、相位變化法、多重頻率法、回波功率與都普勒頻寬法等來進行。然而不管使用何種方法,均無法自回波信號中將地面回波信號與來自大氣薄穩定層之反射回波信號分辨出。在本研究中將提出所謂的逆極化法來分辨此兩種回波信號。本研究所使用的資料為秘魯JicamarcaVHF雷達觀測所得之圓形極化回波信號,經分析回波之逆極化特性及統計行為,將可精確的定出產生地面回波目標物的位置。此外在本研究中亦將針對由對流層頂所產生的回波作統計分析,以研究其回波機制,結果發現對流層頂似乎是由非同相亂流不規則體所構成,而非由薄穩定層所組成。
- 英文摘要: For most MST radars, the received radar echo signals are inevitably contaminated by ground clutter.Several methods have been proposed to discriminate ground clutter from radar returns, for example, thestatistical method, phase variational method, multiple frequency method, echo power versus Dopplerspectral width method, and so on. However, no matter which method is employed, it is very difficult toseparate ground clutter and echo signals reflected from a thin atmospheric stable layer. In this study, thedepolarization method is proposed to separate these two signals. The data used in this study are thecircular polarized echoes observed by the Jicamarca VHF radar in Peru. After analyzing the depolarizationproperties and the statistical behaviors of the radar returns, the source of the ground clutter canbe identified precisely. The echo mechanism of the atmospheric signals generated from the tropopause isalso investigated. It suggests that the tropopause is composed of anisotropic turbulent irregularities, ratherthan thin stable layers.
- 中文關鍵字: VHF radar; circular polarization; ground clutter; stable layer; depolarization
- 英文關鍵字: --