| US 7,548,120 B2 | ||
| Frequency switching method | ||
| Tin-Sing Lam, Rowland Heights, Calif. (US); Chao-Tung Yang, Hsinchu (Taiwan); Heng-Chih Lin, Hsinchu (Taiwan); Shou-Fang Chen, Hsinchu (Taiwan); and Sining Zhou, Irvine, Calif. (US) | ||
| Assigned to MStar Semiconductor, Inc., Hsinchu (Taiwan) | ||
| Filed on Aug. 09, 2007, as Appl. No. 11/836,206. | ||
| Claims priority of provisional application 60/821828, filed on Aug. 09, 2006. | ||
| Prior Publication US 2008/0036506 A1, Feb. 14, 2008 | ||
| Int. Cl. H03L 7/00 (2006.01) | ||
| U.S. Cl. 331—2 [331/46; 331/49; 331/179] | 18 Claims |
| 1. A frequency switching method for switching among a plurality of frequency signal sources, each frequency signal source
providing a predetermined frequency range with multiple bands, the method comprising steps of:
a) providing a target frequency data;
b) selecting a first frequency signal source among the frequency signal sources operating to generate a first clock signal;
c) generating a first frequency data according to the first clock signal to compare with the target frequency data;
d) operating the first frequency signal source at the lowest band to generate a second clock signal when the target frequency
data is smaller than the first frequency data; and
e) switching to a second frequency signal source among the frequency signal sources when the target frequency data is greater
than the first frequency data, wherein the second frequency signal source possesses a frequency range higher than that of
the first frequency signal source and operating at the highest band thereof to generate the second clock signal.
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