Design And Research Of Ultra-wideband CPPM Radar Signal Source Based On FPGA And SRD

Chaotic Pulse Position Modulate(CPPM)was first introduced in the field of communication.It is one of the main research contents of chaotic communication.It was originally applied to secure communication and aims to solve the problem that chaotic communication is susceptible to channel noise and distortion.Inspired by chaotic communication,CPPM signals are gradually applied to target detection and radar detection.In an ultra-wideband(UWB)radar system,the CPPM signal is used as the transmission signal,and the Gaussian pulse is most commonly used for the modulation pulse.However,Gaussian pulse has a large amount of DC component in the low frequency region and its vicinity.The antenna radiation efficiency is extremely low,which will seriously affect the transmission of the signal through the antenna and the transmission of other components,and ultimately affect the design of the UWB antenna and related systems.The research shows that the single-cycle pulse can effectively improve the radiation efficiency of the antenna compared with Gaussian pulse.For this reason,an ultra-wideband CPPM signal source with modulated pulse as single-cycle pulse is designed to improve the radiation efficiency of UWB radar antenna.Previously,the author's research group used high-speed serial transceivers to generate narrow pulse signals,which achieved better integration,miniaturization,and reliability.However,high-speed serial transceivers can only produce signals with positive polarity.Generate a single-cycle pulse that meets the criteria.In this paper,considering the above shortcomings,a FPGA and a step-recovery diode(SRD)-based analog circuit are combined to design a CPPM signal generator with a modulated pulse as a single-cycle pulse.Simple,low power consumption and low cost,this paper is based on the CPPM radar signal source with modulated pulse as single cycle pulse.The design of the hardware circuit is introduced and the following work is expounded:1.Several common UWB radar signal sources are summarized and their advantages and disadvantages are analyzed and compared.The principle of CPPM signal is introduced.It is proposed that the single-cycle signal is used as the modulated pulse signal of CPPM,which effectively reduces the energy of the DC low-frequency region,thereby improving the radiation efficiency of the radar antenna.2.The modulation method of CPPM signal is studied.Several common one-dimensional discrete chaotic maps are introduced.The Lyapunov exponent,correlation,probability distribution function and data word length versus sequence periodicity of Logistic map and Tent map are analyzed.Influence,choose ergodic and aperiodic Tent map as the modulation function,digital simulation and modulation of CPPM signal through FPGA.3.Based on the working principle of radar signal source,the selection of electronic devices is introduced.The principle of SRD and other devices is analyzed.A narrow pulse generation circuit with SRD as the core is designed.The CPPM signal generated by the FPGA module is designed.Further narrowing and single-cycle pulse shaping,a single-cycle pulse with a main pulse width of 590 ps,a main peak-to-peak value of-1.76 V,and a good waveform was obtained.The autocorrelation operation results show that the signal has good anti-interference ability and high detection probability;the spectrogram shows that the signal has no DC component and has very little energy in the low frequency region.When used as the radar signal,the radar can effectively improve the radar.Radiation efficiency of the antenna.Finally,through the research of fuzzy function,the feasibility of the developed signal source as radar transmitting signal is demonstrated again.4.The ultra-wideband radar system was built,and the structure,principle,experimental device and instrument of the ultra-wideband ranging radar system were introduced.The CPPM radar signal source developed by the application was used for ranging,distance resolution and wall penetration experiments.The experimental results were analyzed and summarized,and the feasibility of the signal source as radar detection signal was verified again.