Fast and robust estimation of resonant sensors signal frequency

This paper presents a method for robust and accurate real-time frequency estimation when a square wave affected by impulsive noise is considered. The method is designed for signals coming from typical resonant sensors having frequency from 1 MHz to 10 MHz. It is based on digital modulation and numerical signal processing of the observed square wave. A prototype board has been developed in order to prove the performances of the technique, based on a floating-point digital signal processor (DSP) and a 16-bit analog to digital converter (ADC) at the sampling frequency of 48 kHz. Experimental results show that glitch immunity greatly improves with respect to the classic solution based on counting devices. Moreover, a good resolution (10/sup -7/) is observed even at a short measuring time (10 ms).