Method and arrangement for frequency synthesis

Details Method and arrangement for frequency synthesis Method and arrangement for frequency synthesis

1991-12-10

1993-01-19

Mis, David

Oscillators

Automatic frequency stabilization using a phase or frequency...

Tuning compensation

331 1A, 331 17, 331 25, 455260, H03L 7197

Patent

active

051809931

ABSTRACT:
In a fractional-N frequency synthesizer, the phase error signal is amplified with a factor N prior to adding or subtracting the correction value. This procedure is simpler than the procedure of multiplying the correction value by the factor 1/N. For instance, the phase error signal can be amplified in a separate means, such as an analogue multiplier or a multiplying digital-analogue converter. Amplification can also be effected in conjunction with forming the phase error signal, e.g., by amplifying currents in a so-called charging pump. Amplification of the phase error signal also affords the advantage that loop amplification, loop damping factor and loop band width are held constant. These parameters would otherwise be dependent on 1/N, as a result of varying the frequency. The foregoing technique may also be applied in conjunction with a further technique that allows the loop bandwidth of the frequency synthesizer to be varied. Proportional and integral control currents are produced and compensated for fractional-N ripple and are applied to different input points on a loop filter to obtain an output voltage to control the frequency of a voltage controlled oscillator.

REFERENCES:
patent: 4935707 (1990-06-01), Irwin

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