A radio frequency signal synthesizer circuit includes a digital to analog converter configured to generate an analog output signal for each clock cycle of a clock signal to provide the radio frequency signal and a controlled oscillator to generate the clock signal. The controlled oscillator is configured to vary a cycle time of the clock signal for a radio frequency signal in a first frequency range in a first operation mode or to maintain a constant cycle time for a radio frequency signal in a second frequency range in a second operation mode, the second frequency range being different than the first frequency range.