One-bit codec with slope overload correction
AssigneeBell Telephone Laboratories, Incorporated
InventorO'Connell J. Benjamin
Life of this patent
Estimating the term…
Abstract
In a delta modulation coder and decoder system, the disadvantageous effects of slope overload are eliminated by reversing the polarity of the feedback signal in the coder and the polarity of the reconstructed analog signal in the decoder whenever slope overload correction is required. This is accomplished by the addition, to both the coder and decoder, of control circuitry which determines whether slope overload correction is required. To make the determination, first the digital output signal of the coder is tested to determine whether its rate of change is equal to a maximum value. Second, the magnitude of the feedback signal is tested to see if it lies below a threshold value. If both these conditions are satisfied, slope overload correction is then performed.
Claims23
A method for compensating for slope overload in a differential digital pulse code system comprising the steps of:
- combining an analog input signal with a reconstructed signal to generate an error signal,
- sampling the error signal to produce a digital signal,
- generating said reconstructed signal in response to said digital signal,
- detecting an occurrence of slope overload, and
- reversing the polarity of said reconstructed signal when such occurrence of slope overload is detected.
A coder, which corrects for slope overload comprising
- means for combining an analog input signal and a reconstructed analog signal to form an error signal,
- means for sampling the error signal to produce a digital signal,
- means for generating said reconstructed analog signal in response to said digital signal, and
- means for detecting an occurrence of slope overload
- characterized in that
- said generating means further includes means for reversing the polarity of said reconstructed analog signal in response to an occurrence of slope overload.
In an arrangement, for processing a digital signal derived from the difference between an analog input signal and an analog signal which approximates the analog input signal from a prior time interval,
- means for reconstructing an analog signal from said digital signal
- characterized in that
- said reconstructing means further includes means for reversing the polarity of said reconstructed analog signal in response to a slope overload condition.
Dependencies are inferred from the claim text.