| 摘要 |
A broad band frequency synthesizer is provided to improve phase noise by installing a plurality of frequency down-converting mixers between a voltage controlled oscillator and a programmable 1/N frequency divider. A high-frequency phase locked loop(520) includes a programmable 1/N frequency divider(526), a high-frequency phase detector(522), a charge pump(523), a high-frequency loop filter(524), and a voltage controlled oscillator(525). A low-frequency phase locked loop(530) includes a programmable 1/N frequency divider(536), a low-frequency phase detector(532), a charge pump(533), a low-frequency loop filter(534), and a voltage controlled oscillator(535). A direct oscillator(510) applies a reference frequency to each of the phase detectors. A switching unit(540) is installed between an output terminal of each voltage controlled oscillators and each frequency divider. A frequency mixer(550) is installed between the switching unit and the low-frequency phase locked loop in order to divide an output signal of each voltage controlled oscillators and remove a spurious signal. |
