Study On Measured Jamming Data And Anti-Jamming In Radar

Information is the key to master the initiative in modern warfare.It is necessary to get useful information while hindering the enemy's detection of that.Anti-jamming is the preliminary work of signal detection.To suppress interference effectively,it is necessary to acknowledge the characteristics of interference.Time-frequency analysis method has been widely used because of its adavantages in processing non-stationary signals.In this thesis,the methods of time-frequency analysis and the anti-jamming are studied.The main work is summarized as follows:First,different types of active interference and their characteristics are introduced.The barrage interference and deceptive interference are studied in detail.Some of them are described in combination with the simulation,such as the noise amplitude modulation signal,the noise frequency modulation signal and the forwarding interference of deceptive interference.Many characteristics are gained from the results,which lays the foundation of the following chapters.Then,the common time-frequency analysis methods and their properties are introduced.The main methods are Short-time Fourier transform(STFT)and Wigner distribution.Based on the definition of STFT,it can be concluded that the window function and its length affect the energy aggregation.The cross-term in Wigner while processing the additive signal leads to the appearance of kernel function,and the time-frequency concept is put forward according to the kernel function.Then STFT and Wigner are compared by processing the measured data.Fractional Fourier transform(FRFT)is introduced next.It mainly researches the special order of FRFT in linear frequency modulation signal(LFM)focuses,which provides the theoretical basis for the suppression of LFM.Finally,anti-jamming methods are researched.Through the analyses of sidelobe cancellation and blanking,we conclude that sidelobe cancellation has disadvantages in suppressing pulse interference,but sidelobe cancellation and blanking can supply each other while using together.Then it is verified that additional delay section can improve the cancellation performance to a certain extent.For the noise amplitude modulation signal,methods based on frequency domain can be used to suppress the interference signal.For the noise frequency modulation signal,time domain direct cancellation method based on signal reconstruction is introduced.The chirp interference signal appearing in the measured data can be suppressed by the nature of LFM signal focusing in specific order of FRFT.This part finally uses the measured data to validate the above methods.