A circuit arrangement and a method for obtaining a signal for use in downconverting a signal of a relatively high frequency VCO (7). A pulse train (S 1 ) is generated as a function of a reference signal which is then fed into an oscillator (2) so as to generate a signal (S 2 ) modulated by said pulse train (S 1 ). The resulting signal is fed into a band pass filter (4) which in turn outputs a selected frequency band (S 3 ) to be mixed with the signal of VCO (7) in order to obtain the down converted control signal for phase locking.