Coherent adaptive calibration system and method

Abstract

A receiver is adaptively calibrated by using a coherent reference signal. The reference signal is selected to be offset from a center frequency of the calibration signal such that the resultant product is offset from baseband by some small amount. The resultant product is used to determine a next value of the calibration parameters.

1 . A coherent adaptive calibration method for calibration of a receiver, comprising the steps of: 
 summing a series of first channel signal samples with a first channel offset correction parameter to produce a corrected series of first channel samples;    summing a series of second channel signal samples with a second channel offset correction parameter, multiplying by a gain imbalance correction parameter and summing a product of said corrected series of said first channel samples and a phase error correction parameter to create a corrected set of second channel samples, wherein said second channel is orthogonal to said first channel;    multiplying said corrected series of first channel samples with a first sinusoidal waveform to determine a first product;    multiplying said corrected series of second channel samples with a second sinusoidal waveform to determine a second product, said second sinusoidal waveform being 90 degrees out of phase with said first sinusoidal waveform;    filtering said first product to determine a first channel gain imbalance measurement;    filtering said second product to determine a second channel gain imbalance measurement; and    determining a next value of said gain imbalance correction parameter based upon said first and second channel gain imbalance measurements.    
   
   
       2 . The method of  claim 1  wherein said step of determining is executed by directly taking a difference between said first and second channel gain imbalance measurements.  
   
   
       3 . The method of  claim 1  wherein said series of channel samples comprises a calibration signal received over the air.  
   
   
       4 . The method of  claim 1  wherein said series of channel samples comprises energy received over the air and a calibration signal from an internal source.  
   
   
       5 . The method of  claim 1  wherein said step of determining said next value of said gain imbalance correction parameter is executed using a stochastic gradient equation.  
   
   
       6 . The method of  claim 1  wherein said steps of filtering and multiplying are executed digitally.  
   
   
       7 . The method of  claim 6  further comprising the steps of: 
 digitally multiplying said corrected series of second channel samples with said first sinusoidal waveform to determine a third product;    digitally filtering said third product to determine a phase error measurement; and    determining a next value of said phase correction parameter based upon said first gain imbalance measurement and said phase error measurement.    
   
   
       8 . A receiver, comprising: 
 a first summation module configured to sum a series of first channel signal samples with a first channel offset correction parameter to produce a corrected series of first channel samples;    a second summation module configured to sum a series of second channel signal samples with a second channel offset correction parameter, multiplying by a gain imbalance correction parameter and summing a product of said corrected series of said first channel samples and a phase error correction parameter to create a corrected set of second channel samples, wherein said second channel is orthogonal to said first channel;    means for multiplying said corrected series of first channel samples with a first sinusoidal waveform to determine a first product;    means for multiplying said corrected series of second channel samples with said first sinusoidal waveform to determine a third product;    means for filtering said first product to determine a first channel gain imbalance measurement;    means for filtering said third product to determine a phase error measurement; and    means for determining a next value of said phase correction parameter based upon said first gain imbalance measurement and said phase error measurement.    
   
   
       9 . A receiver, comprising: 
 a first summation module configured to sum a series of first channel signal samples with a first channel offset correction parameter to produce a corrected series of first channel samples;    a second summation module configured to sum a series of second channel signal samples with a second channel offset correction parameter, multiplying by a gain imbalance correction parameter and summing a product of said corrected series of said first channel samples and a phase error correction parameter to create a corrected set of second channel samples, wherein said second channel is orthogonal to said first channel;    means for multiplying said corrected series of first channel samples with a first sinusoidal waveform to determine a first product;    means for multiplying said corrected series of second channel samples with a second sinusoidal waveform to determine a second product, said second sinusoidal waveform being 90 degrees out of phase with said first sinusoidal waveform;    means for filtering said first product to determine a first channel gain imbalance measurement;    means for filtering said second product to determine a second channel gain imbalance measurement; and    means for determining a next value of said gain imbalance correction parameter based upon said first and second channel gain imbalance measurements.    
   
   
       10 . The receiver of  claim 9  wherein said means for multiplying and said means for filtering are digital.  
   
   
       11 . A receiver, comprising: 
 a first summer configured to sum a series of first channel signal samples with a first channel offset correction parameter to produce a corrected series of first channel samples;    a first multiplier configured to multiply said corrected series of said first channel samples and a phase error correction parameter;    a second summer configured to sum a series of second channel signal samples with a second channel offset correction parameter;    a second multiplier configured to multiply an output of said second summer by a gain imbalance correction;    a third summer configured to sum an output of said first multiplier and said second multiplier to create a corrected set of second channel samples, wherein said second channel is orthogonal to said first channel;    a third multiplier configured to multiply said corrected series of first channel samples by a first digitized sinusoidal waveform;    a fourth multiplier configured to multiply said corrected series of second channel samples by a second digitized sinusoidal waveform, said second digitized sinusoidal waveform being 90 degrees out of phase with said first digitized sinusoidal waveform;    a first digital filter configured to filter an output of said third multiplier to determine a first channel gain imbalance measurement;    a second digital filter configured to filter an output of said fourth multiplier to determine a second channel gain imbalance measurement; and    a calculator configured to determine a next value of said gain imbalance correction parameter based upon said first and second channel gain imbalance measurements.    
   
   
       12 . A receiver, comprising: 
 a first summer configured to sum a series of first channel signal samples with a first channel offset correction parameter to produce a corrected series of first channel samples;    a first multiplier configured to multiply said corrected series of said first channel samples and a phase error correction parameter;    a second summer configured to sum a series of second channel signal samples with a second channel offset correction parameter;    a second multiplier configured to multiply an output of said second summer by a gain imbalance correction;    a third summer configured to sum an output of said first multiplier and said second multiplier to create a corrected set of second channel samples, wherein said second channel is orthogonal to said first channel;    a third multiplier configured to multiply said corrected series of first channel samples by a first digitized sinusoidal waveform;    a fourth multiplier configured to multiply said corrected series of second channel samples by said first sinusoidal waveform to determine a third product;    a first digital filter configured to filter an output of said third multiplier to determine a first channel gain imbalance measurement;    a second digital filter configured to filter an output of said fourth multiplier to determine a phase error measurement; and    a calculator configured to determine a next value of said phase correction parameter based upon said first gain imbalance measurement and said phase error measurement.