VARIABLE PHASE SHIFT CIRCUIT, PHASE INTERPOLATOR WITH THE SAME INTEGRATED THEREIN, AND DIGITAL FREQUENCY SYNTHESIZER WITH SUCH INTERPOLATOR INTEGRATED THEREIN

摘要

PROBLEM TO BE SOLVED: To provide a variable phase shift circuit having characteristics suitable for a use in a phase interpolator.

SOLUTION: The variable phase shift circuit is provided with: an input A for inputting an input signal Sin having a designated oscillation frequency; an output B for supplying an output signal Sout having the same oscillation frequency as the input signal and having a variable phase shift to the input signal; and at least one control input C. The control input C inputs a control signal Is for controlling the phase shift of the output signal corresponding to the input signal. The circuit includes a synchronous oscillator OS having a synchronous input in1 connected to the input of the variable phase shift circuit for inputting the input signal Sin and at least one output out1 connected to the output of the phase shift circuit for outputting the output signal Sout. The synchronous oscillator OS has a variable free-running oscillation frequency which is controlled by the control signal Is.

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