Frequency synthesis device (30; 70) with feedback loop, comprising: - a first control circuit (32; 72) with phase comparison receiving a first reference signal at a reference frequency, a frequency conversion unit (34; 74) voltage controlled by the first control circuit (32; 72) and designed for supplying an output signal at an output frequency that is a multiple of the reference frequency, and a feedback circuit (36; 76) for supplying at least one signal issuing from the frequency conversion unit (34; 74) to the first control circuit (32; 72), - at least one other control circuit (50; 90) receiving at least one other reference signal at the reference frequency for the voltage control of the frequency conversion unit (34; 74) and at least one other feedback circuit (48; 88) for supplying at least one other signal issuing from the frequency conversion unit (34; 74) to this other control circuit (50; 90), characterized in that - said first reference signal and said other reference signal being phase shifted between each other with a predetermined phase shift, - said signals (S1, S2) issuing from the frequency conversion unit (34; 74) being phase shifted between each other with the same predetermined phase shift, wherein each control circuit (32, 50; 72, 90) comprises a phase comparator (38, 52; 78, 92) with two outputs receiving as an input one of the reference signals (SR1, SR2) and the corresponding signal (S1, S2) thereof issuing from the frequency conversion unit (34; 74) supplied by the corresponding feedback loop (36, 48; 76, 88), - each control circuit (32, 50; 72, 90) further comprises a charge pump (40, 54; 80, 94) receiving as an input the outputs of the phase comparator (38, 52; 78, 92) and supplying as an output a control voltage of the frequency conversion unit (34; 74), and - each other control circuit (50; 90) is connected to the first control circuit (32; 72) at the outputs of their respective charge pumps (40, 54; 80, 94) for performing the control voltage of the frequency conversion unit (34; 74) and further comprises means (60; 102) for disconnecting this connection in order to disconnect all the control circuits (50; 90) except the first one (32; 72) from the control voltage of the frequency conversion unit (34; 74), when the engagement phase is over. - a first control circuit (32; 72) with phase comparison receiving a first reference signal at a reference frequency, a frequency conversion unit (34; 74) voltage controlled by the first control circuit (32; 72) and designed for supplying an output signal at an output frequency that is a multiple of the reference frequency, and a feedback circuit (36; 76) for supplying at least one signal issuing from the frequency conversion unit (34; 74) to the first control circuit (32; 72), - at least one other control circuit (50; 90) receiving at least one other reference signal at the reference frequency for the voltage control of the frequency conversion unit (34; 74) and at least one other feedback circuit (48; 88) for supplying at least one other signal issuing from the frequency conversion unit (34; 74) to this other control circuit (50; 90), - said first reference signal and said other reference signal being phase shifted between each other with a predetermined phase shift, - said signals (S1, S2) issuing from the frequency conversion unit (34; 74) being phase shifted between each other with the same predetermined phase shift, - each control circuit (32, 50; 72, 90) further comprises a charge pump (40, 54; 80, 94) receiving as an input the outputs of the phase comparator (38, 52; 78, 92) and supplying as an output a control voltage of the frequency conversion unit (34; 74), and - each other control circuit (50; 90) is connected to the first control circuit (32; 72) at the outputs of their respective charge pumps (40, 54; 80, 94) for performing the control voltage of the frequency conversion unit (34; 74) and further comprises means (60; 102) for disconnecting this connection in order to disconnect all the control circuits (50; 90) except the first one (32; 72) from the control voltage of the frequency conversion unit (34; 74), when the engagement phase is over.