Digital envelope detector
AssigneeThe United States of America as represented by the Secretary of the Navy
InventorRichard A. Kant
Life of this patent
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Abstract
A digital envelope detector (consisting of both hardware and software) that provides accurate measurements of changes of peak values of an AC signal (these peak values constitute the envelope of a signal). Such accurate envelope measurements are required to optimize the accuracy and selectivity of chemical sensors. A signal of interest is compared to each of a set of accurately calibrated reference voltages provided by a digital to analog converter. A digital logic circuit and software respond each time the signal fails to exceed the current reference voltage. In that event, relevant data (time or cycle count) are digitally recorded and a new reference voltage is installed. The process is repeated until the desired range of change of signal is measured.
Claims1
A process for digitally detecting a decay envelope of an AC signal in a mechanical loss spectrometer, comprised of:
- selecting a first or highest reference voltage;
- setting interrupt service routine active flat set drive OFF
- interrupting RAM resident routine during ringdown;
- waiting for the end of ringdown measurement;
- switching drive OFF;
- retrieving counter and frequency data;
- calculating least squares fit to decay envelope;
- adjusting drive frequency using measured data;
- adjusting temperature controls;
- recording time, loss, frequency, and temperature data;
- adjusting drive for acceptable response signal amplitude;
- executing search for position of peak if signal is set out of range;
- and
- repeating main loop for next or second highest reference voltage.
Dependencies are inferred from the claim text.