基于GPS的VHF天线阵电缆相位差检测系统及装置

发布时间：2018-03-12 10:13

本文选题：VHF(Very　切入点：High　出处：《中国科学院大学(中国科学院云南天文台)》2017年硕士论文　论文类型：学位论文

【摘要】：射电天文观测的VHF(Very High frequency甚高频)天线阵测量方法中,为了天线方向图优异性和追踪不同天区射电源的准确性,相位测量技术在系统数据传输过程中起到至关重要作用。电缆的相位差是其至关重要参数之一,然而电缆受到自然环境等多种因素影响后,电缆还会产生其他预想不到的额外相位误差,修正此误差对天线阵优化方向图至关重要,而传统测量方法因其依靠不同环境经验值来修正相位误差的特点决定了其复杂度及不准确度。根据VHF天线阵相位测量原理,提出一种利用GPS(Global Positioning System)同步、同频、同相位授权天线阵进行电缆相位差检测系统。系统前端采用AD9910和GPS为核心芯片,可编程DDS(Direct Digital Synthesizer)作为测量信号,用微波开关进行天文信号与误差校准信号的选择。后端主要采用相位检测芯片AD8302及cotex-M3处理器自带的低速ADC采集卡为核心芯片。主要把接收机至天线阵阵子之间的电缆线,通过AD8302把测量电缆和定标电缆之间产生的相位差转化为对应的直流电压,再用12bit量化精度的多通道ADC采样。经过ADC收集到的数据,对其进行误差分析后,根据误差分析结果对系统进行误差修正,使系统测量误差降到最低,以满足测量精度需求。同时系统具有两种数据获取方式,分别为SD卡和直接从PC端从串口获取。考虑到系统实用性和通用性,为该系统提供了交互界面。本文的创新点主要有:1)根据VHF天线阵的测量原理,提出的利用GPS的电缆相位差检测系统,可以有效避免传统电缆相位差校准带来的额外误差和测量复杂度。2)利用GPS作为心跳时钟,由交互界面提供测量校准间隔,同步同时进行多天线阵的电缆相位差检测,可以有效消除非相干信号时的误差。3)利用ARMv7架构处理器提供了一整套包括测量、误差修正、交互界面的测量系统,可有效运用于天线阵电缆相位差校准。根据提出方法做出成品系统,并通过实测验证在不同频率测量条件下,系统所给出的电缆相位误差的精度(如300MHz信号输入下,0cm电缆之间极限误差达到了±0.012cm精度),精度完全满足天线阵相位差校准的目标。该系统尤其适用于射电天文低频天线阵的数字信号处理方法技术领域,同时也可以广泛用于相关天线阵误差修正及电缆误差测量。
[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 卤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.
【学位授予单位】：中国科学院大学(中国科学院云南天文台)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P161

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