Design of frequency synthesizer based on multiple VCO

This paper introduces a design of frequency synthesizer based on the combination of multi VCO. The combination of multiple VCO can output a wide frequency range of the signal, VCO signal after the decimal frequency divider, and reference signal phase, control VCO error signal obtained, locked. A combination of multiple VCO can improve the phase noise of the output signals, but will bring the loop bandwidth is not consistent, power and other aspects of the problem, through the control of the VCO power supply and variable bandwidth loop filter design, a good solution to the problem. The frequency synthesizer has been successfully applied to portable spectrum analyzer.