out by the delta sigma modulator 24 after each period of the reference frequency for an integer n division the same set of division ratio control signals will be selected after each period of the reference frequency f ref a respective set comprising one control signal for each divider cell 26 1 to 26 n for a fractional n division a new set of division ratio control signals will be selected after each period of the reference frequency f ref the switching between different sets of division ratio control signals in the system of fig2 during a fractional n division will now be described with reference to the flow chart of fig3 the divider chain starts off with dividing the frequency of a signal f in received by the radio frequency generator 23 with a first set of division ratio control signals p 0 to p n 1 step 301 the first set of division ratio control signals p 0 to p n 1 can be for example a default set in the case of a fractional n division the delta sigma modulator 24 outputs varying sets of division ratio control signals p 0 to p n 1 with each period of the reference frequency f ref a respectively new set of division ratio control signals p 0 to p n 1 is not provided directly to the programming inputs of the divider cells 26 1 to 26 n though instead each division ratio control signal p x 1 of a new set of control signals p 0 to p n 1 is provided to the latch 27 x having a corresponding ordinal number x step 302 each latch 27 1 to 27 n buffers the received division ratio control.