Patent ID: 7616066
Filing Date: 2009-11-10
Classification: H03L

Abstract:
1. An oscillation device comprising: a reference oscillation unit for generating an oscillating signal of a specific frequency; a voltage-controlled oscillation unit for generating an output oscillation signal whose frequency is dependent on a control voltage; a phase comparing unit for detecting a phase difference based on the oscillating signal and the output oscillation signal; a digital value storage unit for storing therein a phase difference signal corresponding to the phase difference as a digital value; a sample holding unit for intermittently renewing and maintaining a hold signal in accordance with the digital value; and a control unit for controlling the reference oscillation unit, the phase comparing unit and the digital value storage unit to be started or stopped, and also controlling to employ as the control voltage the phase difference signal or the hold signal, wherein the control unit performs the step of employing as the control voltage the phase difference signal, the step of operating the digital value storage unit after a specific period of time elapses or after the phase difference becomes within a specific range, and the step of employing as the control voltage the hold signal and stopping the reference oscillation unit, the phase comparing unit and the digital value storage unit, wherein the voltage-controlled oscillation unit has a surface acoustic wave oscillator, the digital value storage unit has an A/D converter and a memory, and the sample holding unit has a D/A converter, a capacitor and an analog switch interposed between the D/A converter and the capacitor, and wherein the digital value stored in the digital value storage unit is obtained by filtering the phase difference signal by using a low pass filter.