Laser Radar Receiver System Noise Characteristics

Laser radar has been extensively used both in military and civilian affairs. It is a focus in the high-tech fields at present. For the investigation of the laser radar, not only the establishment of the setup is necessary but also the study of its performance and applications. There are a lot of factors including atmospheric transmission, target characteristics etc. that could influence the performance of laser radar. Usually, the ladar's performance could be verified through experiments and theoretical research. However, computation simulations are also frequently used to improve the system's performance. The simulation could save the research expenditure and the system's parameters and all the other influences could be varied freely. The established model includes emitter and receiver. In the model of the receiver, the core is the foundation of photoelectric detector; then the amplifier, filter and peak detection. Noises characteristics of the receiver have been investigated in this paper in detail. Methods and new designs are proposed and demonstrated through simulation. It has practical significance for the development of laser radar and other signal detection fields.The characteristics of the receiver are first analyzed; a laser pulse model is then created to simulate the laser source. An Automatic-Gain-Control system is designed to stabilize the gain of amplifier of APD, and the noises characteristics of APD, TIA noises are all studied. The factors which could lead to the strong noises including the temperature, the gain, bias voltages and other influence parameters are all included in the model. An active reverse-biased voltage compensation method to stabilize the gain of APD used in laser radar was studied independently. The simulation results show that this system could stabilize the gain and increase the signal-to-noise ratio of APD. For TIA method, the difficulty is the selection of the appropriate parameters to reduce noises while keeping the gain and bandwidth the same value. Some conclusions are obtained through the research about the influences of noises, temperature, gain and frequency on TIA. In the light of the speciality of laser radar, some appropriate parameters are chosen and a shunt-shunt feedback model is established. The simulation experiments give the preferable output results. In the last part, a automatic gain control methods based on logarithmic algorithm are designed for laser radar system. The simulation shows a feasible result.