Understanding noise-shaping in sigma-delta controls of surface potential for MOX gas sensors

Abstract

The objective of this paper is to explain how quantization noise-shaping can be achieved for the output bitstream of sigma-delta controls of surface potential (SP) in MOX gas sensors. These controllers use temperature modulation to keep constant the surface potential of the nanostructures. The rate equations describing the time evolution of the state variables in the sensing layer (concentration of ionized species on the surface of the nanostructures) are nonlinear. It will be shown that under the condition of constant surface potential, the sensor using the proposed temperature modulations can be seen as an example of affine switching and that quantization noise shaping may be achieved.