Variable frequency synthesizer with reduced phase noise
AssigneeAdvantest Corporation
InventorTakenori Kurihara
Life of this patent
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Abstract
A reference signal from a reference signal source is supplied to a frequency transformer and a side band signal generator. The frequency transformer is formed mainly by up-converters and produces a frequency m times as high as the frequency f.sub.s of the reference signal. The side band signal generator outputs signals of base and harmonic frequencies f.sub.s, 2f.sub.s, 3f.sub.s, . . . and nf.sub.s (where n is less than m) and produces less phase noise than does the frequency transformer. The outputs of the frequency transformer and the side band signal generator are frequency mixed by a frequency mixer, and one frequency component in the frequency-mixed output is selected by a variable filter.
Claims20
A variable frequency synthesizer comprising:
- a reference signal source for generating a reference signal of a frequency f.sub.s ;
- frequency transforming means supplied with the reference signal from the reference signal source for increasing the frequency of the reference signal, said frequency transforming means including a plurality of up-converters, wherein an output of frequency f.sub.1 =mf.sub.s is produced, where m is an integer equal to or greater than 3;
- side band signal generating means supplied with the reference signal from the reference signal source for outputting n signals of frequencies f.sub.s, 2f.sub.s, 3f.sub.s, . . . and nf.sub.s, wherein n is a positive integer smaller than m, and the degree of generation of phase noise by the side band signal generating means equal to or lower than the degree of generation of phase noise by the frequency transforming means;
- a frequency mixer for frequency mixing the output signals of the side band signal generating means and the output of the frequency transforming means;
- and
- a variable filter for selecting one frequency component (m.+-.n.sub.i)f.sub.s from the output of the frequency mixer, wherein, n.sub.i =0, 1, 2 . . . n.
Dependencies are inferred from the claim text.