The Design And Implementation Of The Ionosphere High Frequency Doppler Receiver

Measuring the high frequency Doppler shift of the ionospheric echo is one of the most important methods to study the ionospheric disturbances and irregular structures.We work around this direction and develop a new generation of high frequency Doppler receiver which continuously observes the 10 MHz BPM signal from the short-wave timing station of the National Time Center of Chinese Academy of Sciences and record the data in real time.Through Analyzing and processing the recorded data,experiment detection and result analysis of ionospheric disturbance and irregular body phenomenon is realized on this platform.First,this article systematically introduces the hardware design of the newly developed high-frequency Doppler receiver.The hardware part of the system is composed of a HF programmable receiver with high stability,a high-speed capture card and a PC and an antenna.The system has all the features of the shortwave communication receiver,also has the characteristics of high frequency stability,narrow receiver band,etc.In addition,the system also uses PCIe bus high-speed acquisition system directly to the secondary mixer output IF signal.This method not only reduces the complexity of the system,but also greatly improves the precision of the system,and can obtain higher accuracy of the ionospheric Doppler frequency shift information.Secondly,this paper introduces the software design of high frequency Doppler receiver.The software of the system is divided into analysis and processing display system and real time data acquisition system.Analysis and processing display system is often used in a specific case of offline analysis and real-time data acquisition system is used in the routine observation of the ionosphere.Real-time data acquisition system is programmed by DAQmx,LabVIEW and MATLAB.The system combines the excellent data acquisition capability of DAQmx,the excellent LabVIEW interface programming ability and the excellent mathematical computing power of the MATLAB.The system gives the data collected by the DAQmx to the MATLAB processing and displays it on the front panel of the LabVIEW in real time.The program has a flexible configuration,and the ionospheric Doppler shift can be stored in both text and pictures,which can be used for long time monitoring and recording of the ionosphere.Thirdly,we install the newly developed high-frequency Doppler receiver system in Wuhan area to continuously monitor the BPM signal.By analyzing and processing the measured original signal in the time domain and the frequency domain,the results are in full compliance with the BPM signal characteristics.It shows that the hardware and software design of high frequency Doppler receiver is reasonable,the work of the system is stable and reliable,and the development is successful.Based on the data accumulation and the vertical data of the digital altimetry PDI-2 installed at the same location,some typical events of ionospheric disturbance were found,including the ionospheric diurnal variation,the small and medium scale TID,Large-scale TID and ionospheric irregularities and so on.Finally,using the observation data of high-frequency Doppler receiver,we systematically studied the ionospheric irregularities.The Doppler expression of the ionospheric irregular body motion is deduced.The ionospheric irregular body reflection model is calculated,and the Doppler spectral characteristics of the ionospheric echo are simulated.Combined with the high frequency Doppler reception,the measured data show that the consistency between the two is good.The results show that the Doppler shift curve of Es echo usually appears smooth and straight during the daytime and becomes diffused at night,and sometimes appears straight traces and oblique traces.This phenomenon indicates the drift of irregularities in Es or in the extended F-layer.In summary,this paper systematically introduces the hardware and software design of the newly developed high-frequency Doppler receiver.By using the high frequency acquisition system of PCIe bus technology,the complexity of the system is reduced and the precision of the system is improved.The combination of LabVIEW,MATLAB and DAQmx makes the upper computer more functional.A case study of the ionospheric disturbance in the area of Wuhan was conducted by using measured data.The movement of the ionospheric irregularity was analyzed.Experimental results show that the newly developed high-frequency Doppler receiver is stable and reliable and can be used for long-term continuous monitoring of ionospheric space environment.It is of great significance for observing ionospheric disturbances and ionospheric irregularities.