Demodulator system and method
First Claim
Patent Images
1. A demodulator system comprising:
- an analog-to-digital converter (ADC) configured to sample a modulated signal and to output a digital signal;
a Coordinate Rotation Digital Computer (CORDIC) mixer coupled to an output of the ADC, the CORDIC mixer to generate an Inphase (I) signal and a Quadrature (Q) signal based on the digital signal output by the ADC and further based on an input frequency;
a filter path to process the I signal and the Q signal generated by the CORDIC mixer, wherein the filter path is coupled to at least one decimator;
a demodulation stage to demodulate an output of the filter path, wherein the demodulation stage includes a CORDIC demodulator; and
a symbol decoder to receive a phase signal from the CORDIC demodulator, the symbol decoder including symbol recognition logic to adjust a sample of the phase signal by an offset value, to map the adjusted sample to a nearest predetermined phase value of a plurality of predetermined phase values, and to determine a symbol using a difference between the nearest predetermined phase value and a prior nearest predetermined phase value, wherein the offset value at least partially compensates for a phase drift generated at the CORDIC mixer.
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Abstract
A demodulator system and method is disclosed. In an embodiment, the demodulator system can include a Coordinate Rotation Digital Computer (CORDIC) mixer to mix a first signal substantially to baseband using a first input frequency and to mix a second signal substantially to baseband using a second input frequency. In another embodiment, the demodulator system can include a phase detector to receive a pilot signal and to generate a control signal to adjust a decimation rate based on the pilot signal. In another embodiment, the demodulator system can include a symbol decoder to determine a symbol from a phase signal.
54 Citations
29 Claims
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1. A demodulator system comprising:
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an analog-to-digital converter (ADC) configured to sample a modulated signal and to output a digital signal; a Coordinate Rotation Digital Computer (CORDIC) mixer coupled to an output of the ADC, the CORDIC mixer to generate an Inphase (I) signal and a Quadrature (Q) signal based on the digital signal output by the ADC and further based on an input frequency; a filter path to process the I signal and the Q signal generated by the CORDIC mixer, wherein the filter path is coupled to at least one decimator; a demodulation stage to demodulate an output of the filter path, wherein the demodulation stage includes a CORDIC demodulator; and a symbol decoder to receive a phase signal from the CORDIC demodulator, the symbol decoder including symbol recognition logic to adjust a sample of the phase signal by an offset value, to map the adjusted sample to a nearest predetermined phase value of a plurality of predetermined phase values, and to determine a symbol using a difference between the nearest predetermined phase value and a prior nearest predetermined phase value, wherein the offset value at least partially compensates for a phase drift generated at the CORDIC mixer. - View Dependent Claims (2, 3, 4, 5)
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6. A demodulator system comprising:
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a Coordinate Rotation Digital Computer (CORDIC) mixer to receive a first input signal modulated using a first modulation mode and to generate a first Inphase (I) signal and a first Quadrature (Q) signal by mixing the first input signal substantially to baseband using a first input frequency, the CORDIC mixer further to receive a second input signal modulated using a second modulation mode and to generate a second I signal and a second Q signal by mixing the second input signal substantially to baseband using a second input frequency; a filter path to process an output of the CORDIC mixer, wherein the filter path is coupled to at least one decimator; a demodulation stage to demodulate an output of the filter path, wherein the demodulation stage includes a CORDIC demodulator; and a symbol decoder to receive a phase signal from the CORDIC demodulator, the symbol decoder including symbol recognition logic to adjust a sample of the phase signal by an offset value, to map the adjusted sample to a nearest predetermined phase value of a plurality of predetermined phase values, and to determine a symbol using a difference between the nearest predetermined phase value and a prior nearest predetermined phase value, wherein the offset value at least partially compensates for a phase drift generated at the CORDIC mixer. - View Dependent Claims (7)
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8. A demodulator system comprising:
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a Coordinate Rotation Digital Computer (CORDIC) mixer to generate an Inphase (I) signal and a Quadrature (Q) signal based on a modulated input signal and an input frequency; a decimator to perform decimation of the I signal and the Q signal at an adjustable decimation rate; a phase detector to receive a pilot signal and including decimation rate logic to generate a control signal to adjust the decimation rate based on the pilot signal; and a demodulation stage to demodulate a filtered output of the decimator, wherein the demodulation stage includes a CORDIC demodulator. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16)
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17. A demodulator system comprising:
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a Coordinate Rotation Digital Computer (CORDIC) mixer to generate an Inphase (I) signal and a Quadrature (Q) signal; a decimator coupled to the CORDIC mixer to adjust a sample rate of at least one of the I signal and the Q signal; a filter path coupled to the decimator to process an output of the decimator; a demodulation stage to demodulate an output of the filter path, wherein the demodulation stage includes a CORDIC demodulator, and a symbol decoder to receive a phase signal from the CORDIC demodulator, the symbol decoder including symbol recognition logic to adjust a sample of the phase signal by an offset value, to map the adjusted sample to a nearest predetermined phase value of a plurality of predetermined phase values, and to determine a symbol using a difference between the nearest predetermined phase value and a prior nearest predetermined phase value, wherein the offset value at least partially compensates for a phase drift generated at the CORDIC mixer. - View Dependent Claims (18, 19, 20, 21)
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22. A demodulation method comprising:
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receiving a modulated signal; mixing an audio signal substantially to baseband with a Coordinate Rotation Digital Computer (CORDIC) mixer having multiple pipelined mixing stages; decimating an output of the CORDIC mixer with a decimator having an adjustable decimation rate; demodulating a filtered output of the decimator with a CORDIC demodulator; and receiving a phase signal from the CORDIC demodulator at a symbol decoder, the symbol decoder including symbol recognition logic to adjust a sample of the phase signal by an offset value, to map the adjusted sample to a nearest predetermined phase value of a plurality of predetermined phase values, and to determine a symbol using a difference between the nearest predetermined phase value and a prior nearest predetermined phase value, wherein the offset value at least partially compensates for a phase drift generated at the CORDIC mixer. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29)
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Specification