Non-linear swept frequency technique for CO2 measurements using a CW laser system

TL;DR

This paper introduces a non-linear swept frequency technique utilizing a CW laser system for simultaneous online and offline CO2 measurements, improving channel separation and cloud rejection capabilities.

Contribution

It presents a novel multi-swept sine wave system with an analytic method for orthogonal frequency determination, enhancing measurement accuracy and robustness.

Findings

Effective separation of measurement channels

Reduced sidelobes in autocorrelation functions

Improved rejection of thin clouds

Abstract

A system using a non-linear multi-swept sine wave system is described which employs a multi-channel, multi-swept orthogonal waves, to separate channels and make multiple, simultaneous online/offline CO2 measurements. An analytic expression and systematic method for determining the orthogonal frequencies for the unswept, linear swept and non-linear swept cases is presented. It is shown that one may reduce sidelobes of the autocorrelation function while preserving cross channel orthogonality, for thin cloud rejection.