Patent ID: 6947510

Claim:
A circuit for generating an output phase signal with a variable phase shift relative to a reference phase, including an oscillator outputting phase signals at n outputs, each of which is shifted in phase by φ=360°/n from one output to the next and is correspondingly staggered in time relative to each other by Δt, a first multiplexer, the inputs of which are connected to the even-number outputs of the oscillator and which passes on to its output a phase signal output by an output x of the oscillator as a function of a phase selection signal output by a phase select circuit, where x is a selected one of the n outputs of the oscillator, a second multiplexer, the inputs of which are connected to the odd-number outputs of the oscillator and which passes to its output on a phase signal output by an output x +1 of the oscillator as a function of a second phase selection signal output by the phase select circuit, a phase interpolator receiving the phase signals output by the multiplexers and controlling with these the periodic opening and closing of a first set of phase switches in the time spacing of Δt, the phase interpolator containing a first charging circuit in which a charging voltage of a capacitor is varied by switching current sources assigned to the first set of phase switches on or off in accordance with the closing or opening of the first set of phase switches, whereby a number of current sources is provided corresponding to the number of interphase shift values to be generated between the phase shifts of the phase signals output by the first and second multiplexers, to each of which at least two phase switches are assigned, of which the one in each case is controlled by the phase signal output by the first multiplexer and the other by the phase signal output by the second multiplexer, a first separating switch being inserted in the connection between a first of the at least two phase switches and the assigned current source, an a second separating switch being inserted in the connection between a second of the at least two phase switches, thereby providing a first set and a second set of separating switches for said number of current sources, characterized in that in each connection between each of said first phase switches and the first charging circuit a third separating switch is inserted, and in each connection between each of said second phase switches a fourth set of separating switches is inserted, thereby providing a third set and a fourth set of separating switches, and that a control circuit is provided for each current source which ensures that the first set and the third set of separating switches assigned to each phase switch operate in a first phase, and the second set and the fourth set of separating switches assigned to the same phase switch operate in a second phase reverse to the first phase, and are activated to switch the separating switches for the current sources in a cycling sequence when there is a change in the phasing of the output phase signal relative to the reference phase.