Variable frequency synthesizer comprising a sigma-delta...

Details Variable frequency synthesizer comprising a sigma-delta... Variable frequency synthesizer comprising a sigma-delta...

2006-07-25

2006-07-25

Chang, Joseph (Department: 2817)

Oscillators

Automatic frequency stabilization using a phase or frequency...

With reference oscillator or source

C331S014000, C332S128000

Reexamination Certificate

active

07081798

ABSTRACT:
A variable frequency synthesizer comprising a sigma-delta modulator is provided. Such synthesizers provide an exact average frequency whereas the instantaneous frequencies varies. The sigma-delta modulator comprises a plurality of accumulator stages being connected in cascade. At least one input value of an accumulator (51, 52, 53, 54) being part of the sigma-delta modulator has a second component which is equal to an overflow signal (of1, of2, of3, of4) multiplied by a factor. This feedback reduces the-maximum fluctuation of the instantaneous frequencies. Phase jitter generated by non-linearities of the phase detector, the charge pump and the VCO is therefore reduced.

REFERENCES:
patent: 5305362 (1994-04-01), Miller
patent: 6876698 (2005-04-01), Dick et al.
patent: 2002/0061086 (2002-05-01), Adachi et al.
patent: 2003/0058055 (2003-03-01), Sridharan
patent: 0 438 867 (1991-07-01), None
V.F. Kroupa, et al.; “Direct Digital Frequency Synthesizers With The Arrangement in the PLL Systems”; The Iree of the Academy of Sciences of the Czech Republic; pp. 799-805.

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