A radar level gauge system comprising first pulse generating circuitry for generating a transmission signal, second pulse generating circuitry for generating a reference signal; and frequency control circuitry for controlling the second pulse generating circuitry to achieve a predetermined frequency difference between the transmission signal and the reference signal. The radar level gauge system further comprises first frequency selection circuitry configured to provide a higher order harmonic frequency component of the transmission signal to the frequency control circuitry; and second frequency selection circuitry configured to provide a higher order harmonic frequency component of the reference signal to the frequency control circuitry. The frequency control circuitry is configured to control the second pulse generating circuitry based on the higher order harmonic frequency component of the transmission signal and the higher order harmonic frequency component of the reference signal. Hereby, improved regulation of the reference signal can be achieved substantially without any increase in power consumption of the radar level gauge system.