Controlling the frequency of an oscillator
A technique includes selectively coupling impedances to an oscillator to establish a first frequency of operation of the oscillator. The technique includes repeating the selective coupling in a feedback loop to cause the first frequency to be near a second frequency.
1. A method comprising:
selectively coupling impedances to an oscillator to establish a first frequency of operation of the oscillator;
repeating the coupling in a feedback loop to cause the first frequency to be near a second frequency of a wireless signal; and
delaying the selective coupling to impose a rate limit at which the first frequency changes.
2. The method of claim 1 , wherein the second frequency comprises a frequency of a wireless signal.
3. The method of claim 1 , further comprising:
using the oscillator to establish a reference frequency for a transceiver.
4. The method of claim 1 , wherein the act of selectively coupling comprises:
selectively coupling capacitive elements to the oscillator.
5. The method of claim 1 , wherein the act of selectively coupling comprises:
selectively coupling the impedances to an oscillator tank of the oscillator.
6. The method of claim 1 , wherein the selective coupling occurs in response to digital data indicative of the first frequency.
7. The method of claim 6 , further comprising:
delaying the selective coupling to impose a rate limit at which the first frequency changes.
8. The method of claim 1 , further comprising:
associating switches with bits of the digital data, wherein the act of selectively coupling comprises selectively activating the switches to couple the impedances to the oscillator.
9. The method of claim 1 , wherein the repeating the changing adjusts the first frequency within a first resolution, the method further comprising:
adjusting the first frequency outside of the feedback within a second resolution larger than the first resolution.
10. The method of claim 1 , further comprising:
using the oscillator to generate a signal;
synchronizing the selective coupling in response to a timing of a signal generated by the oscillator.
11. The method of claim 1 , further comprising:
precharging at least some of the impedances when not coupled to the oscillator.
12. The method of claim 11 , further comprising:
using the oscillator to generate a signal, wherein
the precharging comprises coupling at least some of the impedances to the signal.
13. An apparatus comprising:
impedances;
an oscillator core; and
a circuit to selectively couple the impedances to the oscillator core to establish a first frequency of operation of the oscillator core and repeat the coupling in a feedback loop to cause the first frequency to be near a second frequency of a wireless signal, and regulate the selective coupling of the impedances to the oscillator core to control a rate at which a total impedance coupled to the oscillator core changes to impose a limit on a rate at which the first frequency changes.
14. The apparatus of claim 13 , wherein the second frequency comprises a frequency of a wireless signal.
15. The apparatus of claim 13 , further comprising:
a radio frequency receiver to synchronize an operation to the first frequency.
16. The apparatus of claim 13 , further comprising:
a radio frequency transmitter to synchronize an operation to the first frequency.
17. The apparatus of claim 13 , wherein the circuit selectively couples capacitive elements to the oscillator core to establish the first frequency.
18. The apparatus of claim 13 , wherein the circuit selective couples the impedances in response to digital data indicative of the first frequency.
19. The apparatus of claim 13 , further comprising switches, wherein the circuit, in response to the digital data, drives the switches with signals to cause the switches to selectively couple the impedance elements to the oscillator and delays the driving to impose the rate limit.
20. The apparatus of claim 13 , wherein the oscillator generates a signal and the circuit synchronizes the selective coupling in response to a timing of a signal generated by the oscillator.
21. The apparatus of claim 13 , wherein the circuit precharges at least some of the impedances when not coupled to the oscillator.
22. A method comprising:
selectively coupling impedances to an oscillator to establish a first frequency of operation of the oscillator;
repeating the coupling in a feedback loop to cause the first frequency to be near a second frequency of a wireless signal; and
precharging at least some of the impedances when not capacitively coupled to a resonant tank of the oscillator.
23. The method of claim 22 , further comprising:
using the oscillator to generate a signal, wherein
the precharging comprises coupling at least some of the impedances to the signal.