PLL frequency synthesizer

Details PLL frequency synthesizer PLL frequency synthesizer

2007-03-06

2008-07-29

Pascal, Robert J. (Department: 2817)

Oscillators

Automatic frequency stabilization using a phase or frequency...

Plural oscillators controlled

C331S017000, C331S179000

Reexamination Certificate

active

07405627

ABSTRACT:
In a PLL frequency synthesizer outputting signals with different frequencies: voltage-controlled oscillators output the signals and have the oscillation frequencies controlled according to control voltages; a first switch selects one of the signals; a frequency divider generates a frequency-divided signal of the selected signal by use of a changeable frequency-division ratio; a phase comparator generates the phase difference between the frequency-divided signal and a reference signal; a second switch selects one of paths connected to low-pass filters; each low-pass filter is provided for one of the voltage-controlled oscillators, has a changeable time constant, and converts the phase difference into one of the control voltages; and a controller cyclically controls the first and second switches and the frequency divider so that the voltage-controlled oscillators continuously output the signals, and changes the changeable time constant of each low-pass filter after all of the signals become stable.

REFERENCES:
patent: 4510461 (1985-04-01), Dickes et al.
International Search Report dated Dec. 21, 2004 in corresponding Application No. PCT/JP2004/013041.
Patent Abstracts of Japan, Publication No. 07-095069, Published Apr. 7, 1995.
Patent Abstracts of Japan, Publication No. 07-162303, Published Jun. 23, 1995.
Patent Abstracts of Japan, Publication No. 52-027342, Published Mar. 1, 1977.
Patent Abstracts of Japan, Publication No. 63-209223, Published Aug. 30, 1988.
Patent Abstracts of Japan, Publication No. 2004-282223, Published Oct. 7, 2004.

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