Research On Shared Waveform Of Radar And Communication Based On OFDM

The radar and communication sharing is to solve the problems of resource shortage,high cost and function conflict when the traditional communication radar system is superimposed.It has the advantages of resource intensification and function enhancement.Common sharing methods include sharing software or hardware resources such as signals,antennas,channels,etc.,to achieve radar detection and imaging functions without affecting data communication functions.The use of waveform to share radar and communication functions has the advantages of simplifying the structure,saving spectrum resources,avoiding large amounts of electromagnetic interference,and improving the working efficiency of radar and communication systems.Orthogonal frequency division multiplexing(OFDM)waveform is a common one in radar communication sharing system.OFDM waveforms are widely used in communication that have the advantages of good anti-interference ability,high speed transmission ability and flexible subcarrier modulation.At the same time,the OFDM waveform is also widely used in the field of radar based on the advantages of good spectrum utilization and large time bandwidth product.In view of the application advantage of OFDM in radar and communication system,communication radar waveform sharing based on OFDM can be designed to give consideration to both radar and communication performance.This dissertation mainly studies the communication sharing method based on OFDM waveform radar,and the main research contents include:1.According to the good orthogonality of RMM-OFDM(Random Matrix Modulation-OFDM)radar imaging waveform,a shared communication method using random matrix modulation is proposed.Using the orthogonality between the RMM-OFDM waveforms,this dissertation realizes the shared data communication while realizing the Synthetic Aperture Radar(SAR)imaging.In addition,the influence of the randomness of communication data on the imaging ability of OFDM radar is effectively solved,and the communication function is realized on the basis of almost no influence on the imaging ability of radar.At the same time,this dissertation realizes the non-interference waveform sharing of radar communication with a small processing complexity at the receiving end.2.For OFDM-GQ(OFDM-Goutelard Q-Aary)sequences,the autocorrelation gate lobe appears periodically and the radar detection ability is poor.In this dissertation,the relationship between the autocorrelation function of OFDM-GQ waveform synthesis signal and the emission pattern of the frequency controlled array is analyzed.It is proposed to adjust the carrier frequency interval of the frequency-controlled array according to the parameters of the OFDM-GQ waveform to control the energy peak period of the transmission pattern,so as to greatly reduce the autocorrelation gate lobe of the composite signal of OFDM-GQ waveform,which proves the radar detection ability of the waveform.In the meantime,a time-sharing system is proposed to realize radar communication sharing.Finally,the simulation results verify the communication transmission performance of the waveform.3.In this dissertation,two radar communication sharing schemes based on Fractional Fourier Transform(FRFT)are designed.Based on the characteristics of single frequency signal and linear frequency modulation signal in the fractional domain,the fractional domain characteristics of traditional OFDM signal and traditional OFDM-LFM signal are analyzed.A method is designed to realize radar imaging function of traditional OFDM waveforms in communication data transmission by using fractional Fourier transform and weighted compensation.Furthermore,A modulation method using inverse fractional Fourier transform(IDFRFT)is proposed to realize the modulation and demodulation of the traditional OFDM-LFM waveform and radar imaging using the traditional range Doppler imaging algorithm through multiple transformations.