Abstract: A frequency synthesizer employs a combination of a low divide ratio divider phase-locked loop (PLL) and a wide band, on-chip voltage-controlled oscillator (VCO). To reduce phase noise, low divide ratio phase detection is employed. By using the off-chip PLL with a bank of on-chip VCOs, the frequency synthesizer may have enhanced frequency stability and avoid having to include an acquisition circuit. A separation between the PLL and VCO may reduce integer boundary spurs (IBS) eliminating or reducing a need for a filter bank and switches reducing a complexity of the frequency synthesizer.

Abstract: A wide band frequency synthesizer may include a primary phase-locked loop (PLL) to receive a signal that include a local signal and a VCO signal mixed together and to generate the tuning voltage based on a phase comparison of the local signal and the VCO signal. The local signal may be obtained from a reference signal through frequency multiplication. If the primary PLL fails to lock onto an output frequency, a secondary PLL (acquisition circuit) may be switched in performing a phase comparison between the reference signal and the VCO signal to generate the tuning voltage. The secondary PLL may then provide the tuning voltage to an output of the primary PLL.