Design And Implement Of Signal And Data Processing Subsystem In Wuhan Ionospheric Sounding System

There are many kinds of ionospheric sounding techniques, such as the bottom vertical sounding, the bottom oblique sounding, the bottom oblique backscattering sounding, the topside sounding by the deep space vehicle and the penetrating sounding between ground and space. These techniques can provide the information of the ionosphere, status of ocean and parameters of HF radio channel. These can be used to understand the ionospheric state, physical process, feature as well as the radio wave propagating rule in the ionosphere, reveal the regional features of the ionospheric dynamics and morphology and the ionospheric channel features, improve the reliability and accuracy for describing and forecasting the ionospheric state and the radio wave propagation.The Ionosphere Lab of Wuhan University began to develop the IOBSS for ionospheric research and HF channel management. After the development of almost 10 years, The Ionosphere Lab of Wuhan University has developed a variety of different lonospheric sounding systems, which are collectively called Wuhan lonospheric Sounding System (WISS). WISS is able to cover the range up to 1500km by only 150W peak power, and obtain the transmission feature of HF channel, for example decline, multipath, Doppler, echo’s phase, maximum usable frequency (MUF) and so on. On the platform of WISS hardware, several aspects related to WISS data and signal processing is discussed in this paper, such as development of WISS software platform, working state control of system, generation of sounding data, extraction of echo’s information, sounding information mining, etc. The details of these researches are introduced as follows.1. The research and development of WISS display control and process integrated software platform.WISS software platform adopt OOA and OOD techniques to analyze and design, which makes the developing progress can be iterative and incremental and a lot of needs analysis and design results can be reused. The developing progress is described by Unified Modeling Language (UML). Multi-thread technique is adopted to meet the demand of real-time sounding, Matlab engine is adopted to develop signal processing and visualization module rapidly. Addition to existing fixed frequency sounding mode and swept frequency sounding mode, a new sounding mode called auto hopped frequency sound (AHFS) is present for ionospheric sounding needs,. WISS software platform has accomplished first iteration and prototype system is applied to practical sounding. Sounding functions of radar implement by software, which means a new sounding mode could be develop rapidly. This software also provides realization platform of various automatic detection techniques and information extraction techniques.2. WISS echo automatic detection system is structured and implemented.Signal accumulation technique, constant false-alarm rate technique and denoising technique suited this system is advanced and implemented. Signal accumulation technique, including amplitude accumulation, Doppler compensated accumulation and delay-Doppler 2-D amplitude accumulation, can make weak echo detectable and significantly increase detection ability of WISS. Parametric and non-parametric CFAR technique is applied to WISS, and is proved by practical sounding. To restrain false-alarm caused by impulse noise and radio frequency interference, order statistics filter is used.3. Correction of systematic error in monostatic radar systemA simple and practical technique to use the signal energy direct coupling between the transmitting and receive antenna to correct systematic error is presents and implemented. It’s perform well in correction of systematic delay error and phase distortion4. Information extraction of WISS echo.(1) AR model of WISS echo is established, and parametric spectral estimation is used to extract echo’s high resolution Doppler spectrum. Through the high-resolution Doppler shift ionograms, different ionospheric reflection region can be given, so monitoring large-scale movement of ionosphere and inversion of ionospheric mode is suppo(?)ed.(2).Techniques to extract Doppler information from Non-stationary echo signal obtained by WISS is researched, including estimates instantaneous Doppler frequency and Doppler-time spectrum of ionosphere. These techniques are applied to effects diagnosis of Ionospheric heating experiments.