Patent ID: 6441692
Filing Date: 2002-08-27
Classification: H03L

Abstract:
A PLL frequency synthesizer comprising:a voltage-controlled oscillator providing a fundamental wave component and harmonics thereof at an output, said voltage controlled oscillator being controlled by a control signal; an external output, connected with an output of the voltage-controlled oscillator, said external output providing an output signal as the output of said synthesizer wherein an n-th harmonic component of the output signal has a smaller power than that of the fundamental wave component of said voltage-controlled oscillator; a variable frequency divider which divides an n-th harmonic of said output of said voltage-controlled oscillator; a phase comparator which compares a phase of a reference signal with a phase of an output of said variable frequency divider; and a loop filter which smooths an output of said phase comparator to output the smoothed output as said control signal for said voltage-controlled oscillator, wherein a frequency of said reference signal is n times a frequency interval of said external output, said synthesizer further comprises an amplifier which selectively amplifies the n-th harmonic of said output of said voltage-controlled oscillator to output the amplified n-th harmonic to said variable frequency divider, said amplifier does not allow the fundamental wave to pass, and said amplifier is connected with said voltage-controlled oscillator and is connected with said variable frequency divider.