US 6,441,692 B1Granted

PLL frequency synthesizer

AssigneeMatsushita Electric Industrial Co., Ltd.

InventorsToshifumi Nakatani, Hisashi Adachi, Hiroaki Kosugi, Yuji Saito, Shunsuke Hirano, Hiroshi Haruki

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Abstract

The invention provides a high-speed PLL frequency synthesizer in which the frequency of a reference signal can be made larger than a frequency interval of an external output with a simple configuration. An n-th harmonic of an output of a voltage-controlled oscillator is caused to pass through a band pass filter. The frequency of an output of the band pass filter is divided by M in a variable frequency divider. The phase of an output of the variable frequency divider is compared with that of the reference signal in a phase comparator. An output of the phase comparator is smoothed by a loop filter. The output of the voltage-controlled oscillator is controlled by an output of the loop filter. The fundamental wave of the output of the voltage-controlled oscillator is caused to pass through another band pass filter, and then output to the outside. At this time, the frequency of the reference signal is n times a frequency interval of the fundamental wave of the output of the voltage-controlled oscillator.

Claims16

Dependent claims

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.

7 more elements

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 said output of said 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-controller 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, and wherein
said synthesizer further comprises a band pass filter or a high-pass filter which allows the n-th harmonic of said output of said voltage-controlled oscillator to pass therethrough to apply the n-th harmonic to said variable frequency divider,
said band pass or high-pass filter does not allow the fundamental wave to pass, and
said band pass or high-pass filter is connected with said voltage-controlled oscillator and is connected with said variable frequency divider.

7 more elements

A PLL frequency synthesizer comprising;

a voltage-controlled oscillator providing a fundamental wave and harmonics thereof as an output, said voltage controlled oscillator being controlled by a control signal;
an external output that provides said fundamental wave as the output from said synthesizer;
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 fundamental wave of said voltage-controlled oscillator, and
wherein in said variable frequency divider, a lowest input power at which a frequency division is enabled at a frequency of said n-th harmonic component of said output of said voltage-controlled oscillator is smaller than a lowest input power at which a frequency division is enabled at a frequency of the fundamental wave of said output of said voltage-controlled oscillator.

5 more elements

Dependencies are inferred from the claim text.