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一、常规雷达常规的模拟式雷达采用的是所谓的“联机”信号处理方法,也就是说,观测员从雷达荧光屏上看到的回波信息实际上也是雷达设备几乎在同一时刻接收到的回波信号。用这种常规方式显示目标数据的雷达,由于有效时间或显示时间或重复周期之比有时极为不利,其显示亮度难免要受到一定限制。图1示出测量距离为1海里时的时间比。由图可见,有效时间为12微秒,因为只有在这段时间内才能激励显示管荧光层发亮,而相对该时间的无效时间(消隐时间)有488微秒。多年来,雷达研制厂家一直力图通过选用特殊的显示管或者提高脉冲重复频率来解决近距离测量时亮度过小这一难题。但是,未能取得真正令人信服的结果。二、数字信号处理正如上节所述,雷达设备可达到的图象亮度也是显示时间与消隐扫描时间之比的函数。在耗资合理的情况下对“联机”工作的雷达加以
I. Conventional Radars Conventional analog radars use so-called “on-line” signal processing methods. That is, the echo information seen by the observer from the radar screen is actually what the radar equipment has received at almost the same time Wave signal. Radars displaying the target data in such a conventional manner are inevitably subject to certain restrictions due to the extremely unfavorable ratio of effective time or display time or repetition period. Figure 1 shows the time ratio when measuring a distance of 1 nm. As can be seen from the figure, the effective time is 12 microseconds, because only in this period of time can be excited to show the tube fluorescent layer, and the relative time of the invalid time (blanking time) 488 microseconds. Over the years, radar manufacturers have been trying to solve the problem of too little brightness at close range measurements by using special display tubes or by increasing the pulse repetition frequency. However, no truly convincing results have been achieved. Second, the digital signal processing As mentioned in the previous section, the radar device can reach the image brightness is also a display of time and the ratio of blanking time scan function. The “on-line” radar should be used at reasonable cost