Frequency synthesizer having multi-band voltage controlled oscillator

摘要

There is provided a frequency synthesizer including a multi-band voltage controlled oscillator having a plurality of voltage controlled oscillating cores outputting oscillation frequencies having different bands according to an input control voltage. Each of the voltage controlled oscillating cores outputs a frequency band divided into a plurality of bands, and the voltage controlled oscillating core operates by each of the divided bands, and one of the voltage controlled oscillating cores operates in one of the bands according to the control voltage. The frequency synthesizer further includes a comparator unit and an oscillation band-determining unit. The comparator unit compares the control voltage with a pre-set reference voltage range. The oscillation band-determining unit changes the band where the voltage controlled oscillating core operates into another one of the bands when the control voltage is out of the pre-set reference voltage range.