Importance

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Abstract

In a generator whose frequency can be set digitally and connected in a phase-locked loop (PLL) with a frequency divider whose frequency divider ratio is periodically changed, the sum of the phase errors, which are the phase deviations of the individual frequency-divider delivered pulses from the phase of the reference frequency, is calculated and each pulse for which the phase-error sum exceeds a predetermined value is delayed by a time period corresponding to this value before being fed to the phase meter or phase detector of the phase-locked loop. As a result, any drift or oscillatory fluctuations of the voltage-controlled oscillator (VCO) control voltage are confined to substantially high frequencies and only very weak subharmonic components, and the oscillatory fluctuations can be filtered out easily by a low-pass filter between the phase detector or phase meter and the control-voltage input of the VCO. Also the generation of a compensating voltage is possible using digital means at low cost and with the result that high stability and accuracy of the selected output frequency can be ensured.

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First Claim