Abstract:
The development of low-cost impedance spec-
troscopy devices is limited by the capabilities of low-cost
hardware. Impedance spectroscopy requires high accuracy
over a large bandwidth and dynamic range for most applica-
tions. In this paper, back-end signal processing solutions are
examined and implemented to improve both the bandwidth
and dynamic range of a typical low-cost impedance analyser
without modifying the hardware. The bandwidth is improved
by undersampling the input waveforms and reconstructing
the signals based on the known frequency information. The
bandwidth can be increased by multiple orders of magni-
tude and the limiting factor of the system becomes amplifier
bandwidth and the Analog-to-Digital Converter (ADC) sample-
and-hold circuit. Despite allowing signals to become orders of magnitude larger than the ADC range, the original signal
can be reconstructed based on the measured saturated signal. This saturation technique more than doubles the dynamic
range for any given accuracy requirement.
