A broadband phase-shifting circuit, in particular for an IQ modulator, has two phase-shifting branches connected in parallel, to the input of which is supplied the input signal of which the phase is to be shifted, and which supply at their outputs output signals of which the phase is shifted over a predetermined angle, in particular of 90°. The phase shifter of one phase-shifting branch is controlled depending on the frequency of the input signal in such a way that the phase angle between the two output signals approximately corresponds to the desired value (coarse control), whereas the phase shifter of the other phase-shifting branch is set to the desired phase angle (fine regulation by a phase detector connected between the outputs of the two phase-shifting branches.
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