Quadrature VCO system and method
A low-power quadrature generator is provided for accurately generating in-phase signals and quadrature signals.
1. A quadrature signal generator system for generating in-phase and quadrature signals, comprising:
an in-phase signal generator having a first voltage controlled oscillator (VCO) configured to generate in-phase signals;
a quadrature signal generator having a second voltage controlled oscillator (VCO) configured to generate quadrature signals;
a first VCO control signal generator for producing a first VCO control signal; and
a second VCO control signal generator for producing a second VCO control signal;
wherein the first VCO control signal is used to control the first and second voltage controlled oscillators whilst the first voltage controlled oscillator is being locked to a reference signal, and thereafter the second VCO control signal is used to control the second VCO to produce the quadrature signals.
2. The system according to claim 1 , wherein the second VCO control signal generator is configured to receive the in-phase signals generated by the in-phase signal generator.
3. The system according to claim 1 , wherein the first VCO control signal generator is configured to detect when said first VCO is locked to said reference signal, and to output a lock signal in dependence thereon, the system further comprising a switching arrangement configured to receive said lock signal, and to switch the control signal provided to said second VCO to said second VCO control signal in dependence on said lock signal.
4. The system according to claim 3 , wherein said lock signal takes a first value whilst said first VCO is being locked to a reference signal and takes a second value thereafter.
5. The system according to claim 1 further comprising a buffer, the first VCO control signal being provided to said second VCO via said buffer.
6. A method of generating in-phase and quadrature signals, comprising:
a) generating, using a first voltage controlled oscillator, an in-phase signal in response to a first control signal;
b) locking said in-phase signal to a reference signal;
c) generating, using a second voltage controlled oscillator, a quadrature signal in response to the first control signal, whilst said in-phase signal is being locked to said reference signal; and
d) once said in-phase signal has been locked to said reference signal, applying a second control signal to said second voltage controlled oscillator in place of said first control signal, so as to generate said quadrature signal in phase quadrature to said in-phase signal.
7. The method according to claim 6 further comprising the step of buffering said first control signal, said generating of said quadrature signal being performed in response to said buffered first control signal.