US 8,138,844 B1Granted

System and method for crystal oscillator frequency tuning

AssigneeFujitsu Semiconductor Limited

InventorsJohn Simmons, Kristopher Kaufman

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Abstract

An oscillator may include a crystal resonator, an inverter coupled in parallel with the crystal resonator, a first switched capacitor coupled to a first terminal of the crystal resonator, a second switched capacitor coupled to a second terminal of the crystal resonator, a control module configured to output a periodic dithering signal, the periodic dithering signal having a first pulse width based on a desired frequency of oscillation for the oscillator, and a delay module configured to communicate a first periodic enable signal to enable the first switched capacitor and a second periodic enable signal to enable the second switched capacitor. At least one of the first periodic enable signal and the second periodic enable signal may have a second pulse width greater than the first pulse width. The second periodic enable signal may be phase delayed relative to the first periodic enable signal by a non-zero delay.

Claims18

Dependent claims

A wireless communication element, comprising:

at least one of:
a receive path configured to receive a first wireless communication signal and convert the first wireless communication signal into a first digital signal based at least on an oscillator signal;
and
a transmit path configured to convert a second digital signal into a second wireless communication signal based at least on the oscillator signal and transmit the second wireless communication signal;
and
an oscillator configured to output the oscillator signal to at least one of the receive path and the transmit path, the oscillator comprising:
a crystal resonator;
an inverter coupled in parallel with the crystal resonator;
a first switched capacitor coupled to a first terminal of the crystal resonator;
a second switched capacitor coupled to a second terminal of the crystal resonator;
a control module configured to output a periodic dithering signal, the periodic dithering signal having a first pulse width based on a desired frequency of oscillation for the oscillator;
and
a delay module configured to communicate a first periodic enable signal to enable the first switched capacitor and a second periodic enable signal to enable the second switched capacitor, such that:
at least one of the first periodic enable signal and the second periodic enable signal have a second pulse width greater than the first pulse width;
and
the second periodic enable signal is phase delayed relative to the first periodic enable signal by a non-zero delay.

13 more elements

Dependencies are inferred from the claim text.