Research And Implementation Of The X-band Radar Signal Simulator

With the fast development of radar technology,radar system becomes more and more complex, and its function is increasingly diversified. However, the radar system still meets some problems: incremental difficulty in debugging, highly complicated outdoor experiment with long cycle and high cost etc. Fortunately, radar signal simulator overcomes these problems properly and provides a feasible method for the system performance analysis and algorithm evaluation of modern radar. Radar signal simulator can provide various modulation signals, including various types of amplitude modulations, phase modulations and frequency modulations, and the signals have a request of high frequency, wide band, small step, high frequency agility, low phase noise and low spurious.This paper will initially introduce the general background and development of radar signal simulator, and then specify common radar echo signal model and frequency synthesizer technology. By comparing both advantages and disadvantages of several frequency synthesizer structures based on phase locked loop and DDS, combining project’s index requirement, the author finally decide to select the direct frequency mixing structure for frequency agility and phase modulation. We select a high-frequency reference clock DDS to output the high frequency signal while considering the design difficulty of the band-pass filter after the mixer. Moreover, the whole design detail and the test result of this system will be presented. Summary is the final part of this paper.The radar simulator in this subject has two output channels: RF_L and RF_H. The center frequency of RF_L channel is 1GHz, while the center frequency of RF_H channel is 9.5GHz, and they have the same band-width which is 50 MHz.The low frequency multi-mode signals in the RF_L channel is generated directly by the DDS controlled by FPGA. The spur of this signal is less than-64 dBc, phase noise at 100 kHz offset is better than-104dBc/Hz. The X-band radar signal of RF_H channel is generated by the mixing between the DDS output and the local oscillator. The spur in RF_H channel is less than-58 dBc, phase noise at 100 kHz offset is better than-92dBc/Hz. The simulator is required to produce 10 signal types, such as Linear Frequency Modulation Continuous Wave, inter-pulse stepped frequency and phase modulation.The design solution and process of the radar simulator in this subject would have some reference value for other similar design work.