FPGA Realization Of Radar Sidelobe Cancellation Technology

With the development of information technology, the electromagneticenvironment radar system work in is getting worse. Active jamming is the mostdifficult for radar system to barrage, because jamming can enter radar system throughantenna side-lobes, which have an severe influence on the performance of radarsystem, and any method can dispose it. Adaptive side-lobe cancellation technology isone of the most effective ways to suppress active interference, which are widely usedin satellite, radar and other areas. It suppress the interference signal by forming Beampattern zero point in interference direction through auxiliary passages, which usingspatial filtering techniques.The paper based on a phased array radar and make the adaptive side-lobecancellation system as research object, discussed a number of issues about the designand engineering implementation of adaptive side-lobe cancellation system. Theadaptive side-lobe cancellation system need to reach cancellation ratio at15dB whentwo strong interference signals enter from antenna side-lobes. The system of side-lobecancellation consist of the auxiliary channel module, digital signal processing module,amplitude and phase weighting module and the main channel cancellation module.The function of auxiliary channel module is to receive and process the signal fromauxiliary channel antenna, such as low pass filtering, low noise amplification,frequency mixing, digital to analog conversion. The digital signal processing moduleselect FPGA as the hardware platform, and complete the function of IQ quadraturedown conversion, signal channel correction, interference detection and interferencesuppression. The main function of IQ quadrature down conversion is to convertdigital signal into a baseband digital signal; Channel Calibration main achievement ofthe amplitude and phase consistency correction of auxiliary channel; Interferencedetection main achieve the goal of detecting the auxiliary channels to see whether itcontain interference signals; interference suppression achieve the goal of calculatingthe weighting coefficients via the auxiliary channel LMS algorithm. Amplitude andphase weighting module achieve the goal of convert weighting coefficients intoamplitude and phase control words, and implement the weighted sum of theauxiliary channel amplitude and phase. The main channel module achieve thefunction of cancelling interference signals from the main channel through theweighted sum of the auxiliary channel amplitude and phase. The paper mainly complete the digital signal processing module functionaldesign based on FPGA, and then simulate the adaptive side-lobe cancellation systemusing Matlab to analyze the performance of the adaptive side-lobe cancellation system.Simulation results show that the adaptive side-lobe cancellation system perform wellin suppress active interference. It can suppress two strong active interference, andcancel ratio can reach15dB, and it can meet the design requirements.