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Abstract

A digital demodulator provides efficient demodulation of frequency modulated, pulse-width modulated, and other temporally modulated signals. Without employing an analog-to-digital converter, modulating signal information is extracted from a modulated signal as numerical information. For frequency demodulation, a high gain stage is applied to an incoming FM signal to produce a corresponding sequence of square waves. The period between zero-crossings of the square waves is accurately measured to within one clock pulse using a high-speed clock and at least one counter. Period information is then provided to a signal processor that serves to convert the sequence of period measurement values into a demodulated signal with a high signal-to-noise ratio. In another embodiment, a so-termed 'reciprocal fit count scaling' method is employed to provide an exact analytic solution to count scaling performed in the signal processor, and thus provide the most accurate and optimal results attainable from a system of this type. Such improved performance provides an estimated signal with significantly high scaling accuracy, lower total harmonic distortion, and an excellent signal-to-noise ratio.

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First Claim