Design Space Analysis for a Digital Lock-In Amplifier for Infrared Gas Sensor Signal Acquisition

Climatological conditions study has gained interest nowadays due to their effect in human life. Air quality evaluation, both indoors and outdoors, is an important concern in cities, industries and workplaces. Sensors used for this task deliver small signals that need to be cleaned and processed on-the-edge. In this paper, the authors present a processing system based on a digital Lock-In amplifier for an NDIR CO2 sensor as part of a multi-sensor instrument capable of measuring different meteorological magnitudes. Both in space applications or IoT systems, factors such as maximum area, processing time and power consumption must be considered. To this purpose, two different implementations for the same processing system are presented, a purely hardware architecture and a software implementation on a soft-core microprocessor, based on the RISC-V, both onto a Microsemi FPGA. Performance, resources usage and processing time are compared in both implementations in order to study their scalability towards a multi-sensor system.