Adaptive RFID receiver for QAM signals
First Claim
1. In a base-band receiver, a method for coherently tracking and decoding a received 16-QAM encoded data signal comprising a plurality of data symbols, the method comprising:
- (a) demodulating the received 16-QAM encoded data signal to generate an in-phase component and a quadrature-phase component of the encoded data signal;
(b) integrating the in-phase component during each data symbol interval;
(c) integrating the quadrature-phase component during each data symbol interval;
(d) combining results of the integrations in (b) and (c) to generate a received signal vector, wherein coordinates of the received signal vector represent the in-phase and quadrature-phase component, respectively, of the received encoded 16-QAM data signal;
(e) correcting the received signal vector according to a correction algorithm by modifying the coordinates of the received signal vector with coordinates of a current reference signal vector to generate a corrected received signal vector;
(f) determining a decision index and a decoded binary value for each of the plurality of data symbols corresponding to one of 16 constellation points arranged in a 4×
4 square array in a constellation diagram with 16 predetermined states, according to a decision-making algorithm using the corrected received signal vector;
(g) transforming the received signal vector according to a tracking algorithm using the decision index to generate a transformed received signal vector; and
(h) updating the coordinates of the current reference signal vector using computed values of the transformed received signal vector averaged over a predetermined sequence of data symbols.
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Abstract
The present invention provides methods and apparatuses for demodulation and decoding of backscattered 16-QAM RFID tag signals, represented by their in-phase and quadrature components at the output of the demodulator in the receiver portion of a reader interrogator. In a communication channel with fast changing parameters, a reader receiver adaptively and coherently corrects the in-phase and quadrature-phase components of a signal received from a tag by tracking the phase and amplitude of the signal based on a decision-feedback. A reference signal is used to correct the signal components, where the coordinates of the reference signal is updated by a tracking and an averaging algorithm. A simple implementation of the receiver in a digital signal processing environment is enabled.
20 Citations
27 Claims
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1. In a base-band receiver, a method for coherently tracking and decoding a received 16-QAM encoded data signal comprising a plurality of data symbols, the method comprising:
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(a) demodulating the received 16-QAM encoded data signal to generate an in-phase component and a quadrature-phase component of the encoded data signal; (b) integrating the in-phase component during each data symbol interval; (c) integrating the quadrature-phase component during each data symbol interval; (d) combining results of the integrations in (b) and (c) to generate a received signal vector, wherein coordinates of the received signal vector represent the in-phase and quadrature-phase component, respectively, of the received encoded 16-QAM data signal; (e) correcting the received signal vector according to a correction algorithm by modifying the coordinates of the received signal vector with coordinates of a current reference signal vector to generate a corrected received signal vector; (f) determining a decision index and a decoded binary value for each of the plurality of data symbols corresponding to one of 16 constellation points arranged in a 4×
4 square array in a constellation diagram with 16 predetermined states, according to a decision-making algorithm using the corrected received signal vector;(g) transforming the received signal vector according to a tracking algorithm using the decision index to generate a transformed received signal vector; and (h) updating the coordinates of the current reference signal vector using computed values of the transformed received signal vector averaged over a predetermined sequence of data symbols. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A base-band receiver configured to coherently track and decode a 16-QAM encoded data signal comprising a plurality of data symbols, the receiver comprising:
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a local oscillator that locally alters a frequency of the encoded data signal for subsequent processing; a demodulator that demodulates the encoded data signal into an in-phase component and a quadrature-phase component; a first integrator that receives the in-phase component of the encoded data signal and generates a real coordinate of a received signal vector by integrating the in-phase component during a data symbol interval; a second integrator that receives the quadrature-phase component of the encoded data signal and generates an imaginary coordinate of the received signal vector by integrating the quadrature-phase component during the data symbol interval; a correction module that receives the received signal vector and a reference signal vector, and corrects the received signal vector according to a correction algorithm modifying the coordinates of the received signal vector with coordinates of a reference signal vector to generate a corrected received signal vector; a decision module that receives the corrected received signal vector and determines a decision index and a decoded binary value for each data symbol corresponding to one of 16 constellation points arranged in a 4×
4 square array in a constellation diagram with 16 predetermined states, according to a decision-making algorithm using the corrected received signal vector;an estimating module that receives the received signal vector and the decision index determined by the decision module, and transforms the received signal vector according to a tracking algorithm using the decision index to generate a transformed received signal vector; and an averaging module that receives the transformed received signal vector and outputs an updated reference signal vector by updating the coordinates of the current reference signal vector using computed values of the transformed received signal vector averaged over a predetermined sequence of data symbols. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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25. In a base-band receiver, a method for coherently tracking and decoding a m-QAM encoded data signal comprising a plurality of data symbols, wherein the encoded data signal is demodulated into an in-phase component and a quadrature-phase component, the tracking and decoding method comprising:
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integrating the in-phase component and the quadrature-phase component during each data symbol interval; combining results of the in-phase component integration and the quadrature-phase component integration to generate a received signal vector, wherein coordinates of the received signal vector represent the in-phase and quadrature-phase component, respectively, of the received encoded m-QAM data signal; correcting the received signal vector according to a correction algorithm by modifying the coordinates of the received signal vector with coordinates of a current reference signal vector to generate a corrected received signal vector; determining a decision index and a decoded binary value for each of the plurality of data symbols corresponding to one of m constellation points arranged in a n by n square array in a constellation diagram with m predetermined states, according to a decision-making algorithm using the corrected received signal vector; transforming the received signal vector according to a tracking algorithm using the decision index to generate a transformed received signal vector; and updating the coordinates of the current reference signal vector using computed values of the transformed received signal vector averaged over a predetermined sequence of data symbols.
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26. A base-band receiver configured to coherently track and decode a m-QAM encoded data signal comprising a plurality of data symbols, wherein the encoded data signal is demodulated into an in-phase component and a quadrature-phase component, the receiver comprising:
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a first integrator that receives the in-phase component of the encoded data signal and generates a real coordinate of a received signal vector by integrating the in-phase component during a data symbol interval; a second integrator that receives the quadrature-phase component of the encoded data signal and generates an imaginary coordinate of the received signal vector by integrating the quadrature-phase component during the data symbol interval; a correction module that receives the received signal vector and a reference signal vector, and corrects the received signal vector according to a correction algorithm modifying the coordinates of the received signal vector with coordinates of a reference signal vector to generate a corrected received signal vector; a decision module that receives the corrected received signal vector and determines a decision index and a decoded binary value for each data symbol corresponding to one of m constellation points arranged in a n by n square array in a constellation diagram with m predetermined states, according to a decision-making algorithm using the corrected received signal vector; an estimating module that receives the received signal vector and the decision index determined by the decision module, and transforms the received signal vector according to a tracking algorithm using the decision index to generate a transformed received signal vector; and an averaging module that receives the transformed received signal vector and outputs an updated reference signal vector by updating the coordinates of the current reference signal vector using computed values of the transformed received signal vector averaged over a predetermined sequence of data symbols.
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27. In a base-band receiver, a system for coherently tracking and decoding a m-QAM encoded data signal comprising a plurality of data symbols, wherein the encoded data signal is demodulated into an in-phase component and a quadrature-phase component, the tracking and decoding system comprising:
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means for integrating the in-phase component and the quadrature-phase component during each data symbol interval; means for combining results of the in-phase component integration and quadrature-phase component integration to generate a received signal vector, wherein coordinates of the received signal vector represent the in-phase and quadrature-phase component, respectively, of the received encoded m-QAM data signal; means for correcting the received signal vector according to a correction algorithm by modifying the coordinates of the received signal vector with coordinates of a current reference signal vector to generate a corrected received signal vector; means for determining a decision index and a decoded binary value for each of the plurality of data symbols corresponding to one of m constellation points arranged in a n by n square array in a constellation diagram with m predetermined states, according to a decision-making algorithm using the corrected received signal vector; means for transforming the received signal vector according to a tracking algorithm using the decision index to generate a transformed received signal vector; and means for updating the coordinates of the current reference signal vector using computed values of the transformed received signal vector averaged over a predetermined sequence of data symbols.
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Specification