一种用于激光脉冲测距的恒比定时电路

A Constant Fraction Discriminator for Laser Pulse Ranging

在激光雷达接收电路中,采用固定阈值比较器得到激光脉冲返回时间时,不同峰值回波信号会产生时间漂移。在传统恒比定时(CFD)电路的基础上,提出了一种窄脉冲延时电路,以替代传统RC延时结构。引入了右半平面零点,在保持增益基本不变的情况下产生相位滞后,保证信号波形不变,从而降低时间漂移效应。该CFD电路基于0.18μm CMOS工艺进行设计。仿真结果表明,在窄脉冲输入信号的上升和下降时间均为3 ns、总脉宽为16 ns时,输出信号的延时为2.05 ns。输入信号幅值范围为100~300 mV时,该CFD电路的输出上升沿翻转时间的漂移误差仅为73.6 ps。

In the design of receiver circuits of LiDAR,a fixed threshold comparator is commonly used to trigger the different peak echo signals,which could produce time walk.Based on the CFD(Constant Fraction Discriminator)technology,a new narrow pulse delay circuit was proposed to replace the traditional RC delay structure.A right half plane zero point was introduced to generate phase lag.The phase lag was generated at high frequencies while the gain was kept stable to ensure that the shape of received signal was unchanged.So the time walk effect was reduced.The proposed CFD circuit was designed in a 0.18μm CMOS process.The simulation results showed that when the narrow pulse signal had a rising and falling time of 3 ns and a total pulse width of 16 ns,the output signal’s delay time of the delay circuit was 2.05 ns.Meanwhile,when the range of the input signal’s amplitude was between 100 mV and 300 mV,the proposed CFD circuit had a time walk error of only 73.6 ps for the output leading edge.