A clock generation circuit for generating an RF clock signal, the clock generation circuit comprising: a pattern generator to generate a pre-distorted version of a modulation signal from digital patterns stored by the pattern generator; an up-converter to mix the pre-distorted version of the modulation signal and a radio frequency local oscillator signal to generate a first signal having a wanted tone corresponding to a desired frequency; a notch filter to filter the first signal and provide the RF clock signal, wherein the notch filter is constructed to suppress a third order harmonic tone of the first RF clock signal to prevent additional modulation tones introduced by a following clock driver or clock divider; a tone detection circuit to receive the RF clock signal and to detect both amplitudes and phases corresponding to a presence of unwanted tones in the RF clock signal, where the tone detection circuit includes: a first mixer to receive the RF clock signal as an input signal and down-convert the input signal based on the radio frequency local oscillator signal; and a second mixer to convert the down converted input signal to a signal that includes a baseband representation of one of the unwanted tones; a controller to generate pre-distortion data based on the detected amplitudes and phases and control the pattern generator to generate the pre-distorted version of the modulation signal based on the pre-distortion data, characterized in that the controller controls the tone detection circuit to sequentially detect the presence of a plurality of the unwanted tones in the RF clock signal by a variable signal at a selectable frequency of n-times a modulation signal frequency of the modulation signal, the variable signal being input to the second mixer of the tone detection circuit where the variable signal has frequencies at n:th harmonic of the modulation signal frequency n is an integer and the value of n is sequentially varied by the controller to perform tone detection for the different modulation signal frequency harmonics. a pattern generator to generate a pre-distorted version of a modulation signal from digital patterns stored by the pattern generator; an up-converter to mix the pre-distorted version of the modulation signal and a radio frequency local oscillator signal to generate a first signal having a wanted tone corresponding to a desired frequency; a notch filter to filter the first signal and provide the RF clock signal, wherein the notch filter is constructed to suppress a third order harmonic tone of the first RF clock signal to prevent additional modulation tones introduced by a following clock driver or clock divider; a tone detection circuit to receive the RF clock signal and to detect both amplitudes and phases corresponding to a presence of unwanted tones in the RF clock signal, where the tone detection circuit includes: a first mixer to receive the RF clock signal as an input signal and down-convert the input signal based on the radio frequency local oscillator signal; and a second mixer to convert the down converted input signal to a signal that includes a baseband representation of one of the unwanted tones; a controller to generate pre-distortion data based on the detected amplitudes and phases and control the pattern generator to generate the pre-distorted version of the modulation signal based on the pre-distortion data, characterized in that the controller controls the tone detection circuit to sequentially detect the presence of a plurality of the unwanted tones in the RF clock signal by a variable signal at a selectable frequency of n-times a modulation signal frequency of the modulation signal, the variable signal being input to the second mixer of the tone detection circuit where the variable signal has frequencies at n:th harmonic of the modulation signal frequency n is an integer and the value of n is sequentially varied by the controller to perform tone detection for the different modulation signal frequency harmonics. a first mixer to receive the RF clock signal as an input signal and down-convert the input signal based on the radio frequency local oscillator signal; and a second mixer to convert the down converted input signal to a signal that includes a baseband representation of one of the unwanted tones; a controller to generate pre-distortion data based on the detected amplitudes and phases and control the pattern generator to generate the pre-distorted version of the modulation signal based on the pre-distortion data, characterized in that the controller controls the tone detection circuit to sequentially detect the presence of a plurality of the unwanted tones in the RF clock signal by a variable signal at a selectable frequency of n-times a modulation signal frequency of the modulation signal, the variable signal being input to the second mixer of the tone detection circuit where the variable signal has frequencies at n:th harmonic of the modulation signal frequency n is an integer and the value of n is sequentially varied by the controller to perform tone detection for the different modulation signal frequency harmonics.