本文選題：GPS + 恒溫晶振頻率校準��； 參考：《中南民族大學》2015年碩士論文

【摘要】：隨著信息交換的加快,頻率源的重要性日益突顯。頻率源的不穩(wěn)定會導致同步精度不夠,嚴重情況下還可能造成系統(tǒng)癱瘓。目前精度較高的頻率源是恒溫晶振,但因其存在長期累積誤差,使其難以在同步系統(tǒng)中得到應用。美國的全球定位系統(tǒng)(GPS)搭載了高穩(wěn)原子鐘,其輸出的秒脈沖1PPS信號具有短期穩(wěn)定性好的特點。因此,本文采用GPS秒信號校準恒溫晶振以得到高精度頻率源(稱為GPS頻率校準系統(tǒng))。GPS頻率校準系統(tǒng)是以FPGA數(shù)字技術作為測量手段,ARM處理器作為算法控制中心,采用鎖相環(huán)頻率合成技術,對晶振分頻秒信號和GPS秒信號的相位進行跟蹤鎖定,依據(jù)兩者的相位差變化量調(diào)整頻率修正電壓,在不破壞晶振短穩(wěn)特性的基礎上改善其頻率的長期穩(wěn)定性,以獲取高穩(wěn)定度、高可靠性的頻率源。該系統(tǒng)由GPS信號接收機,高精度數(shù)字鑒相器,數(shù)據(jù)濾波和系統(tǒng)控制,以及晶體振蕩控制等四大模塊組成。其中,GPS信號接收機模塊主要功能是通過放置在室外的專用接收天線接收來自GPS的秒信號1PPS;高精度數(shù)字鑒相器模塊采用數(shù)字測量技術,以高速時鐘計數(shù)的方法實現(xiàn)相位差的高分辨率測量;數(shù)據(jù)濾波和系統(tǒng)控制模塊以誤差分析和平滑控制作為設計思路,在微處理器中實現(xiàn)滑動平均濾波算法和自適應PID控制算法;晶體振蕩控制模塊采用電磁兼容性良好的低噪聲DA控制電路,將處理器輸出的若干比特數(shù)字量在DA電路中轉(zhuǎn)化為高精度的控制電壓。所研制的GPS頻率校準系統(tǒng)在本實驗室中通過長時間觀測表明:晶振分頻秒信號和GPS秒信號的相位差波動范圍不超過65ns,實現(xiàn)了較好的鎖相調(diào)節(jié),且經(jīng)校準后的頻率精度達到了10-10量級。該系統(tǒng)也應用于本實驗室自主研發(fā)的數(shù)字測高儀PDI-1中,成功地進行了兩臺儀器的斜測實驗,很好地滿足了斜測所需要的時間同步要求。
[Abstract]:With the acceleration of information exchange, the importance of frequency sources is becoming more and more important. The instability of the frequency source may lead to insufficient synchronization accuracy and system paralysis in serious cases. At present, the frequency source with high precision is the constant temperature crystal oscillator, but it is difficult to be applied in the synchronous system because of its long-term cumulative error. The Global Positioning system (GPS) of the United States is equipped with a high-stability atomic clock, and the output second pulse 1PPS signal is characterized by good short-term stability. Therefore, in this paper, the GPS second signal is used to calibrate the constant temperature crystal oscillator to obtain the high precision frequency source (called GPS frequency calibration system). The FPGA digital technology is used as the measuring means and arm processor is used as the algorithm control center. Using phase-locked loop frequency synthesis technology, the phase of the crystal oscillator frequency division second signal and the GPS second signal is tracked and locked, and the frequency correction voltage is adjusted according to the variation of the phase difference between the crystal oscillator and the GPS second signal. In order to obtain high stability and high reliability, the long-term stability of crystal oscillator is improved on the basis of not destroying the short-time stability of crystal oscillator. The system consists of four modules: GPS signal receiver, high precision digital phase detector, data filtering and system control, and crystal oscillation control. The main function of GPS signal receiver module is to receive 1PPS signal from GPS through special receiving antenna placed outdoors, and the high precision digital phase detector module adopts digital measurement technology. The high resolution measurement of phase difference is realized by the method of high speed clock counting, the data filter and system control module take error analysis and smooth control as the design idea, the sliding average filter algorithm and the adaptive PID control algorithm are realized in the microprocessor. A low noise DA control circuit with good electromagnetic compatibility is used in the crystal oscillation control module. Some bits of digital output of the processor are converted into high precision control voltage in DA circuit. The developed GPS frequency calibration system has been observed in our laboratory for a long time. It is shown that the phase difference between the crystal oscillator frequency division second signal and the GPS second signal fluctuates in a range of less than 65ns, and the phase locking adjustment is achieved. After calibration, the frequency accuracy reaches 10-10 orders of magnitude. The system is also applied to the digital altimeter PDI-1, which has been developed by our laboratory, and has successfully carried out the oblique test of two instruments, which meets the requirements of time synchronization for oblique measurement.
【學位授予單位】：中南民族大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：P228.4
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本文編號：1821324