Receiver architecture with digitally generated intermediate frequency

Abstract

A receiver can be configured to include an RF front end that is configured to downconvert a received signal to a baseband signal or a low Intermediate Frequency (IF) signal. The receiver can downconvert the desired signal from an RF frequency in the presence of numerous interference sources to a baseband or low IF signal for filtering and channel selection. The filtered baseband or low IF signal can be converted to a digital representation. The digital representation of the signal can be upconverted in the digital domain to a programmable IF frequency. The digital IF signal can be converted to an analog IF signal that can be processed by legacy hardware.

1 . A receiver comprising: 
 a downconverter configured to downconvert an input signal to a signal in a first frequency band;    an analog to digital converter (ADC) coupled to the downconverter and configured to digitize the signal in the first frequency band to produce a digital representation of the signal in the first frequency band; and    a digital upconverter configured to upconvert the digital representation of the signal in the first frequency band to a digital representation of the signal in a second frequency band.    
   
   
       2 . The receiver of  claim 1 , wherein the first frequency band comprises one of a baseband frequency band or a low Intermediate Frequency (IF) band based on a mode of the receiver.  
   
   
       3 . The receiver of  claim 1 , wherein the downconverter comprises: 
 an in-phase downconverter configured to downconvert an in-phase component of the input signal to the first frequency band; and    a quadrature downconverter configured to downconvert a quadrature component of the input signal to the first frequency band.    
   
   
       4 . The receiver of  claim 1 , wherein the downconverter comprises: 
 an in-phase downconverter configured to downconvert an in-phase component of the input signal to substantially a baseband in-phase signal; and    a quadrature downconverter configured to downconvert a quadrature component of the input signal to substantially a baseband quadrature signal.    
   
   
       5 . The receiver of  claim 1 , wherein the downconverter comprises: 
 an in-phase downconverter configured to downconvert an in-phase component of the input signal to a in-phase low Intermediate Frequency (IF) signal; and    a quadrature downconverter configured to downconvert a quadrature component of the input signal to a quadrature low IF signal.    
   
   
       6 . The receiver of  claim 1 , further comprising a filter configured to perform at least partial channel selection of the signal in the first frequency band prior to the ADC.  
   
   
       7 . The receiver of  claim 1 , further comprising a digital filter configured to perform channel selection of the digital representation of the signal in the first frequency band.  
   
   
       8 . The receiver of  claim 1 , wherein the digital upconverter comprises: 
 a first digital upconverter configured to digitally upconvert an in-phase component of the input signal to an in-phase digital signal at a desired Intermediate Frequency (IF); and    a second digital upconverter configured to digitally upconvert a quadrature component of the input signal to a quadrature digital signal at the desired IF.    
   
   
       9 . The receiver of  claim 8 , further comprising a digital signal combiner configured to combine the in-phase digital signal at the desired IF with the quadrature digital signal at the desired IF.  
   
   
       10 . A receiver comprising: 
 a first frequency converter configured to downconvert a received signal to an in-phase baseband signal component;    a second frequency converter configured to downconvert the received signal to a quadrature baseband signal component;    a first analog filter coupled to the first frequency converter and configured to perform at least partial channel selection on the in-phase baseband signal component;    a second analog filter coupled to the second frequency converter and configured to perform at least partial channel selection on the quadrature baseband signal component;    a first Analog to Digital Converter (ADC) coupled to the first analog filter and configured to convert the in-phase baseband signal component to a digital in-phase baseband signal component;    a second ADC coupled to the second analog filter and configured to convert the quadrature baseband signal component to a digital quadrature baseband signal component;    a first digital filter coupled to the first ADC and configured to digitally filter the digital in-phase baseband signal component to generate a digitally filtered in-phase baseband signal component;    a second digital filter coupled to the second ADC and configured to digitally filter the digital quadrature baseband signal component to generate a digitally filtered quadrature baseband signal component;    a first digital upconverter configured to digitally upconvert the digitally filtered in-phase baseband signal component to an in-phase Intermediate Frequency (IF) signal component at a desired IF;    a second digital upconverter configured to digitally upconvert the digitally filtered quadrature baseband signal component to a quadrature IF signal component at the desired IF; and    a digital signal combiner configured to combine the in-phase IF signal component with the quadrature IF signal component.    
   
   
       11 . A method of receiving a signal, the method comprising: 
 frequency converting an input signal to an intermediate signal in a first frequency band;    digitizing the intermediate signal; and    digitally converting the intermediate signal to a second frequency band.    
   
   
       12 . The method of  claim 11 , wherein frequency converting the input signal comprises: 
 downconverting the input signal to an in-phase baseband signal component; and    downconverting the input signal to a quadrature baseband signal component.    
   
   
       13 . The method of  claim 11 , wherein the intermediate signal comprises: 
 an in-phase baseband signal component; and    a quadrature baseband signal component.    
   
   
       14 . The method of  claim 11 , further comprising performing partial channel selection on the intermediate signal.  
   
   
       15 . The method of  claim 11 , wherein digitizing the intermediate signal comprises: 
 digitizing an in-phase signal component of the intermediate signal; and    digitizing a quadrature signal component of the intermediate signal.    
   
   
       16 . The method of  claim 11 , wherein digitally converting the intermediate signal comprises: 
 digitally upconverting an in-phase signal component of the intermediate signal to an in-phase Intermediate Frequency (IF) component at a desired IF;    digitally upconverting a quadrature signal component of the intermediate signal to a quadrature IF component at the desired IF; and    combining the in-phase IF component with the quadrature IF component.    
   
   
       17 . A method of calibrating a quadrature receiver, the method comprising: 
 injecting a calibration tone to a signal path of a quadrature receiver;    detecting an amplitude and phase imbalance of the quadrature receiver;    adjusting a gain of at least one of an in-phase and a quadrature signal path based on the amplitude imbalance; and    adjusting a phase of at least one of the in-phase and quadrature signal paths based on the phase imbalance.    
   
   
       18 . The method of  claim 17 , wherein injecting the calibration tone comprises injecting one of a quadrature or an in-phase Local Oscillator (LO) signal to the signal path.  
   
   
       19 . The method of  claim 18 , wherein the one of the quadrature or in-phase LO signal is synchronized with a LO signal used to downconvert the calibration tone to a DC signal.  
   
   
       20 . The method of  claim 17 , wherein detecting the amplitude and phase imbalance of the quadrature receiver comprises: 
 downconverting an in-phase Intermediate Frequency (IF) signal component to a first DC signal;    downconverting a quadrature IF signal component to a second DC signal;    combining the first and second DC signals to generate a combined DC signal; and    determining the phase imbalance based on the combined DC signal.    
   
   
       21 . A quadrature receiver calibration apparatus, the apparatus comprising: 
 a tone generator configured to generate a calibration tone;    a coupler configured to couple the calibration tone to a signal path of the quadrature receiver;    a detector configured to detect an in-phase and quadrature signal component when the calibration tone is coupled to the signal path;    a gain feedback module configured to adjust a gain of at least one of an in-phase signal path and a quadrature signal path; and    a phase feedback module configured to adjust a phase of at least one of the in-phase signal path and the quadrature signal path.