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: Laser detection has become one of the most important detection types because of its high detection accuracy, fast response speed and strong anti-interference ability, which is the key technology in tracking, pointing and ranging detection systems. The requirements of the dynamic range and reliability of laser detection are very strict for a maneuvering flight target’s detection. For a small or long-distance target, the echo signal reflected by the target is very weak, so the laser detection circuit needs to be very high sensitive. For a large or short-distance target, the circuit is required to adapt to strong light signal and improve reliability, so the laser detection circuit should have a high damage threshold. Based on the detection requirements of high reliability and large dynamic range, as well as the strict limitation on volume and weight, in this paper it is considered that the design with only a single detector and the matching circuits realizes laser detection and reception. In the development of optoelectronic devices, the Avalanche Photo Diode ( APD ) is very suitable for the detection of laser echo signal reflected by a long-distance target. The performance of APD affects the detection performance index of the system directly. A laser detection circuit based on APD is designed to detect maneuvering flight targets in space. The high sensitivity is realized by setting suitable circuit parameters, and the high-voltage unloading function is designed to ensure that the strong laser does not damage the detector. The design greatly improves the detection dynamic range of the laser detection system. At the same time, the circuit has high signal-to-noise ratio, detection probability and high reliability. In order to achieve high detection sensitivity, the operating voltage is higher than 300 V @25 according to the requirements of APD's optimal signal-to-noise ratio. The operating voltage formes avalanche gain, and the detection sensitivity could reach the magnitude of nava. At the same time, in order to ensure the effective response of strong laser signal for the detector, avoiding irreversible damage and improving reliability, it is designed that a high voltage unloading circuit when strong pulse light signal could reach 45 mW or more. The dynamic range could reach up to 67 dB. Through the test and analysis, the design in this paper can effectively ensure the performance and reliability of the system.
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