| 摘要 |
PURPOSE:To realize acquistion at a high speed and to reduce jitters caused after the acquistion, by varying the number of stages of a random walk filter contained in a phase locked loop and adding a random walk filter which controls the above-mentioned number of stages. CONSTITUTION:A random walk filter 2A has the up-random, stay random and down-random walk actions in response to the plus, zero and minus of the output P(n) of a phase detector 1. If the result of this walk action is equal to the stage number N(n) of a time point (n), phase advancing information is fed to a VCO3. Phase delaying information is fed if the result is equal to the stage number -N(n). Otherwise the state maintenance information is fed, respectively. The VCO3 changes the phase of the output signal by the information Q1(n). A control random walk filter 2B performs a random walk action by the information Q1(n). If the result of this walk action is equal to the stage number N2 and -N2, the information indicating a reduction of the stage number N(n) of the filter 2A is fed. Otherwise the information indicating the maintenance of the stage number is fed. |
