一种天幕靶用弹丸信号自动识别电路

天幕靶在使用中，经常受到蚊虫、飞鸟以及冲击波和光电器件随机噪声的干扰而输出误信号．文中提出一种自动识别弹丸信号的逻辑电路，利用飞行物和干扰源穿过天幕靶视场所产生信号宽度的不同，自动识别出弹丸信号．电路的输出端仅输出弹丸信号，蚊虫、冲击波、随机干扰等非弹丸信号被滤除掉．设计的电路能同时滤除比弹丸信号宽度短和长的两类信号，短信号和长信号的宽度可以预先设置，并有电路工作选择端．设计的电路在CPLD芯片上实现．经在天幕靶上使用验证，电路工作可靠，提高了天幕靶的稳定性．

A circuit to automatically recognize projectiles signal on sky screen

Sky screens are one kind of instruments that is used to measure the velocity of flying bullet. Since the sky screen is usually placed near the cannon and works in field, the output signals are often confused with other signals such as ballistic wave, shock wave and flying insects. Present paper describes the detailed logic design of a circuit to recognize the real bullet signal from the primary outputs of sky screen. Shock wave and ballistic wave lead to signals of the shorter time than bullet,and the flying insects results in signals of the longer time. The circuit,which is fulfilled by CPLD. consists of counter,D flap-flip and digital comparator. The time width for filtering signal is set in advance. The circuit is verified enhancing the stability of sky screen.