| Low probability of intercept(LPI)Radar is a tactical demand for modern battlefields.The main technical means of implementing LPI radar include power management,wide bandwidth,frequency variability,low antenna sidelobe and other design attributes.The traditional LPI radar waveforms are mainly modulated by frequency or phase method.Orthogonal frequency division multiplexing(OFDM)radar which subcarriers' frequency is orthogonal,provide flexible waveform parameter selection,and the ambiguity function having the ideal pin-shaped,is a good waveform of LPI radar.With the complexity of the modern battlefield,Multi-input multiple-output(MIMO)radar has gained more and more attention based on its rich space-time frequency resources,anti-jamming and anti-intercept ability,flexible waveform design and good parameter recognition ability.And its many excellent performance comes from the orthogonality of the trans-mitted waveforms.Therefore,the orthogonal design of the MIMO radar combined with OFDM technology is related to the performance of the MIMO radar.In this paper,we focus on the design of LPI radar waveforms of MIMO-OFDM radar.The main contents are as follows:(1)The key technology and the typical waveform of LPI radar are analyzed,and the principle of OFDM radar and its low intercept performance is analyzed.LPI radar needs to adapt to the complexity of modern battlefield,and it is a modern radar to improve LPI performance of one of the effective technology,so the principles of MIMO radar were described.(2)Combining OFDM with MIMO,the signal model of MIMO-OFDM radar is studied.It mainly studies the LFM-OFDM signal model and the PC-OFDM signal model.In fact,the ideal orthogonal signal Which does not exist.It is usually required that the orthogonal signal has low peak and mean sidelobe of autocorrelation and cross-correlation.LPI performance of the MIMO radar is analyzed.The advantages of the phased array radar in the LPI performance are analyzed.At the same time,the detection distance of the MIMO radar with LPI performance is analyzed when the intercept receiver is at different sensitivities.And the LPI performance of MIMO radar when the interception receivers intercepts the radar sidelobe is analyzed.(3)The chaotic two-phase modulation of LFM-OFDM signal is proposed.Each symbol is LFM modulated by the same frequency modulation slope,which increases the signal spectrum utilization,and the chaotic two-phase modulation has "noise-like" characteristics,so it has good LPI performance.The waveform is divided into the modulation part and the orthogonal part,and the MIMO orthogonal waveform design based on CAN(Cyclic algorithm-new)algorithm is studied.Based on the CAN algorithm,Minimizing the optimization,the orthogonal part ensures that the signal has an approximately omnidirectional emission pattern;and the detection of the proximity target is good.(4)The signal processing of LFM-OFDM waveform with long pulse phase modulation with doppler tolerance is studied.This signal has doppler tolerance and can be quickly based on a single pulse to get the target distance and Doppler.And the distance information can be compensated according to the obtained velocity.The accuracy of the distance estimation of the chaotic two-phase modulation signal and QPSK is compared.The conclusion that the chaotic two-phase modulation signal has high estimation accuracy is obtained. |
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