激光回波小信号宽带放大器设计

Design of wideband amplifier of weak laser echo signal

设计了一款激光回波小信号宽带低噪声放大器。选用低噪声、高带宽电流反馈型差分运算放大器THS4509,采用两级放大电路结构以获得较大的放大倍数,利用传输线变压器实现输出信号由双端到单端转换。为减小噪声,采用过渡带特性最好的椭圆低通滤波器滤除带外噪声。经实验验证,该放大器具有40dB放大倍数、120 MHz带宽和小于10mV(pp)的系统噪声,能对各种反射率条件下不同目标反射回的微弱激光小信号进行有效放大,较好地解决了远距离和低反射率目标物体测距问题,实际测试测距量程可达450m。

A low-noise and wide-band amplifier was designed for the weak laser echo signal.We chose the CFB differential operational amplifier THS4509 with low noise and high bandwidth as the core component;a two-stage amplification circuit was adopted in order to obtain a larger gain,and a transmission-line voltage transformer was used to change the output signal from double-ended to signal-ended.To reduce the noise,we used a low-pass elliptic filter with the best transition zone features to filter out the noise outside the band.The experiences demonstrated that the amplifier had the characteristics of 40 dB gain,120 MHz bandwidth,and its noise was less than 10mV（pp）.It could effectively amplify the weak laser echo signal reflected by the different target objects even with a variety of reflectivity. Furthermore,the amplifier with the above characteristics performed better in solving the problem of long distance and low reflectivity,and its maximum measuring rang can reach 450m proved by actual tests.