The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Feb. 21, 2012
Filed:
Apr. 27, 2010
Shih-hao Tarng, Kaohsiung, TW;
Jia-hung Peng, Hsinchu, TW;
Ming-ching Kuo, Chiayi County, TW;
Industrial Technology Research Institute, Hsinchu, TW;
Abstract
An automatic frequency calibration circuit and an automatic frequency calibration method for a fractional-N frequency synthesizer are provided. In a calibration mode, a state machine adjusts a fractional part and an integer part of a division ratio of a frequency divider unit according to a required precision. A first and a second frequency detecting units detect a reference frequency and an output frequency of the frequency divider unit, respectively. A judging interval unit defines at least one judging period in a total comparison time. A comparator compares the outputs of the first and the second frequency detecting units and outputs a comparison result at the judging period. Wherein, the state machine changes the capacitor configuration of a voltage-controlled oscillator when the comparison result shows that the reference frequency does not match the output frequency of the frequency divider unit.