FM Signal demodulator
First Claim
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1. A method for demodulating an FM signal consisting of at least first and second discrete frequency components f0 and f1 representing data values and for deriving an output signal containing said data comprising the steps of:
- sampling the FM signal periodically and at a rate higher than the rate of occurrence of said components;
counting the number of excursions n of said signal during each sample time;
comparing the sample counts n to a number N which is higher than the maximum number of f0 excursions which occur during a sample time and which is lower than the maximum number of f1 excursions which occur during a sample time; and
generating an output having a first characteristic when n is less than N and a second characteristic when n is greater than N.
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Abstract
An FM demodulator wherein the input signal excursions advance a counter. At each of a sequence of equal sample times, the count is compared to a value which is the average of the highest and lowest counts during the sequence. The comparison may be numerically direct or by down-counting from a present number. The result of the comparison sets an output data value either "1" or "0".
56 Citations
6 Claims
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1. A method for demodulating an FM signal consisting of at least first and second discrete frequency components f0 and f1 representing data values and for deriving an output signal containing said data comprising the steps of:
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sampling the FM signal periodically and at a rate higher than the rate of occurrence of said components; counting the number of excursions n of said signal during each sample time; comparing the sample counts n to a number N which is higher than the maximum number of f0 excursions which occur during a sample time and which is lower than the maximum number of f1 excursions which occur during a sample time; and generating an output having a first characteristic when n is less than N and a second characteristic when n is greater than N. - View Dependent Claims (2, 3)
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4. An FM signal demodulator for deriving a data signal from an FM signal consisting of first and second distinct frequency components f0 and f1 comprising:
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means for sampling the FM signal periodically and at a rate higher than the rate of occurrence of said components within said FM signal; means for counting the number of excursions n of said signal during each sample time; means for comparing a sample count to a number N which is higher than the maximum number of f0 excursions which occur during a sample time and which is lower than the maximum number of f1 excursions which occur during a sample time; and means for generating an output having a first characteristic when n is less than N and a second characteristic when n is greater than N. - View Dependent Claims (5, 6)
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Specification