Compensation for non-linear distortion in a modem receiver
AssigneeBroadband Physics, Inc.
InventorWilliam J. Miller
Life of this patent
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Abstract
A method and modem receiver for receiving serial data from a transmission link, for recovering data from the received data, and for synchronizing the receiver timing to that of the transmitter are disclosed. A receiver equalizer includes a filter and quantizer in the forward path and a feedback circuit connecting the quantizer output to the filter input. A measuring circuit is used to initialize the feedback circuit. The receiver filter, provided as a QMF wavelet filter bank, is implemented in one embodiment with a form of polyphase filtering followed by four M/2-point FFTs. The quantizer recovers data symbols and provides a quantization error feedback signal. The measuring circuit provides an approximation of phase and amplitude of isolated wavelets.
Claims41
A multi-band equalizer for a modem receiver, comprising:
- a self-interference canceling filter for receiving an input signal, for removing from the input signal cross correlation terms resulting from input signal self-interference and for providing a corrected input signal, the self-interference canceling filter comprising
- a fixed tap-weight filter bank for filtering the input signal,
- a weighting circuit for weighting the filtered input signal with a pre-determined function of a differential phase angle between adjacent subbands of the input signal, and
- a subtraction circuit for subtracting the weighted, filtered input signal from the input signal to generate the corrected input signal;
- a quantizer for quantizing the corrected input signal and for providing a quantizer error signal based upon a difference between the corrected input signal and the quantized, corrected input signal;
- and
- a feedback circuit for calculating a proportional phase correction metric from the quantizer error signal and for providing phase values for plural subbands, derived from the proportional phase correction metric, to the self-interference canceling filter.
A multi-band equalizer for a modem receiver, comprising:
- a quantizer for receiving an input signal, for quantizing the input signal, and for providing a quantizer error signal based upon the difference between the input signal and the quantized input signal;
- and
- an amplitude measurement loop for multiplying the quantizer error signal by a value inversely proportional to the quantized input signal and for providing a product of the multiplication as a gain error offset value;
- an amplitude measurement unit for receiving the gain error offset value from the amplitude measurement loop and for deriving a gain factor therefrom;
- and
- a multiplier for multiplying the input signal by the gain factor prior to quantization of the input signal by the quantizer.
A method of processing input data in a multi-band equalizer to realize recovered data, comprising:
- filtering the input data in a filter to remove self-interference cross correlation terms from the input signal resulting from self-interference and to provide phase and time delay corrected input data by
- filtering the input data using a fixed tap-weight filter bank,
- weighting the filtered data using a predetermined function of a differential phase angle between adjacent subbands of the input data, and
- subtracting the weighted, filtered input data from the input data to generate the phase and time delay corrected input data;
- quantizing the corrected input data by a quantizer and providing a quantizer error signal as the difference between the corrected input data and the quantized, corrected input data;
- and
- calculating a proportional phase correction metric from the quantizer error signal and providing phase values for plural subbands, derived from the proportional phase correction metric, to the filter for use in removing the self-interference in the input data.
Dependencies are inferred from the claim text.