Impedance analyzer using square wave stimuli

Abstract

A microcontroller-based system for measuring the impedance of a device under test (DUT) () responsive to a square wave stimulus. A clock generator circuit () in the microcontroller () generates a clock signal at a base clock frequency. A first timer () divides down the base clock frequency by a first frequency divisor integer to set the stimulus frequency of a square wave generated by a general purpose input/output (GPIO) function (), and a second timer () divides down the base clock frequency by a second frequency divisor integer to set the sampling frequency of an analog-to-digital converter (ADC) (). A discrete Fourier transform executed by a processor () is used to determine the impedance of the DUT at the stimulus frequency. The first and second integers are selected so that aliased harmonics fall in different DFT bins from the fundamental tone.