Vorrichtung zur Erzeugung eines schwingenden Signals mit einer gewünschten Phasenlage zu einem Eingangssignal

A phase interpolator (70) for generating an output signal (30) phase locked to an input signal (Din) mixes reference oscillating signals (CLK1,CLK2) in variable proportions. The proportions are controlled by control signals derived from an adjustable ring oscillator (72) which is dynamically controlled to give close control of the interpolator. A phase detector (74) compares the phase of said output signal (30) with that of said input signal (Din) to determine whether said signals are in a desired phase relationship and, if not, to output said control signals to achieve the desired phase relationship. The ring oscillator is responsive to the control signals (UP,DOWN) to propagate oscillations in first and second directions around said ring. The frequency of said reference oscillating signals is close to the expected frequency of said input signal whereas the ring oscillator frequency is substantially lower.