Design And Analysis Of LPD Communication Waveforms Based On Joint-agility Of Time-width And Waveform Bases

With the development of non-cooperative communication signal processing and weak signal detection based communication reconnaissance technologies,currently existing communication waveforms with low probability of detection(LPD)are facing more and more challenges.To improve the crypticity of communication waveforms in various domains,a novel design approach for communication waveforms based on joint agility of time width and waveform bases is proposed in this thesis,due to the fact that the varied time width(VTW)and waveform bases have the potential of boosting the crypticity of the periodic characteristics and time-frequency domain convergence for communication waveforms.Then,the LPD performance of VTW non-single frequency(VTW-NSF)based communication waveform is also evaluated.On the basis of VTW-linear frequency modulation(VTM-LFM)and VTM-sinusoidal frequency modulation(VTM-SFM)communication waveforms,a novel waveform based on joint agility of time width and waveform bases is proposed in this thesis,namely,joint VTW-chirp/sinusoidal frequency spread spectrum(VTW-C/SFSS).The performance of the proposed waveform is evaluated in terms of channel adaptability and crypticity in various domains.Firstly,a finite set of LFM and SFM waveforms is constructed.Their corresponding mathematical models in various domains are presented as the mathematical basis for performance analysis of these waveforms,including bit energy,orthogonality of waveform set,correlation function,power spectrum density(PSD),distribution functions in fractional Fourier transform(Fr FT)and sinusoidal frequency modulation transform(SFMT)domain,etc.Secondly,a framework for VTW parameters configuration is introduced to support the agility of time width for communication waveforms.Then,a VTM-LFM based communication waveform is proposed.The impact of VTM configurations on the characteristics in various domains and channel adaptability is also analyzed for the proposed waveform.Thirdly,to tackle the high sidelobe problem of autocorrelation function due to the periodicity of FM function,a half-cycle VTM-SFM waveform is proposed to optimize its corresponding autocorrelation characteristic.Moreover,the impact of VTM configurations on the waveform characteristics in various domains and channel adaptability is evaluated for the proposed waveform.Finally,by adopting the philosophy of joint agility of time width and waveform bases,a VTW-C/SFSS based LPD communication waveform is proposed.Furthermore,the influence of VTM configurations and agility of waveform bases on the flatness of ESD and the dispersivity of time-frequency energy convergence is analyzed for the proposed waveform,respectively.