Circuits and systems for wideband quadrature signal generation

Abstract

Wide band quadrature signal generation includes a frequency synthesizer generating a LO or 2×LO signal, a polyphase filter coupled to receive the LO signal and generate first in-phase and quadrature LO signals, a 2:1 frequency divider coupled to receive the 2×LO signal and generate second in-phase and quadrature LO signals, and a LO signal selector for selecting either the first or second in-phase LO signals as an output in-phase LO signal and either the first or second quadrature LO signals as an output quadrature LO signal based on an output frequency. In some embodiments, when the output frequency is above a threshold, the first in-phase and quadrature LO signals are selected as the output in-phase and quadrature LO signals and when the output frequency is at or below the threshold, the second in-phase and quadrature LO signals are selected as the output in-phase and quadrature LO signals.

What is claimed is: 
     
         1 - 20 . (canceled) 
     
     
         21 . A circuit for generating quadrature local oscillator (LO) signals, the circuit comprising:
 a polyphase filter for generating a first in-phase LO signal and a first quadrature LO signal from a LO signal;   a frequency divider for generating a second in-phase LO signal and a second quadrature LO signal from the LO signal; and   a LO signal selector for selecting either the first or second in-phase LO signals as an output in-phase LO signal and selecting either the first or second quadrature LO signals as an output quadrature LO signal based on a desired output frequency for the output in-phase LO signal or the output quadrature LO signal.   
     
     
         22 . The circuit of claim  1 , further comprising:
 a frequency synthesizer for generating the LO signal; and   a low-pass filter coupled between the frequency synthesizer and the polyphase filter.   
     
     
         23 . The circuit of claim  1 , wherein the LO signal selector:
 selects the first in-phase LO signal as the output in-phase LO signal when the desired output frequency is above a threshold frequency;   selects the first quadrature LO signal as the output quadrature LO signal when the desired output frequency is above the threshold frequency;   selects the second in-phase LO signal as the output in-phase LO signal when the desired output frequency is at or below the threshold frequency; and   selects the second quadrature LO signal as the output quadrature LO signal when the desired output frequency is at or below the threshold frequency.   
     
     
         24 . The circuit of claim  1 , wherein the desired output frequency is determined based on a frequency select input provided to the LO signal selector,
 wherein the frequency select input is provided to the frequency synthesizer to set a frequency of the first LO signal.   
     
     
         25 . The circuit of claim  1 , wherein the LO signal selector comprises a frequency detector for determining the desired output frequency based on a frequency of the first in-phase LO signal, a frequency of the second in-phase LO signal, a frequency of the first quadrature LO signal, or a frequency of second quadrature LO signal. 
     
     
         26 . The circuit of claim  1 , wherein the output in-phase LO signal and the output quadrature LO signal have a same amplitude and a 90 degree phase shift when the desired output frequency is within a range of operating frequencies for the circuit. 
     
     
         27 . A quadrature modulator, the modulator comprising:
 a quadrature local oscillator (LO) generator for generating an in-phase LO signal and a quadrature LO signal, the in-phase LO signal and the quadrature LO signal having a desired frequency;   a first mixer for modulating the in-phase LO signal utilizing a first data signal;   a second mixer for modulating the quadrature LO signal utilizing a second data signal; and   a summer for combining the modulated in-phase LO signal and the modulated quadrature LO signal to form a composite signal.   
     
     
         28 . The quadrature modulator of claim  7 , wherein the quadrature LO generator generates the in-phase LO signal and the quadrature LO signal utilizing a polyphase filter when the desired frequency is above a frequency threshold and generates the in-phase LO signal and the quadrature LO signal utilizing a frequency divider when the desired frequency is at or below the frequency threshold. 
     
     
         29 . The quadrature modulator of claim  8 , wherein the in-phase LO signal and the quadrature LO signal have a same amplitude and a 90 degree phase shift when the desired frequency is within a range of operating frequencies for the modulator. 
     
     
         30 . The quadrature modulator of claim  7 , wherein:
 the frequency threshold is 1.15 GHz; and   the range of operating frequencies extends from 0.5 GHz to 3 GHz.   
     
     
         31 . The quadrature modulator of claim  8 , wherein:
 the polyphase filter generates a first candidate in-phase LO signal and a first candidate quadrature LO signal; and   the frequency divider generates a second candidate in-phase LO signal and a second candidate quadrature LO signal.   
     
     
         32 . The quadrature modulator of claim  11 , wherein:
 the quadrature LO generator further comprises a LO signal selector that:
 selects the first candidate in-phase LO signal as the in-phase LO signal when the desired frequency is above the frequency threshold; 
 selects the first candidate quadrature LO signal as the quadrature LO signal when the desired frequency is above the frequency threshold; 
 selects the second candidate in-phase LO signal as the in-phase LO signal when the desired frequency is at or below the frequency threshold; and 
 selects the second candidate quadrature LO signal as the quadrature LO signal when the desired frequency is at or below the frequency threshold. 
   
     
     
         33 . The quadrature modulator of claim  8 , wherein the desired frequency is determined based on a frequency select input provided to the LO signal selector. 
     
     
         34 . The quadrature modulator of claim  8 , wherein the quadrature modulator operates in a low-power mode where the polyphase filter or the frequency divider is disabled based on the desired frequency. 
     
     
         35 . A receiver comprising:
 a phase detector configured to a composite signal containing a first modulated in-phase local oscillator (LO) signal and a first modulated quadrature LO signal;   a quadrature LO generator configured to generate a second in-phase LO signal and a second quadrature LO signal;   a first mixer configured to mix the second in-phase LO signal with the composite signal and generate a recovered version of a first in-phase LO signal; and   a second mixer configured to mix the second quadrature LO signal with the composite signal and generate a recovered version of the first quadrature LO signal.   
     
     
         36 . The receiver of claim  15 , wherein the phase detector is further configured to generate a phase reference for synchronizing phases of the first modulated in-phase local oscillator (LO) signal and the first modulated quadrature LO signal with phases of the second in-phase LO signal and the second quadrature LO signal from the composite signal. 
     
     
         37 . The receiver of claim  15 , wherein the phase detector is further configured to include a frequency offset to account for Doppler frequency shifts caused by relative motion between the receiver and a transmitter. 
     
     
         38 . The receiver of claim  15 , wherein quadrature LO generator is further configured to generate the second in-phase LO signal and the second quadrature LO signal at a desired frequency with a synchronizing phase shift provided by the phase detector. 
     
     
         39 . The receiver of claim  15 , wherein the first mixer is further configured to multiply the composite signal and the second in-phase LO signal to result in the recovered version of the first in-phase LO signal and a signal at twice a desired frequency. 
     
     
         40 . The receiver of claim  19 , further comprising:
 a low pass filter configured to remove the signal at twice the desired frequency from an output of the first mixer.