When detecting ultrahigh speed micro targets, because the photon Doppler signal will be seriously interfered with by high-frequency noise, it is difficult to accurately extract the beat frequency information, resulting in serious speed demodulation error. Therefore, we propose a beat frequency extraction method for high-speed and high-noise Doppler signals based on double correction, which can accurately correct the beat frequency signals of high-frequency noise interference. First, the ratio correction method is used for the first spectrum correction to screen out the normalized spectrum of high-frequency noise interference; then, according to the degree of noise interference, the energy barycenter correction method or linear interpolation method is used for the second spectrum correction. Numerical simulation results show that this method can reduce the spectral error by 1.6% to 2.1%. We used this method to process the Doppler signal from the detonation small flyer experiment in Initiating explosive device testing.The results show that it can reduce the beat frequency error by 1.83 times at most under highfrequency noise interfered, equivalent to the instantaneous velocity error of 1955 m/s can be decreased after velocity demodulation. Therefore, the beat frequency extraction method based on double correction has good noise resistance and reliability. We corrected the different regions' frequency spectrums according to the noise interference intensity, which provides an idea for the beat frequency extraction of high-speed and high-noise Doppler signals.
Flash detectors are mainly used to detect the brief light flashing when projectiles are launched or exploded in the air. They can output trigger pulse signals in real time to start a test instrument and carry out data collection. Because flash detectors cannot work reliably under strong background light radiation, this work studied the flash detector mechanism. The influence of background light radiance, lens aperture, and detection distance on the effective signal was analyzed, a mathematical model of detection sensitivity based on the background radiation brightness control was proposed, a mathematical formula of the detection distance of the flash detector was deduced, and the optimal working conditions were obtained. The researched model was verified by simulation analysis and actual test experiments, in the same external circumstances, the limit detection distance of the optimal aperture compared to the maximum aperture increased by 20%, and the effective signal voltage amplitude was twice the amplitude at the maximum aperture, and the results showed the correctness of the analysis. The proposed detection sensitivity model can be applied for a dynamic photoelectric detection instrument, which broadens its potential application in the engineering field.
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