| The ionosphere, as an interface of the Earth’s atmosphere and outer space, has produced underestimated influence on human activities. It affects broadcast, wireless communications, measurement, navigation and space exploration. With the unique method of incoherent scatter detection, Incoherent Scatter Radar(ISR) makes it possible to probe the ionosphere from the ground. Due to the special nature of the acquisition target, Incoherent Scatter Radar usually probes the ionosphere with complex transmitted waveforms. While using software on general-purpose computers to process radar signal can greatly enhance the flexibility of the entire system. Based on the construction and application of China’s first Incoherent Scatter Radar, waveform designs for Incoherent Scatter Radar are intensively discussed in this paper. While a software for signal processing is designed in this paper, too.Firstly, the detection principle and detection technology of Incoherent Scatter Radar are studied. The formation process of scattering spectra and the characteristic of low SNR of the scattered signal are analyzed, and the noise calibration method is given. With the theory of ambiguity function, the relationship between the autocorrelation function of the scattered signal and autocorrelation function of the ionospheric plasma is derived. As a key concept in signal processing, the definition of lag profile matrix is given. And the calculation method of the autocorrelation function and the power spectrum of ionospheric plasma are studied.Secondly, waveform design for Incoherent Scatter Radar and the corresponding signal processing methods are studied. The long-pulse code, the Barker codes and the two-phase alternating codes are studied. The advantages and disadvantages of the three coding types are comparatively analyzed with their ambiguity functions. A new coding type for Incoherent Scatter Radar called polyphase alternating codes is introduced. The number of available code lengths and the flexibility of the waveform design are greatly increased by the new codes. Meanwhile polyphase alternating codes have a similar ambiguity function and the same range resolution with the two-phase alternating codes have. An improved coding type called polyphase alternating codes coded frequency hopping codes is introduced. The new codes can reduce the number of transmittedpulses, and improve the detection efficiency and detection accuracy. The signal coding and signal processing methods of this new coding type are given in detail.Finally, a signal processing software based on current Incoherent Scatter Radar System is designed to improve the flexibility and reliability of the system. The functional requirements of the software are analyzed and the software is divided into four functional modules of the network module, document management module, signal processing module and the user interface module. Each module is designed, and the design ideas of each module are introduced in detail. Meanwhile, the technologies of high-speed data acquisition, efficient signal processing, multifunctional graphics and other key technologies are studied. Also the radar signal processing algorithms are implemented by the software. Finally, the entire software is tested to verify the completeness and correctness of the function of each module. And the signal processing algorithms are verified. |
PDF Full Text Request