Method and apparatus for controlling a voltage controlled oscillator

An apparatus for controlling a voltage controlled oscillator (VCO), the apparatus comprising:

• a rectifier for rectifying an output signal of the VCO to produce an envelope signal proportional to an amplitude of the output signal;
• an integrator coupled to the rectifier for integrating the envelope signal to produce a comparison signal, the integrator further coupled to a control signal and arranged such that, in response to a change in the envelope signal, when the control signal indicates that the VCO is to operate in a first mode of operation, the comparison signal is allowed to change at a first rate, and, when the control signal indicates that the VCO is to operate in a second mode, the comparison signal is allowed to change at a second rate different from the first rate;
• and
• a comparator, coupled to the integrator and coupled to a reference signal, for comparing the comparison signal with the reference signal to produce a bias signal, wherein the bias signal is for controlling a gain of the VCO.

An amplitude-regulated voltage controlled oscillator (ARVCO) comprising:

• a voltage controlled oscillator (VCO), including a tank circuit for setting an operating frequency of the VCO, and a variable-gain cell coupled to the tank circuit for providing a gain for sustaining an oscillation;
• a rectifier coupled to the VCO for rectifying an output signal of the VCO to produce an envelope signal proportional to an amplitude of the output signal;
• an integrator coupled to the rectifier for integrating the envelope signal to produce a comparison signal, and responsive to a control signal, the integrator arranged such that, in response to a change in the envelope signal, when the control signal indicates that the VCO is to operate in a first mode of operation, the comparison signal is allowed to change at a first rate, and, when the control signal indicates that the VCO is to operate in a second mode of operation, the comparison signal is allowed to change at a second rate different from the first rate;
• and
• a comparator, coupled to the integrator and coupled to a reference signal, for comparing the comparison signal with the reference signal to produce a bias signal, wherein the bias signal is coupled to the variable-gain cell of the VCO for controlling the gain of the VCO.

A complementary metal oxide semiconductor (CMOS) integrated circuit comprising:

• a voltage controlled oscillator (VCO), including a tank circuit for setting an operating frequency of the VCO, and a variable-gain cell coupled to the tank circuit for providing a gain for sustaining an oscillation;
• a rectifier coupled to the VCO for rectifying an output signal of the VCO to produce an envelope signal proportional to an amplitude of the output signal;
• an integrator coupled to the rectifier for integrating the envelope signal to produce a comparison signal, and responsive to a control signal, the integrator arranged such that, in response to a change in the envelope signal, when the control signal indicates that the VCO is to operate in a first mode, the comparison signal is allowed to change at a first rate, and, when the control signal indicates that the VCO is to operate in a second mode, the comparison signal is allowed to change at a second rate different from the first rate;
• and
• a comparator, coupled to the integrator and coupled to a reference signal, for comparing the comparison signal with the reference signal to produce a bias signal, wherein the bias signal is coupled to the variable-gain cell of the VCO for controlling the gain of the VCO.