Andrea Chighine

University of Edinburgh - Institute for Digital Communications (IDCOM)

An FPGA-based lock-in detection system to enable Chemical Species Tomography using TDLAS

Abstract:

In this talk we present the design, implementation and test of a compact, low-cost and fully digital signal recovery system for tunable diode laser absorption spectroscopy (TDLAS) in narrow line-width gas sensing applications. An FPGA-based digital lock-in amplifier (DLIA), in conjunction with TDLAS using the wavelength modulation spectroscopy (WMS) technique, is utilized to demodulate and extract first (1f) and second (2f) harmonic signals for a narrow CO2 feature in the spectrum region of 1997.2nm. The spectrum in this wavelength region shows suitably weak water absorption, enabling CO2 detection with high resolution. Gas-cell experiments were carried out using the DLIA and a conventional rack-mounted commercial lock-in amplifier. The comparison between the two systems shows good agreement, validating the feasibility of this approach and demonstrating the prospect for extension to a massively multi-channel system to implement Chemical Species Tomography.

Keywords: Field Programmable Gate Arrays (FPGA), Lock-in amplifier, Digital demodulation, Tuneable Diode Laser Spectroscopy (TDLAS), Chemical Species Tomography (CST)

Info: Andrea Chighine is a PhD student at the Agile Tomography Group at the Institute for Digital Communications, University of Edinburgh.