A scalar interpolator/compressor for the improvement of sensor linearity

A hardware linear interpolator with logarithmic and exponential curve slope correction is described in this paper allowing real time linearity improvement of low resolution sensors like the miniaturized, wearable or implantable ones used for health monitoring. A compression is performed by the interpolator when the input signal is sparse or changes with low frequency. A signal distorted by the digitization process can be approximated even when its available samples are in nonuniform distances. Multiple interpolators with identical or increasing resolution can be connected in series. A three-stage interpolator with 9-bit input and 12-bit output typical resolution is implemented using 14% of the Logic Elements of an Altera Cyclone III EP3C25N Field Programmable Gate Array and is tested using an ADC developed by the author. An improvement close to 100% has been measured at the Signal to Noise and Distortion Ratio (SNDR) and at the Spurious Free Dynamic Range (SFDR) of the ADC when a 2MHz sinusoidal input was used.