發(fā)布時(shí)間：2018-03-12 10:13

  本文選題：VHF(Very　切入點(diǎn)：High　出處：《中國(guó)科學(xué)院大學(xué)(中國(guó)科學(xué)院云南天文臺(tái))》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：射電天文觀測(cè)的VHF(Very High frequency甚高頻)天線陣測(cè)量方法中,為了天線方向圖優(yōu)異性和追蹤不同天區(qū)射電源的準(zhǔn)確性,相位測(cè)量技術(shù)在系統(tǒng)數(shù)據(jù)傳輸過(guò)程中起到至關(guān)重要作用。電纜的相位差是其至關(guān)重要參數(shù)之一,然而電纜受到自然環(huán)境等多種因素影響后,電纜還會(huì)產(chǎn)生其他預(yù)想不到的額外相位誤差,修正此誤差對(duì)天線陣優(yōu)化方向圖至關(guān)重要,而傳統(tǒng)測(cè)量方法因其依靠不同環(huán)境經(jīng)驗(yàn)值來(lái)修正相位誤差的特點(diǎn)決定了其復(fù)雜度及不準(zhǔn)確度。根據(jù)VHF天線陣相位測(cè)量原理,提出一種利用GPS(Global Positioning System)同步、同頻、同相位授權(quán)天線陣進(jìn)行電纜相位差檢測(cè)系統(tǒng)。系統(tǒng)前端采用AD9910和GPS為核心芯片,可編程DDS(Direct Digital Synthesizer)作為測(cè)量信號(hào),用微波開(kāi)關(guān)進(jìn)行天文信號(hào)與誤差校準(zhǔn)信號(hào)的選擇。后端主要采用相位檢測(cè)芯片AD8302及cotex-M3處理器自帶的低速ADC采集卡為核心芯片。主要把接收機(jī)至天線陣陣子之間的電纜線,通過(guò)AD8302把測(cè)量電纜和定標(biāo)電纜之間產(chǎn)生的相位差轉(zhuǎn)化為對(duì)應(yīng)的直流電壓,再用12bit量化精度的多通道ADC采樣。經(jīng)過(guò)ADC收集到的數(shù)據(jù),對(duì)其進(jìn)行誤差分析后,根據(jù)誤差分析結(jié)果對(duì)系統(tǒng)進(jìn)行誤差修正,使系統(tǒng)測(cè)量誤差降到最低,以滿足測(cè)量精度需求。同時(shí)系統(tǒng)具有兩種數(shù)據(jù)獲取方式,分別為SD卡和直接從PC端從串口獲取�？紤]到系統(tǒng)實(shí)用性和通用性,為該系統(tǒng)提供了交互界面。本文的創(chuàng)新點(diǎn)主要有:1)根據(jù)VHF天線陣的測(cè)量原理,提出的利用GPS的電纜相位差檢測(cè)系統(tǒng),可以有效避免傳統(tǒng)電纜相位差校準(zhǔn)帶來(lái)的額外誤差和測(cè)量復(fù)雜度。2)利用GPS作為心跳時(shí)鐘,由交互界面提供測(cè)量校準(zhǔn)間隔,同步同時(shí)進(jìn)行多天線陣的電纜相位差檢測(cè),可以有效消除非相干信號(hào)時(shí)的誤差。3)利用ARMv7架構(gòu)處理器提供了一整套包括測(cè)量、誤差修正、交互界面的測(cè)量系統(tǒng),可有效運(yùn)用于天線陣電纜相位差校準(zhǔn)。根據(jù)提出方法做出成品系統(tǒng),并通過(guò)實(shí)測(cè)驗(yàn)證在不同頻率測(cè)量條件下,系統(tǒng)所給出的電纜相位誤差的精度(如300MHz信號(hào)輸入下,0cm電纜之間極限誤差達(dá)到了±0.012cm精度),精度完全滿足天線陣相位差校準(zhǔn)的目標(biāo)。該系統(tǒng)尤其適用于射電天文低頻天線陣的數(shù)字信號(hào)處理方法技術(shù)領(lǐng)域,同時(shí)也可以廣泛用于相關(guān)天線陣誤差修正及電纜誤差測(cè)量。
[Abstract]:In the VHF(Very High frequency very high frequency (VHF) antenna array measurement method for radio astronomical observations, in order to improve the antenna pattern and track the accuracy of radio sources in different sky areas, The phase measurement technology plays an important role in the data transmission of the system. The phase difference of the cable is one of its most important parameters. However, the cable is affected by many factors, such as natural environment, etc. The cable also produces other unexpected additional phase errors, which are critical to the optimization of the antenna array. However, the complexity and inaccuracy of traditional measurement methods depend on the experience of different environments to correct the phase error. According to the principle of phase measurement of VHF antenna array, a new method is proposed to synchronize and synchronize the phase error by using GPS(Global Positioning system. The system uses AD9910 and GPS as the core chip and DDS(Direct Digital synthesizer as the measuring signal in the front end of the system. The microwave switch is used to select the astronomical signal and the error calibration signal. The phase detection chip AD8302 and the low-speed ADC data acquisition card with the cotex-M3 processor are used as the core chip at the back end. The cable line between the receiver and the antenna array is mainly used. The phase difference between the measuring cable and the calibrated cable is transformed into the corresponding DC voltage by AD8302, and then the multi-channel ADC sampling with 12bit quantization accuracy is used. After the data collected by ADC, the error is analyzed. According to the result of error analysis, the error of the system is corrected, so that the measurement error of the system is reduced to the minimum, so as to meet the requirement of measurement accuracy. At the same time, the system has two kinds of data acquisition methods. The SD card is obtained from the serial port directly from the PC. Considering the practicability and versatility of the system, the interactive interface is provided for the system. The main innovation of this paper is: 1) according to the measurement principle of the VHF antenna array, The proposed cable phase difference detection system using GPS can effectively avoid the extra error and measurement complexity caused by traditional cable phase difference calibration. 2) using GPS as the heartbeat clock, the measuring calibration interval can be provided by the interactive interface. Synchronous detection of cable phase difference of multi-antenna array can effectively eliminate the error when incoherent signal. 3) using ARMv7 architecture processor to provide a set of measurement system including measurement, error correction, interactive interface. It can be used to calibrate the phase difference of antenna array cable effectively. According to the proposed method, the finished product system is made, and it is verified by actual measurement under different frequency measurement conditions. The accuracy of the cable phase error given by the system (for example, the limit error between 0 cm and 0 cm under the input of 300MHz signal has reached 鹵0.012 cm precision), and the precision fully meets the objective of phase difference calibration of antenna array. This system is especially suitable for low radio astronomy. The Digital signal processing Technology of Frequency Antenna Array, At the same time, it can also be widely used in error correction of related antenna array and cable error measurement.
【學(xué)位授予單位】：中國(guó)科學(xué)院大學(xué)(中國(guó)科學(xué)院云南天文臺(tái))
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：P161

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