Abstract
We analyze the practical limits of a lidar system based on the use of a laser diode, random binary continuous wave power modulation, and an avalanche photodiode (APD)-based photereceiver, combined with the control and computing power of the digital signal processors (DSP) currently available. The target is to design a compact portable lidar system made all in semiconductor technology, with a low-power demand and an easy configuration of the system, allowing change in some of its features through software. Unlike many prior works, we emphasize the use of APDs instead of photomultiplier tubes to detect the return signal and the application of the system to measure not only hard targets, but also medium-range aerosols and clouds. We have developed an experimental prototype to evaluate the behavior of the system under different environmental conditions. Experimental results provided by the prototype are presented and discussed.
Highlights
The application of lidar systems began with the use of high peak-power lasers
In this type of lidar system, when very low signal is received from the atmosphere, the input yD of the A/D converter is largely dominated by noise
The use of a software-defined lidar allows for changing the operation mode of the system with the same hardware
Summary
The application of lidar systems began with the use of high peak-power lasers. Even today most of the lidar systems in use for atmospheric remote sensing are based on this principle. The use of high peak-power lasers entails two disadvantages, namely the necessary power to operate them and the lack of eye safety To overcome these problems, lasers with low peak-power and high pulse-repetition frequencies, in the tens of kHz, along with pulse-return accumulation can be used.[1] More efficient methods using continuous-wave (CW) low peakpower lasers power-modulated with sequences with properties similar to those of the sequences used in spread-spectrum communication systems[2,3] have been studied.[4,5,6] Detection using a correlation algorithm provides range resolution. The paper is organized as follows: Sec. 2 lays out the model of a system using pseudorandom sequences to modulate the power of a laser diode transmitter under the control of a DSP that is in charge of performing the correlation operations to retrieve the range-resolved atmospheric backscatter.
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