Design And Implementation Of Wideband Amplifier Of Laser Small Signal

Compared with other ranging technologies, laser ranging has many advantages, such as strong anti-interference ability, high accuracy, distant measurement, and it can work under any condition of weather and it has many other advantages, so it is widely used.In recent years,3D laser scanner based on the laser ranging technology is pushing the rapid development of the areas of mobile measurement and 3D imaging map and etc. It plays very important role in the national economic and national defense construction.As one of the core components of 3D laser scanner, the main function of analog circuit is to amplify the laser small signal, and its performance may directly impact the accuracy and the length of distance measurement. Therefore, the front analog circuit needs to overcome several key technical problems as following:wide dynamic range, analog circuit should have wide dynamic range in order to adapt to the needs of different distance and reflective target’s measurement; high magnification, analog circuit needs large amplification to amplify weak pulse signal for long distance and low reflective target; wideband, the single pulse width of 3D laser scanner usually in ns level and its bandwidth of energy distribution is very wide; low noise, reducing noise and improving the signal noise ratio to improve ranging accuracy.In this paper, the main research is aimed at solving the several key technical problems above. Firstly, this thesis has analyzed the characteristics of the laser pulse echo signal, taking the requirements of laser ranging into consideration, and got the design technique index of wideband amplifier of laser small signal in this paper. Then, put forward the design scheme of multi-channel, with the wide dynamic range of laser ranging considered. Finally, described the design of the wideband amplifier of laser small signal by module in detail.This paper has used the high response speed and high sensitivity’s indium gallium arsenide APD as the front photoelectric detector, and used the trans-impedance amplifier as the circuit structure, and designed a wideband with high sensitivity and low noise photoelectric conversion circuit, which has a magnification of 69.5dB. In order to reduce the noise, this paper has used the elliptic filter which has a best performance of transition band, then designed a 9 steps filter with 120MHz’s bandwidth; used a high speed current feedback amplifier as the main component, and designed a wideband amplifier with magnification of 28dB.By verifying the experiment in this thesis, the design of analog circuit is simple and practical, with small volume, and it has a 120MHz system bandwidth,97.5dB system magnification and 50mVpp overall system noise. It can amplify the weak laser small signal effectively which is reflected by the different target objects under the condition of all kinds of reflective target. After testing, the minimum laser detection sensitivity of the analog circuit is 1.1uw and the effective distance of measurement is longer than 300m. At present, it has been applied successfully in the first high precision of 3D laser scanner which is researched and developed independently by Wuhan Hi-target.