FRACTIONAL-N METHODS TUNE BASE-STATION SYNTHESIZER

FREQUENCY synthesizers come in many formats, from single-loop, phase-l ocked designs to sophisticated systems combining multiple technologies . In order to meet the requirements of communications base stations fo r good signal-to-noise ratio (SNR) and low phase noise, various synthe sizer technologies were evaluated before arriving at a fractional-N-di vision approach that yields relatively fast switching speeds (on the o rder of 6 mu s) with low phase noise. The technology has been demonstr ated with units operating at 75 to 105 MHz, 700 to 2000 MHz, and 2700 to 3500 MHz.