Adaptive digital filter for improved measurement accuracy in an electronic instrument

A method for improving measurement accuracy in an electronic instrument, comprising:

• (a) coupling a calibration signal comprising a square wave having known amplitude and frequency characteristics to a front-end circuit during a calibration phase;
• (b) measuring said calibration signal with an over-sampling analog to digital converter which receives said calibration signal through said front-end circuit and generates a stream of calibration measurement values which forms an estimate signal;
• (c) optimizing a set of digital filter values according to a least-means squares mathematical algorithm to minimize the overall difference between said calibration signal and said estimate signal;
• (d) replacing said calibration signal with an input signal to be measured during a measurement phase;
• (e) measuring said input signal with said over-sampling analog to digital converter which receives said input signal through front-end circuit and generates a stream of measurement values;
• and
• (f) digitally filtering said measurement values with a finite impulse response filter which uses said set of digital filter values to obtain normalized measurement values.

An electronic instrument with enhanced measurement accuracy, comprising:

• (a) a front-end circuit having an input for coupling to an input signal, said front-end circuit having a frequency response;
• (b) an over-sampling analog-to-digital converter coupled to said front-end circuit to receive said input signal and produce a measured signal comprising a stream of measurement values at a sample rate at least twice the highest frequency of said input signal;
• (c) a calibration signal source for coupling a calibration signal having known amplitude and frequency characteristics to said input of said front-end circuit during a calibration phase wherein a set of digital filter values are optimized so as to minimize the differences between said measured signal and said calibration signal;
• and
• (d) an adaptive digital filter coupled to said over-sampling analog-to-digital converter to receive said measurement values, said adaptive digital filter operating on said stream of measurement values according to said set of digital filter values during a measurement phase to provide normalized measurement values with the effects of said frequency response substantially reduced.