Research On Radar Communication Integration Based On Shared Waveform

The integrated design of radar and communication will make the equipments a whole to satisfy radar functions and communication functions.Sharing waveform is one of the mainstream,which can enable integrated equipment to share hardware resources and spectrum resources such as transceiver antennas and signal processing modules,thus effectively reduce system hardware costs,the interference between devices and the equipment weight.This thesis studies two common sharing waveforms: linear frequency modulation(LFM)and orthogonal frequency division multiplexing(OFDM)signal.The main research contents include:1.In view of the serious spectrum expansion problem after information modulation in a LFM integrated signal,which is typically modulated by minimum shift keying(MSK)or Gaussian MSK(GMSK),one of the existing solutions is to modulate fixed code elements at the beginning and end of the signal.Base on this solution,we propose an algorithm for flexibly determining the number of fixed code elements at the beginning and end of the signal within the given acceptable spectrum expansion range,according to the modulation information,which can effectively reduce the number of fixed code elements required at the beginning and end of the signal and reduce the loss of information transmission rate.Considering the need for communication between UAV friendly forces and the requirement to determine the location of friendly parties,a carrier frequency estimation method based on distance search is proposed.When the bit error rate of the fixed code segment is still high after frequency and phase compensation through ranging at the receiving,the distance search would be carried out and the final ranging and frequency phase estimation will be determined by the maximum mutual correlation operation,which effectively improves the accuracy of ranging and estimation.2.Aiming at the problem of low spectrum utilization of information modulation on LFM signal,a waveform called LFMc(LFM Combination)is proposed by truncation and recombination of LFM signal,and the information is represented by different recombination methods.It is found that the spectral spread of this signal is lower than that of LFM＿MSK\GMSK signals,and the pulse compression peak sidelobe ratio is lower.In the signal relay scenario,the LFMc signal can be combined with MSK or GMSK modulation to achieve a similar effect of code division multiplexing and further improve the frequency band utilization.The radar and communication performance of multicarrier OFDM＿LFM integrated signals are also studied.3.Aiming at the problem that the radar performance of the OFDM signal is easily affected by the modulation information,a variety of sequences with good autocorrelation and cross-correlation properties are selected to pre-modulate the OFDM signal,which effectively improve the poor performance when the modulation information has a large number of repeated code elements.Considering the problem that the peak value of OFDM signals is relatively high,the performance of CE＿OFDM signals based on constant envelope technology in radar and communication is studied.4.Since multi-carrier signals OFDM＿LFM and OFDM integrated signals might be inefficient due to channel reasons when the average power distribution of subcarriers strategy is utilized,combined with UAV stealth,as well as radar and communication performance requirements,the minimum power constraint is considered to meet the detection distance obtained by the radar equation,the conditional mutual information is taken as the radar performance indicator,the channel capacity as the communication performance indicator,and adding the peak to average power ratio as waveform indicator.A genetic algorithm is utilized to optimize the power distribution under the environment with Gaussian noise and clutter.