FIELD: frequency synthesizers including fractional N frequency synthesizers wherein selected output frequencies are chosen with unwanted frequency drifts reduced. SUBSTANCE: frequency synthesizer has automatic frequency control circuit incorporating programmable frequency divider as well as programmable frequency divider control circuit that has two accumulators. Capacity of two accumulators can be chosen. Bias is selectively entered in accumulators to produce signal of a frequency divided by a fractional number with amplitude of unwanted false subharmonic oscillations maintained below maximum permissible limit as well as in case of permissible frequency drift. EFFECT: improved design. 6 cl, 9 dwg
