Harmonic Reject Receiver Architecture and Mixer

Abstract

Receiver architectures and methods of processing harmonic rich input signals employing harmonic suppression mixers are disclosed herein. The disclosed receivers, mixers, and methods enable a receiver to achieve the advantages of switching mixers while greatly reducing the mixer response to the undesired harmonics. A harmonic mixer can include a plurality of mixers coupled to an input signal. A plurality of phases of a local oscillator signal can be generated from a single local oscillator output. Each of the phases can be used to drive an input of one of the mixers. The mixer outputs can be combined to generate a frequency converted output that has harmonic rejection.

What is claimed is: 
     
         1 . A harmonic reject mixer comprising:
 a plurality of mixers, each mixer having an input coupled to a common RF input;   a phase shifter having an input coupled to a common LO input and a plurality of phase shifted outputs, each of the outputs coupled to a LO input on a corresponding mixer; and   a combiner having a plurality of inputs, each input coupled to an output from an associated mixer, and configured to provide a combined output.   
     
     
         2 . The mixer of  claim 1 , wherein each of the plurality of mixers comprises a switching mixer. 
     
     
         3 . The mixer of  claim 1 , wherein each of the plurality of mixers comprises a CMOS switching mixer. 
     
     
         4 . The mixer of  claim 1 , wherein the phase shifter comprises a plurality of distinct phase shifters, each configured to provide a distinct predetermined phase shift. 
     
     
         5 . The mixer of  claim 1 , wherein the phase shifter is configured to generate a plurality of phase shifted outputs equally spaced about the span of −90 to +90 degrees. 
     
     
         6 . The mixer of  claim 1 , wherein:
 the plurality of mixers comprise three distinct mixers; and   the plurality of phase shifted outputs comprise outputs shifted by −45, 0, and +45 degrees.   
     
     
         7 . The mixer of  claim 1 , further comprising a plurality of amplifiers, each of the plurality of amplifiers coupled to a distinct one of the plurality of mixers and configured to amplify a mixer output by a gain based at least in part on an LO phase shift. 
     
     
         8 . A method of harmonic rejection mixing, the method comprising:
 generating a plurality of phases of a LO signal;   mixing an input signal with each of the plurality of phases of the LO signal to generate a plurality of mixed output signals; and   combining the plurality of mixed output signals to provide a mixer output.   
     
     
         9 . The method of  claim 8 , wherein mixing the input signal comprises:
 coupling the input signal to a plurality of switching mixers; and   driving each of the plurality of switching mixers with a distinct one of the plurality of phase of the LO signal.   
     
     
         10 . The method of  claim 8 , wherein generating the plurality of phases of the LO signal comprises phase shifting the LO signal using a plurality of distinct phase shifters, each of the plurality of distinct phase shifters providing a distinct phase shift. 
     
     
         11 . The method of  claim 8 , wherein generating the plurality of phases of the LO signal comprises generating an odd number of distinct phases of the LO signal equally spaced about a span of −90 to +90 degrees. 
     
     
         12 . The method of  claim 8 , wherein combining the plurality of mixed output signals comprises summing the plurality of mixed output signals. 
     
     
         13 . The method of  claim 8 , further comprising amplifying each of the plurality of mixed output signals by a gain based on an LO phase shift. 
     
     
         14 . The method of  claim 8 , wherein the input signal comprises an RF signal in a multi-octave operating band. 
     
     
         15 . The method of  claim 8 , wherein the input signal comprises a television signal. 
     
     
         16 . A quadrature mixer comprising:
 a plurality of harmonic reject mixers, each mixer having an input coupled to one of a plurality of phases of an input signal, and each mixer having an input coupled to a phase shifted LO;   a first combiner having inputs coupled to outputs from a first subset of the plurality of harmonic reject mixers, and an output configured to provide a quadrature output; and   a second combiner having inputs coupled to outputs from a second subset of the plurality of harmonic reject mixers, and an output configured to provide an in-phase output.   
     
     
         17 . The quadrature mixer of  claim 16 , wherein each of the plurality of harmonic reject mixers comprises:
 a plurality of switching mixers, each switching mixer having an input coupled to a common RF input;   a phase shifter having an input coupled to a common LO input and a plurality of phase shifted outputs, each of the outputs coupled to a LO input on a corresponding mixer; and   a combiner having a plurality of inputs, each input coupled to an output from one of the plurality of switching mixers, and configured to provide a combined output.   
     
     
         18 . The quadrature mixer of  claim 16 , further comprising a polyphase filter having an input arid a plurality of outputs, each of the plurality of outputs configured to provide the plurality of phases of the input signal. 
     
     
         19 . A method of quadrature mixing, the method comprising:
 phase shifting an input signal to generate a plurality of phases of the input signal;   generating a plurality of phases of an LO signal;   mixing each of the plurality of phases of the input signal with a phase of the LO from the plurality of phases of the LO signal to generate a plurality of mixer outputs;   combining a first subset of mixer outputs to generate a quadrature mixer output; and   combining a second subset of mixer outputs to generate an in-phase mixer output.   
     
     
         20 . A receiver comprising:
 a filter having an input coupled to an RF input, and a filtered output; and   a harmonic reject down converter having an input coupled to the filtered output, a Local Oscillator (LO) input configured to receive an LO signal, a quadrature output, and an in-phase output.   
     
     
         21 . The receiver of  claim 20 , wherein the filter comprises a programmable bandwidth filter. 
     
     
         22 . The receiver of  claim 20 , wherein the harmonic reject down converter comprises:
 a plurality of switching mixers, each switching mixer having an input coupled to a common RF input;   a phase shifter having an input coupled to a common LO input and a plurality of phase shifted outputs, each of the outputs coupled to a LO input on a corresponding mixer; and   a combiner having a plurality of inputs, each input coupled to an output from one of the plurality of switching mixers, and configured to provide a combined output.   
     
     
         23 . The receiver of  claim 20 , wherein the RF input signal comprises a television signal.