Error correcting code decoder
First Claim
1. A coded signal decoder comprising:
- (a) first means for concatenating a cyclic block coded input signal, having a period of a predetermined codeword, with itself,(b) a first filter matched to a first predetermined code sequence of said signal connected to receive the concatenated signal,(c) a first peak position decoder connected to receive an output signal from the matched filter for providing an indication of the position of an autocorrelation peak corresponding to said code sequence relative to the input signal code, whereby the particular code is designated.
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Accused Products
Abstract
A method and apparatus which can significantly reduce the matched filter requirements in decoding cyclic block codes, and is particularly advantageous for decoding maximal length block codes, and other cyclic block codes in which the number of codewords is ≦2k where k is the number of data bits encoded into each codeword. The signal containing the codeword is concatenated with itself, then the concatenated signal is applied to a matched filter to provide a peaking signal at some point in time as the concatenated signal is passed through the matched filter. The position of the peaking signal relative to a predetermined instant of time is sensed whereby the identity of the codeword (and thus data) can be determined.
48 Citations
36 Claims
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1. A coded signal decoder comprising:
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(a) first means for concatenating a cyclic block coded input signal, having a period of a predetermined codeword, with itself, (b) a first filter matched to a first predetermined code sequence of said signal connected to receive the concatenated signal, (c) a first peak position decoder connected to receive an output signal from the matched filter for providing an indication of the position of an autocorrelation peak corresponding to said code sequence relative to the input signal code, whereby the particular code is designated. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 35)
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16. A method of decoding a cyclic block code containing a predetermined codeword comprising:
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(a) concatenating a signal containing the codeword with itself, (b) applying the concatenated signal to a matched filter, to provide a peaking signal when a section of the concatenated signal one codeword duration matches the filter, (c) sensing the position of the peaking signal relative to a predetermined instant in time whereby the identity of the codeword and thus data can be determined. - View Dependent Claims (17)
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18. A decoder comprising:
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(a) means for providing a correlation signal representing a cyclic correlation of an input signal with a signal representing a predetermined codeword, (b) means for determining the position of an autocorrelation peak resulting from said correlation signal, and (c) means responsive to the position determining means for indicating the presence of said predetermined codeword upon said peak being in a predetermined position. - View Dependent Claims (19, 20, 21, 22, 23)
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24. A decoder for determining the synchronization of an input signal comprised of a correlatable cyclically shifted codeword once concatenated with itself followed by at least one information bearing codeword comprising:
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(a) means for providing a sample of the received input signal starting at or after the beginning of the concatenated code word sequence and ending before or at the end of the concatenated codeword sequence, the sample having the length of the codeword, (b) first correlating means for correlating the sample with a sample of the codeword to provide a correlation signal, (c) first means for determining the position of the autocorrelation peak, whereby the position of said peak relative to the end of the concatenated sequence indicates the time prior to the start of the information bearing codeword. - View Dependent Claims (32, 33, 34, 36)
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25. A decoder for determining the synchronization of an input signal comprised of an m sequence code once concatenated with itself followed by at least one information bearing codeword comprising:
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(a) means for providing an m length sample of the received input signal starting at or after the beginning of the m sequence and ending before or at the end of the concatenated code, (b) first and second multipliers for multiplying the sample with first sine and cosine waveform signals respectively, the latter signals having the frequency of a carrier of the input signal, (c) first and second correlating means for providing correlation signals representing the cyclic correlation of output signals of the first and second multipliers respectively with a signal representing a predetermined codeword, (d) means for providing a signal representing the arctangent of the output signals of the first and second correlating means, whereby said latter signal representing the magnitude of the cyclic autocorrelation function is obtained at a peak position corresponding to the phase of the m sequence sample signal relative to the information bearing codeword. - View Dependent Claims (26, 27, 28, 29)
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30. A decoder for determining the synchronization of an input signal comprised of a correlatable cyclically shifted codeword once concatenated with itself followed by at least one information bearing codeword comprising:
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(a) means for repeatedly providing a sample of the received input signal starting before the arrival of the concatenated codeword sequence and ending before or at the end of the concatenated codeword sequence, the sample having the length of the codeword, (b) first correlating means for repeatedly correlating the sample with a sample of the codeword to provide a correlation signal, (c) first means for determining the position of the autocorrelation peak, whereby the position of said peak relative to the end of the concatenated sequence indicates the time prior to the start of the information bearing codeword.
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31. A decoder for determining the synchronization of an input signal comprised of an m sequence code once concatenated with itself followed by at least one information bearing codeword comprising:
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(a) means for repeatedly providing an m length sample of the received input signal starting before the arrival of the first m sequence codeword and ending before or at the end of the concatenated codeword, (b) first and second multipliers for multiplying the same with first sine and cosine waveform signals respectively, the latter signals having the frequency of a carrier of the input signal, (c) first and second correlating means for providing correlation signals representing the cyclic correlation of the output signals of the first and second multipliers respectively with a signal representing a predetermined codeword, (d) means for providing a signal representing the square of the output signals of the first and second correlating means, whereby said latter signal representing the magnitude of the cyclic autocorrelation function is obtained at a peak position corresponding to the phase of the m sequence sample signal relative to the information bearing codeword.
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Specification