Timer-based Demodulator for AM Square Signals coming from Sensor Circuits

This work evaluates the performance of a timer-based demodulator applied to low-frequency amplitude-modulated (AM) square signals coming from sensor circuits. The demodulator extracts the amplitude of the AM square signal by measuring the period of a reference signal that is altered by the AM signal itself, as already suggested in a previous paper but for AM sinusoidal signals. The demodulation and digitization are carried out simultaneously via a digital timer and without requiring a rectifier, a mixer, a low-pass filter, or an analog-to-digital converter. In addition, a new method to extract the amplitude of the AM square signal, which cannot be applied to the sinusoidal case, is experimentally presented. This method shows advantages in terms of linearity, data processing, and simplicity of the circuitry to generate the signals involved in the measurement.