Research On Integrated Radar And Communication Signal Based On LFM Signal

With the development of science and technology,combat platforms will be equipped with more electronic devices with different functions for adapting into different situations in war.However,too many electronic devices will increase the platform volume,deteriorate the electromagnetic environment and reduce the overall performance.The integration of electronic equipment systems is an important means to solve such question.Radar systems and communication systems are widely used in combat platforms.The integration of radar communications is an important aspect of the integration of electronic equipment systems.This thesis mainly studies the sharing method of radar communication function based on the shared signal.According to the linear frequency modulation(LFM)signal,the MSK-LFM signal,the multi-carrier LFM signal,and the piecewise linear frequency modulation(PLFM)signal were designed and analyzed.In this thesis,Minimum frequency shift keying(MSK)is modulated onto LFM to generate MSK-LFM signal,and its spectrum and ambiguity function are discussed,while MSK-LFM has the same Doppler resolution as LFM,regardless of the modulated data.The distance resolution is related to the amount of modulated data and the bandwidth.The modulated data makes the MSK-LFM more susceptible to Doppler mismatch.This thesis analyzes two kinds of emission methods: coherent pulse and non-coherent pulse in accordance with the requirements of the integrated system.The method of suppressing the spectrum leakage,the method of demodulating data,and the communication performance under different transmission modes are studied.According to the relationship between the LFM and the transform parameters of Fractional Fourier Transform(FRFT),this thesis proposes a multi-carrier shared signal based on LFM parameter modulation.Its main carrier adopts the fixed parameter LFM to implement radar function,while the subcarrier modulates communication information by changing the LFM of the FM slope and carrier frequency.The ambiguity function,parameter design method,the target detection and system performance of the shared signal are both carefully studied and analyzed.Simulation results show that this signal has a lower bit error rate,and the demodulation method has a certain Doppler robustness.Reasonably designing the mixing ratio of FM slope and carrier frequency can make the shared signal have better bandwidth efficiency and anti-jamming performance.This thesis proposes a PLFM shared signal with constant envelope and fixed bandwidth.The LFM is divided into time-frequency continuous three-segment signal.The bandwidths of the first and third segments are equal in duration and opposite to the polarity of the second segment.The first and third segments have the same timewidth and bandwidth,and the FM polarity is the opposite of the second segment.Data modulation is performed by changing the time width and FM polarity of the second stage.The spectrum,ambiguity function and resolution are analyzed.The results show that the distance resolution is related to the first/third segment's bandwidth,and the Doppler resolution is related to the modulated data.Using the FRFT to demodulate the data,the demodulation process is robust to Doppler.At the same time,the PLFM signal has the same detection probability as the LFM signal.