A circuitry for and a method of generating a frequency modulated radar transmitter signal are provided. The circuitry comprises a modulation signal generator for generating a modulation signal having a waveform describing a required frequency modulation of the frequency modulated radar transmitter signal and comprises a PLL circuitry for generating the frequency modulated radar transmitter signal in dependence of the modulation signal. In the PLL circuitry a controllable frequency divider controls the output frequency of the PLL circuitry in dependence of the modulation signal. The PLL circuitry further comprises a phase detector, a controllable oscillator and possibly a low pass filter. The PLL circuitry further comprises a calibration circuitry being configured to control a parameter of at least one of the phase detector and the controllable oscillator to maintain a loop gain of PLL circuitry.
