Hybrid AFC using DCXO and RF PLL
AssigneeBroadcom Corporation
InventorsRami Mehio, Masoud Kahrizi, Cobus de Beer, Michael Buyanin
Life of this patent
Estimating the term…
Abstract
A technique to provide hybrid compensation to correct for drifts in a reference frequency output from a digitally-controlled crystal oscillator (DCXO). A first compensation is provided to the DCXO to adjust for overlap or discontinuity of the reference frequency caused by switching capacitors in the capacitor array that controls drift of the reference frequency output. The second compensation is obtained at a phase-locked loop (PLL) that receives the reference frequency signal from the DCXO. The second compensation adjusts the PLL to adjust for variations of the reference frequency that remain after performing compensation in the DCXO.
Claims20
An apparatus comprising:
- a digitally-controlled oscillator (DCXO) to generate a reference frequency signal, the DCXO including a capacitor array configured to adjust the reference frequency signal by switching in and out capacitors of the capacitor array to compensate for drift in the reference frequency signal;
- a local oscillator coupled to receive the reference frequency signal and to provide an output signal based on the reference frequency signal;
- and
- a frequency correction module, coupled to the DCXO and to the local oscillator, to provide a first compensation signal to control the capacitor array and to provide a second compensation signal to the local oscillator to adjust for variations of the reference frequency signal remaining in the reference frequency signal after performing compensation in the digitally-controlled oscillator.
An apparatus comprising:
- a digitally-controlled crystal oscillator (DCXO) to generate a reference frequency signal, the DCXO including a capacitor array configured to adjust the reference frequency signal by switching in and out capacitors of the capacitor array to compensate for drift in the reference frequency signal;
- a phase-locked loop (PLL) coupled to receive the reference frequency signal and to provide an output signal based on the reference frequency signal;
- and
- a frequency correction module, coupled to the DCXO and the PLL, to provide a first compensation signal to the capacitor array to compensate for drift of the reference frequency signal by selecting capacitors of the capacitor array, in which the first compensation signal also to adjust for overlap or discontinuity of the reference frequency signal caused by switching capacitors in the capacitor array, the frequency correction module to also provide a second compensation signal to the PLL to adjust for variations of the reference frequency signal remaining in the reference frequency signal after performing compensation for the DCXO in the capacitor array.
A method comprising:
- providing a first compensation signal from a frequency correction module to a capacitor array of a digitally-controlled crystal oscillator (DCXO) to compensate for drift of a reference frequency signal generated by the DCXO by selecting capacitors of the capacitor array, in which the first compensation signal also to adjust for overlap or discontinuity of the reference frequency signal caused by switching capacitors in the capacitor array;
- and
- providing a second compensation signal from the frequency correction module to a phase-locked loop (PLL) that receives the reference frequency signal from the DCXO to adjust for variations of the reference frequency signal remaining in the reference frequency signal after performing compensation for the DCXO by the capacitor array.
Dependencies are inferred from the claim text.