發展軟體演算實現線性調頻連續波雷達測距系統之設計; Development of the Software Algorithms to Design the Range-Finding System based on Linear Frequency-Modulated Continuous-Wave Radar

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题名:	發展軟體演算實現線性調頻連續波雷達測距系統之設計;Development of the Software Algorithms to Design the Range-Finding System based on Linear Frequency-Modulated Continuous-Wave Radar
作者:	葉宗翰;Yen,Zong-hen
贡献者:	通訊工程學系在職專班
关键词:	線性調頻連續波雷達;差頻;測距系統;訊號補償;LFMCW;beat frequency;range-finding system;signal compensation
日期:	2013-07-30
上传时间:	2013-08-22 12:07:10 (UTC+8)
出版者:	國立中央大學
摘要:	線性調頻連續波雷達以低截獲率、高距離解析度、較無距離盲區及結構簡單等優勢，近年來廣泛受到關注，本研究係以某研發團隊設計開發階段之高度感測器雷達模組雛形架構為研究背景，設計軟體演算法用以解算離地高度之回波差頻訊號，進而實現測距系統之設計。　　首先詳細介紹調頻連續波雷達系統工作原理與結構，並闡述如何對三角波調頻訊號進行分析，進而解算出距離參數，同時根據理論基礎及實際用途相結合，將開發階段的高度感測器，訊號處理無法順利解算出近端目標(地面)訊號的問題，作為研究主軸，藉高杆距離偵測實驗，實際蒐集相關目標回波資料，分別從頻域及時域對調變波訊號進行探究。　　由於線性調頻連續波雷達系統，本身架構存在發射端訊號洩漏問題，加上高度感測器載具硬體製作空間有限，難以有效實現收發之間隔離度，由量測結果發現，回波差頻訊號會因目標距離越遠，訊號強度會逐漸變小甚至遠低於近場雜訊準位，這代表著高度感測器系統降落接近地面時，會無法正確解算目標高度，造成距離偵測能力下降。　　針對實體系統改善方面，研發團隊著手開發出洩漏波陣列雙天線，增加收發端之間的隔離度，本研究則針對近場雜訊及目標訊號強度產生衰減及遭遇干擾之問題，引據迴旋積分、視窗函數、FFT以及地面目標之雷達接收功率損耗與距離平方之特性，以軟體演算建構訊號補償方式，模擬結果證明設計方案有效，除改善雜訊外，同時增強訊號強度，獲得正確訊息且誤差低，符合測距精度可接受範圍，促使整體系統運用層面更為提升。 Linear Frequency-modulated Continuous-wave (LFMCW) Radar has been widely applied in recent years for its advantages of low Probability of Interception, high range resolution, no blind range, and its simple structure. On the basis of the preliminary development of a height sensor Radar model designed by one research team, this paper aims to construct a method of using software algorithms to resolve the beat frequency signal from the relative altitude of the reflected target wave, and further, to implement the design of the range-finding system. Firstly, the paper introduces the work theory and the structure of FMCW Radar, elaborates on the analysis of the triangular wave FM signal, and then calculates the distance parameter. Furthermore, combining both theoretical and practical uses, the paper puts its emphasis on the problem of the height sensor not successfully calculating the proximal target (ground) signal. Through high distance detection experiments, the relevant data is gathered from the target echo, respectively in frequency domain and time domain. Due to the problems of the LFMCW Radar structure, including transmitter signal leakage and limited hardware space of height sensor, it is hard to put the transmit-receive isolation into proper effect. The result of the measurements shows that the farther the target is positioned, the weaker the strength of the signal gradually becomes, even much lower than the near-field noise. This represents that when the height sensor system is close to the ground, it fails to resolve the altitude of the target correctly and undermines its ranging ability. For the height sensor system improvement, the research team had developed a structure of Leaky-wave antenna array pairs, which increase the isolation between the transmitting and receiving antenna. This paper applies convolution, windows functions, FFT, and the characteristics of the square of the distance and ground targets with radar receiver power consumption to encounter the problems of signal attenuation. We establish the signal compensation by software algorithms and the simulation proves the design is valid. It not only reduces the near-field noise but also reinforces the strength of the target signal. The data is correct and the error is low. This design elevates the range-finding system to a higher level by refining the ranging accuracy.
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