Data demodulation
First Claim
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1. A data demodulating method in which binary data are defined by two-frequency encoded signal composed of a combination of high and low frequency signals, binary data for one character are defined by a predetermined number of said binary data and a parity bit, peak points are detected in a reproduced signal waveform obtained by reproducing a recorded data signal to demodulate said binary data, comprising the steps of:
- preparing in advance a reference line pattern for each character, composed of peak interval values of bits that constitute one character;
measuring time intervals between successive peaks of said reproduced signal; and
comparing each of said peak interval values that constitute one character with said reference line patterns by a pattern matching to determine the character corresponding to said reference line pattern having the highest degree of similarity as the character.
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Abstract
The accuracy of demodulation of data from a magnetic stripe is enhanced by comparing time intervals between successive peaks of each character of the signal read from the stripe against a set of predetermined reference successive peak time intervals for the data characters.
97 Citations
11 Claims
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1. A data demodulating method in which binary data are defined by two-frequency encoded signal composed of a combination of high and low frequency signals, binary data for one character are defined by a predetermined number of said binary data and a parity bit, peak points are detected in a reproduced signal waveform obtained by reproducing a recorded data signal to demodulate said binary data, comprising the steps of:
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preparing in advance a reference line pattern for each character, composed of peak interval values of bits that constitute one character;
measuring time intervals between successive peaks of said reproduced signal; and
comparing each of said peak interval values that constitute one character with said reference line patterns by a pattern matching to determine the character corresponding to said reference line pattern having the highest degree of similarity as the character. - View Dependent Claims (2, 3, 4, 5)
converting said reproduced signal waveform to a digital signal by an AD conversion;
measuring time intervals between successive peaks of said digitized reproduced signal to create a peak interval value line;
determining the end of one character by successively adding each of peak interval values of said peak interval value line; and
comparing each of said peak interval values that constitute one character with said reference line patterns.
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4. The data demodulating method as set forth in claim 3, further comprising steps of:
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predetermining a character time interval for one character of said recorded data by a predetermined number of bits in a given range;
determining said end of one character based on a peak position within said character time interval for one character;
detecting if the number of peak interval values up to said peak position within said character time interval satisfies the characteristic condition of parity bit;
when said condition is not satisfied, adding the next peak interval value to determine the end of one character.
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5. The data demodulating method as set forth in claim 1 wherein time intervals of said reference line patterns are expressed by binary numbers based on the length of said time intervals, and a pattern matching is performed to compare said peak interval values of said reproduced signal with said reference line patterns expressed by binary numbers.
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6. A data demodulating method in which binary data are defined by a two-frequency encoded signal composed of a combination of high and low frequencies, data for one character are produced with a predetermined number of said binary data and a parity bit, and peak points of a reproduced signal waveform obtained by reproducing a recorded data are detected to read said binary data, comprising steps of:
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measuring peak time intervals between successive peaks of said reproduced signal waveform;
comparing each of said peak interval values that constitute one character with a reference value to convert said signal waveform to a bit line composed of said binary data;
for demodulating data of one character, selecting a plurality of segment length candidates for demodulation, on the basis of a reference segment length equal to a data interval for one character and peak positions; and
performing pattern matching on a plurality of said segment length candidates with reference waveform data to determine the character according to the similarity. - View Dependent Claims (7, 8, 9, 10)
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11. A data demodulating apparatus in which binary data are defined by a two-frequency encoded signal composed of a combination of high and low frequencies, data for one character are produced with a predetermined number of said binary data, and peak points of a reproduced signal waveform obtained by reproducing a recorded data are detected to read said binary data, comprising:
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a means of measuring peak time intervals between successive peaks of said reproduced signal waveform;
a means of demodulating data for one character by comparing each of said peak interval values that constitute one character with a reference value to convert said signal waveform to a bit line composed of said binary data; and
for demodulating data of one character, a means of determining the character, wherein a plurality of segment length candidates for demodulation are selected on the basis of a reference segment length equal to a data interval for one character and peak positions;
pattern matching is performed on a plurality of said segment length candidates with reference waveform data to determine the character according to the similarity.
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Specification