Cable Phase Difference Detection System And Device Of VHF Antenna Array Based On GPS

Method for measuring VHF antenna array in radio astronomy,in order to antenna pattern and excellent tracking accuracy of different source area,phase measurement technology plays an important role in the process of data transmission.And The phase difference is one of the most important parameters,However,the cable will be affected by many factors such as the natural environment,the cable will produce other unexpected additional phase error.So correcting this error is very important for the optimization of antenna array pattern,But,the complexity and inaccuracy of the traditional measurement methods depend on the characteristics of the phase errors due to the different environmental experiences.According to the principle of VHF antenna array phase measurement,suggesting a better method,which based on GPS(Global Positioning System)synchronization,co-frequency and same phase authorized antenna array for phase difference detection system.The system front end uses AD9910 and GPS as the core chip,programmable DDS(Direct Digital Synthesizer)as the measurement signal,with microwave switch for astronomical signal and error calibration signal selection.Backend mainly uses the phase detection chip AD8302 and cotex-M3 processor comes with low-speed ADC acquisition card as the core chip.It is mainly through the receiver to the antenna between the antenna,through the AD8302 measured cable and calibration cable generated between the phase difference into the corresponding DC voltage,and then 12 bit quantization accuracy of multi-channel ADC sampling.After the data collected by ADC,the error analysis is carried out,and the system error is corrected according to the error analysis result,at last the system measurement error is minimized to meet the measurement accuracy requirement.At the same time the system has two kinds of data acquisition methods,respectively,SD card and directly from the PC side from the serial port to obtain.Taking into account the system usability and versatility,the system provides an interactive interface.The innovation of this paper is as follows:(1)According to the measurement principle of VHF antenna array,this paper proposes the use of GPS cable phase difference detection system,which can effectively avoid the additional errors and measurement complexity of the traditional cable phase difference calibration.(2)By using the GPS as the heartbeat clock,the measurement interface is provided by the interactive interface,and the phase difference detection of the multi antenna array can be eliminated simultaneously.(3)The ARMv7 architecture processor is used to provide a set of measurement system,which includes measurement,error correction and interactive interface.According to the proposed method to make the finished product system,and verified in different frequency measurement conditions through the measured phase error,The accuracy and precision of the phase error of the cable can meet the target of phase difference calibration.(such as the 320 MHz signal input,limit error between the 0cm cable reached ?0.007462cm)The system is especially suitable for the field of digital signal processing method of low frequency antenna array of radio astronomy,and can also be widely used for error correction and error measurement of correlated antenna array.