Analysis Of Non-linearity Of Radar System Based On Simulation

The application of radar in the military equipment,civil areas and research projects is getting more and more widely,which has got the attention of countries around the world.Signal is the core of the radar system.Direct digital waveform synthesis(DDS)technology has been widely used in practical radar engineering due to the realization of flexibility,and the accuracy of high output frequency.In addition,with the development of digital technology,digital IF technology has also been introduced into radar transmitter and receiver systems.This also further enhances the flexibility and accuracy of the radar system.In order to improve the radar detection capability,radar signal processing generally take the matching filter,assuring the output signal to noise ratio to achieve maximum.Of course,the inherent causes of signal generation and the restrictions of the analog devices will introduce complex spurs and interference to the received signal,which will also have a great impact on radar performance.In this paper,nonlinearity of the stray source and radar system are analyzed in detail.Firstly,the basic principle of direct digital waveform synthesis technology is introduced,and then the different spurious components in DDS output signal are analyzed in detail,including phase truncation spurious,amplitude quantization noise and nonlinearity of DAC.Then,the intermodulation characteristics caused by the non-linearity of the analogue devices in the radar transmitting and receiving link are introduced,and the quantitative relationship between the non-linear indexes is deduced.Radar system is modeled and simulated based on system vue.This paper focuses on the simulation of the nonlinearity of DDS and radar T/R system.A linear frequency modulation signal is generated by DDS,and the spurious of the chirp signal is deduced according to the stray of the single frequency signal.Influence of the spurious on radar detection is analyzed,which reduce the output signal to noise ratio and affect the sensitivity of radar detection.Analysis of the nonlinearity is mainly on the influence of the intermodulation interference caused by the non-linearity on the radar detection in different target environments.Simulation shows that in the monocular or multi-target environment,non-linearity of the transmitter will not have an impact on signal processing.But the nonlinear characteristics of the receiver in a multi-target environment will generate intermodulation interference which produces false targets.