Low-noise oscillator amplitude regulator
A frequency generation solution controls an oscillator amplitude using two feedback paths to generate high frequency signals with lower power consumption and lower noise. A first feedback path provides continuous control of the oscillator amplitude responsive to an amplitude detected at the oscillator output. A second feedback path provides discrete control of the amplitude regulating parameter(s) of the oscillator responsive to the detected oscillator amplitude. Because the second feedback path enables the adjustment of the amplitude regulating parameter(s), the second feedback path enables an amplifier in the first feedback path to operate at a reduced gain, and thus also at a reduced power and a reduced noise, without jeopardizing the performance of the oscillator.
1. A frequency generation circuit comprising:
an oscillator comprising an oscillator output, a first control input, and a second control input;
a detector configured to detect an amplitude of the oscillator output;
a first feedback path operatively connecting the detector to the first control input, the first feedback path configured to control the amplitude of the oscillator output responsive to the detected amplitude by continuously applying a first control signal to the first control input; and
a second feedback path operatively connecting the detector to the second control input, the second feedback path comprising a control circuit configured to control a second control signal to:
prevent one or more amplitude regulating parameters of the oscillator from changing when the oscillator powers on; and
allow the one or more amplitude regulating parameters of the oscillator to change responsive to the detected amplitude after the oscillator powers on and stabilizes.
2. The frequency generation circuit of claim 1 wherein the control circuit is further configured to control the second control signal to change the one or more amplitude regulating parameters responsive to an upcoming random access channel transmission event, an upcoming radio transmission event, and/or an upcoming radio reception event.
3. The frequency generation circuit of claim 1 wherein the first feedback path is configured to control the amplitude of the oscillator output, responsive to the detected amplitude, by continuously controlling a gain of the oscillator.
4. The frequency generation circuit of claim 1 , wherein the one or more amplitude regulating parameters comprise at least one of:
an oscillator bias current;
a number of oscillator gm cells;
a bias point of one or more of the oscillator gm cells; and
a variable resistance connected in parallel with a core of the oscillator.
5. A method of controlling an oscillator comprising an oscillator output, a first control input, and a second control input, the method comprising:
detecting an amplitude of the oscillator output;
controlling the amplitude of the oscillator output, responsive to the detected amplitude, by continuously applying a first control signal to the first control input; and
controlling one or more amplitude regulating parameters of the oscillator by controlling a second control signal applied to the second control input to:
prevent the one or more amplitude regulating parameters of the oscillator from changing when the oscillator powers on; and
allow the one or more amplitude regulating parameters of the oscillator to change responsive to the detected amplitude after the oscillator powers on and stabilizes.
6. The method of claim 5 wherein controlling the second control signal comprises controlling the second control signal to change the one or more amplitude regulating parameters responsive to an upcoming random access channel transmission event, an upcoming radio transmission event, and/or an upcoming radio reception event.
7. The method of claim 5 wherein controlling the amplitude of the oscillator output comprises continuously controlling a gain of the oscillator responsive to the detected amplitude.
8. The method of claim 5 wherein the one or more amplitude regulating parameters comprise at least one of:
an oscillator bias current;
a number of oscillator gm cells;
a bias point of one or more of the oscillator gm cells; and
a variable resistance connected in parallel with a core of the oscillator.
9. A wireless communication device comprising a frequency generation circuit, said frequency generation circuit comprising:
an oscillator comprising an oscillator output, a first control input, and a second control input;
a detector configured to detect an amplitude of the oscillator output;
a first feedback path operatively connecting the detector to the first control input, the first feedback path configured to control the amplitude of the oscillator output responsive to the detected amplitude by applying a first control signal to the first control input; and
a second feedback path operatively connecting the detector to the second control input, the second feedback path comprising a control circuit configured to control a second control signal to:
prevent one or more amplitude regulating parameters of the oscillator from changing when the oscillator powers on; and
allow the one or more amplitude regulating parameters of the oscillator to change responsive to the detected amplitude after the oscillator powers on and stabilizes.
10. The wireless communication device of claim 9 wherein the control circuit is further configured to control the second control signal to change the one or more amplitude regulating parameters responsive to an upcoming random access channel transmission event, an upcoming radio transmission event, and/or an upcoming radio reception event.
11. The wireless communication device of claim 9 wherein the first feedback path is configured to control the amplitude of the oscillator output, responsive to the detected amplitude, by continuously controlling a gain of the oscillator.
12. The wireless communication device of claim 9 , wherein the one or more amplitude regulating parameters comprise at least one of:
an oscillator bias current;
a number of oscillator gm cells;
a bias point of one or more of the oscillator gm cells; and
a variable resistance connected in parallel with a core of the oscillator.