| 摘要 |
A method for determining the phase shift between two periodic signals having essentially the 1" as a first 0" the two signals into corresponding rectangular voltage waveforms. The interval between homologous edges of the two rectangular waveforms corresponding to the phase difference is converted into a pulse-duration-modulated rectangular signal which is fed to an integrate-and-hold circuit which produces at its output an amplitude-modulated signal proportional to the phase difference that is held for a certain period of time following completion of the integration. A sampling command furnished by a sequence control unit is fed to a sample-and-hold circuit which permits transfer to it of the signal from the output of the integrate circuit. Ahead of the sampling command, the sequence control unit generates a comparison command to a transient detector having a voltage threshold with which there is compared an "old" value of the amplitude-modulated signal corresponding to the last phase difference stored in the sample-and-hold circuit and a "new" value corresponding to the present phase difference at the output of the integrate circuit so that exceeding the threshold level of the detector serves as a criterion for determining a voltage transient corresponding to a 2 pi -transition. Depending upon the result of the comparison, logic " 1" or " 0" signals appear at the outputs of the transient detector which are then fed to, and added in, a reversible counter which thus keeps track of the algebraic sum of the integer 2 pi -transitions.
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