A 57 GHz programmable frequency divider for fractional-N frequency synthesizers

A programmable frequency divider for the use in a fractional-N frequency synthesizer is presented. The measured input frequency range is from DC to 57 GHz for division factors in the entire integer range between 12 and 259 as well as 8 and 9. The frequency divider is based on a dual-modulus concept and has been realized in a SiGe bipolar technology (fT/fmax=170/250 GHz). The exceedingly high maximum input frequency has been reached by using emitter-coupled differential circuit technique with a consequent merging of logic operations and D flip-flops. The divider is designed for low power consumption of less than 300mW at a supply voltage of 3.3V. For the intended use in a fractional-N frequency synthesizer for the millimeter wave range, the division ratio is programmable via an 8 bit parallel interface to enable fast modulation of the division factor.