根据闭环控制的原理,对单个目标实现速度跟踪的关键在于形成一个能时刻套住目标的速度门。使用模拟式跟踪环可以完成这一任务。一种可能的方法是在距离门中放后面用鉴频器和自动频率控制(AFC)环路来实现。这种方法是以窄带中放的通带构成速度门。当目标径向速度变化时,鉴频器输出的误差信号经低通滤波器后加到压控振荡器(VCO)上,调整VCO的振荡频率去跟踪信号的多普勒频率。这相当于误差信号控制一个速度门在频率轴上连续地移动,从而构成一个闭环的速度跟踪环路。另一种可能的方法是在中放输出端接一个多普勒滤波器组,用它覆盖预期的多普勒频移范围,通过比较相 According to the principle of closed-loop control, the key to achieve the speed tracking of a single target is to form a speed gate that can always cover the target. This can be done using analog tracking loops. One possible solution is to place the back of the range gate with a frequency discriminator and automatic frequency control (AFC) loop. This method is to narrow the band in the pass-band constitute the speed gate. When the target radial velocity changes, the error signal output by the frequency discriminator is added to the voltage controlled oscillator (VCO) through a low-pass filter, and the oscillation frequency of the VCO is adjusted to track the Doppler frequency of the signal. This is equivalent to the error signal controlling a speed gate to continuously move on the frequency axis, thereby forming a closed-loop speed tracking loop. Another possible method is to drop a Doppler filter bank in the output of the amplifier to cover the expected Doppler shift range,