Dynamic frequency correction in delta-sigma based software defined receiver

Abstract

A method and apparatus for dynamically modifying filter characteristics of a Delta-Sigma modulator to accommodate for Doppler shift. A transceiver in a wireless cellular communication system for adapt to changes in the RF carrier frequency for maintaining signal integrity by applying a pilot tone in calibration to determine a frequency shift response for a bandpass filter. During operation, the system is operative to determine a Doppler shift and to shift the bandpass filter in response.

What is claimed is: 
     
         1 . An apparatus comprising:
 an antenna operable to receive an RF signal;   a memory for storing a configuration parameter;   a software definable radio for configuring an initial filter response, filtering the RF signal to generate a filtered RF signal, and for reconfiguring the filter response in response to the configuration parameter; and   a processor operable to process the filtered RF signal, determine a quality factor of the filtered RF signal, retrieve the configuration parameter in response to the quality factor, and to couple the configuration parameter to a software definable.   
     
     
         2 . The apparatus of  claim 1  wherein the reconfiguration the filter involves changing the center frequency of a bandpass filter. 
     
     
         3 . The apparatus of  claim 1  wherein the determining the quality factor involves determining a center frequency of the filtered RF signal and comparing that to the center frequency of the initial filter response. 
     
     
         4 . The apparatus of  claim 1  wherein the software definable radio includes a sigma delta modulator operable to demodulate the RF signal. 
     
     
         5 . The apparatus of  claim 1  wherein the configuring the initial filter response involves configuring a filter bandwidth and a filter center frequency. 
     
     
         6 . The apparatus of  claim 5  wherein reconfiguring the filter response includes changing the filter bandwidth. 
     
     
         7 - 16 . (canceled)