Soft quantizer for FM radio binary digital signaling
First Claim
1. A soft quantizer for converting a demodulated signal, including recovered digital data and an analog noise signal, from a discriminator output of a digital receiver employing non-linear demodulation, to soft quantized digital values reflecting the numerical weight of the decoded digital data, based upon the noise energy of the received demodulated signal, comprising:
- digital detector means to convert the recovered digital data from the discriminator to hard quantized digital data on a detector output line;
analog to digital converter means for filtering the analog noise signal from the recovered digital data, converting the analog noise signal to a digital representation and supplying said digital representation as an output signal;
addressable memory means having a plurality of addressable locations and from which previously stored predetermined numerical weights may be retrieved from one of the addressable locations as selected by the digital output signal from the analog to digital converter means; and
combiner means for combining the hard quantized digital data from the output of the digital detector with the numerical weights read from said addressable memory means to generate a soft quantized digital value reflecting the numerical weight of the detected data, based upon the level of the noise energy in the digital receiver.
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Abstract
A soft quantizer for assigning numerical weights to hard quantized output bits of a binary digital detector in a digital receiver based on the noise energy level of the received baseband data. An analog signal, derived from the discriminator noise level, is digitized by an analog to digital converter for use as an address to look up predetermined numerical weights for soft quantized values in a memory table. The addressed numerical weights are combined with the hard quantized output bits of the digital detector to generate soft quantized data values.
58 Citations
8 Claims
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1. A soft quantizer for converting a demodulated signal, including recovered digital data and an analog noise signal, from a discriminator output of a digital receiver employing non-linear demodulation, to soft quantized digital values reflecting the numerical weight of the decoded digital data, based upon the noise energy of the received demodulated signal, comprising:
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digital detector means to convert the recovered digital data from the discriminator to hard quantized digital data on a detector output line; analog to digital converter means for filtering the analog noise signal from the recovered digital data, converting the analog noise signal to a digital representation and supplying said digital representation as an output signal; addressable memory means having a plurality of addressable locations and from which previously stored predetermined numerical weights may be retrieved from one of the addressable locations as selected by the digital output signal from the analog to digital converter means; and combiner means for combining the hard quantized digital data from the output of the digital detector with the numerical weights read from said addressable memory means to generate a soft quantized digital value reflecting the numerical weight of the detected data, based upon the level of the noise energy in the digital receiver. - View Dependent Claims (2, 3, 4, 5)
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6. A method of generating a soft quantized digital data value based upon the noise energy of the received demodulated signal at a discriminator output of a digital receiver, said method comprising the steps of;
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converting the received demodulated signal from the discriminator output to hard quantized digital data; filtering the output of the discriminator to obtain an analog noise signal from the received demodulated signal; converting the analog noise signal to a digital representation; addressing a predetermined table of numerical weights by using said digital representation of the noise signal; and combining the addressed numerical weights with the hard quantized data values from the digital detector means to generate a soft quantized data output value based upon the analog noise signal and the recovered digital data in the demodulated signal. - View Dependent Claims (7)
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8. The method of step 6 wherein the digital detector output is a one bit binary number, and the step of combining the addressed numerical weights with the digital detector output consists of appending the digital detector bit as a sign bit, whereby a sign plus magnitude soft quantized value is obtained.
Specification