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US 5,907,528 AGranted
Apparatus for demodulating a digital FM signal which normally has signal inversions at data bit boundaries
AssigneeSony Corporation
InventorYoshiro Joichi
Life of this patent
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Abstract
In a demodulator for a digital FM signal, the received digital FM signal is verified at the data bit boundaries for inversion to detect errors. If an uninverted data bit boundary is detected, those sections of the digital FM signal just preceding and just following the uninverted data bit boundary are modified thereby generating two modified signals. Using the error detecting code included in the digital FM signal, the two modified signals are evaluated to determine which modification corrects the errors and the modified signal with the correct modification is selected.
Claims9
Apparatus for demodulating a digital FM signal which contains error correcting code and normally has signal level inversions at data bit boundaries, comprising:
- means for receiving said digital FM signal;
- means for detecting the existence or nonexistance of signal level inversions of said digital FM signal at respective data bit boundaries so as to indicate errors in said digital FM signal in response to said nonexistance of signal level inversions;
- means for modifying the signal level of said digital FM signal just before and just after a data bit boundary at which nonexistance of signal level inversion has been detected so as to provide first and second modified digital FM signals, respectively;
- means for evaluating said first and second modified digital FM signals using said error detecting code included in said digital FM signal so as to determine which of said first and second modified digital FM signals corrects a respective one of said errors in said digital FM signal;
- means for selecting said modified digital FM signal which corrects said respective one of said errors;
- and
- means for correcting said digital FM signal in accordance with said modified digital FM signal selected by said means for selecting.
4 more elements
Apparatus for demodulating a digital FM signal which contains error correcting code and normally has signal level inversions at data bit boundaries, comprising:
- means for receiving said digital FM signal;
- means for detecting the existence or nonexistance of signal level inversions of said digital FM signal at respective data bit boundaries so as to indicate errors in said digital FM signal in response to said nonexistence of signal level inversions;
- means for modifying the signal level of said digital FM signal just before and just after a data bit boundary at which nonexistance of signal level inversion has been detected so as to provide first and second modified digital FM signals, respectively;
- means for evaluating said first and second modified digital FM signals using said error detecting code included in said digital FM signal so as to determine which of said first and second modified digital FM signals corrects a respective one of said errors in said digital FM signal;
- means for selecting said modified digital FM signal which corrects said respective one of said errors;
- and
- means for correcting said digital FM signal in accordance with said modified digital FM signal selected by said means for selecting;
- wherein said means for modifying comprises means for delaying said digital FM signal by one clock pulse of a first clock signal to provide a first delayed signal, means for combining said digital FM signal and said first delayed signal to provide a first combined signal, means for delaying said first combined signal by one clock pulse of said first clock signal to provide a second delayed signal, means for combining said first combined signal and said second delayed signal to provide a second combined signal, and means for generating a demodulated signal from said second combined signal in synchronism with a second clock signal.
5 more elements
A method of demodulating a digital FM signal which contains error correcting code and normally has signal level inversions at data bit boundaries, comprising the steps of:
- receiving said digital FM signal;
- detecting the existence or nonexistance of signal level inversions of said digital FM signal at respective data bit boundaries so as to indicate errors in said digital FM signals in response to said nonexistance of signal level inversions;
- modifying the signal level of said digital FM signal just before and just after a data bit boundary at which nonexistance of signal level inversion has been detected so as to provide first and second modified digital FM signals, respectively;
- evaluating said first and second modified digital FM signals using said error detecting code included in said digital FM signal so as to determine which of said first and second modified digital FM signals corrects a respective one of said errors in said digital FM signal;
- selecting said modified digital FM signal which corrects the respective one of said errors;
- and
- correcting said digital FM signal in accordance with the selected modified digital FM signal;
- wherein the step of modifying comprises delaying said digital FM signal by one clock pulse of a first clock signal to provide a first delayed signal, combining said digital FM signal and said first delayed signal to provide a first combined signal, delaying said first combined signal by one clock pulse of said first clock signal to provide a second delayed signal, combining said first combined signal and said second delayed signal to provide a second combined signal, and generating a demodulated signal from said second combined signal in synchronism with a second clock signal.
5 more elements
A method of demodulating a digital FM signal which contains error correcting code and normally has signal level inversions at data bit boundaries, comprising the steps of:
- receiving said digital FM signal;
- detecting the existence or nonexistance of signal level inversions of said digital FM signal at respective data bit boundaries so as to indicate errors in said digital FM signals in response to said nonexistance of signal level inversions;
- modifying the signal level of said digital FM signal just before and just after a data bit boundary at which nonexistance of signal level inversion has been detected so as to provide first and second modified digital FM signals, respectively;
- evaluating said first and second modified digital FM signals using said error detecting code included in said digital FM signal so as to determine which of said first and second modified digital FM signals corrects a respective one of said errors in said digital FM signal;
- selecting said modified digital FM signal which corrects the respective one of said errors;
- and
- correcting said digital FM signal in accordance with the selected modified digital FM signal.
4 more elements
Dependencies are inferred from the claim text.