Phase shifting circuit having a constant phase shift
AssigneeNEC Electronics Corporation
InventorKatsuji Kimura
Life of this patent
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Abstract
Disclosed is a phase shifting circuit that includes a PLL loop in which a reference frequency received is branched into first and second signals. The first signal becomes one input to a phase comparator and the second signal becomes another input to the phase comparator after being shifted in phase via a phase shifter. The output of the phase comparator is supplied to one input terminal of a differential amplifier via a low-pass filter. The amount of phase shift of the phase shifter is controlled by the output signal of the differential amplifier. The amount of phase shift of the phase shifter is decided by a reference voltage applied to another input terminal of the differential amplifier.
Claims19
A phase shifting circuit, comprising:
- a phase-locked loop (PLL loop) in which a reference frequency signal is received and branched into first and second signals, said PLL loop including:
- a phase comparator comprising a first comparator input terminal for receiving the first signal and a second comparator input terminal;
- a phase shifter that receives the second signal and phase-shifts the second signal to output a phase-shifted signal, the phase-shifted signal output from said phase shifter being supplied to the second comparator input terminal of said phase comparator;
- a low-pass filter that receives an output signal from said phase comparator;
- a differential amplifier comprising a first amplifier input terminal connected to an output of said low-pass filter and a second amplifier input terminal;
- and
- first and second frequency dividers that divide frequency by mutually identical numbers, said first and second frequency dividers being inserted in front of respective ones of the first and second input terminals of said phase comparator,
- wherein an amount of phase shift by said phase shifter is controlled by an output signal from said differential amplifier, the amount of phase shift by said phase shifter being decided by a reference voltage applied to the second amplifier input terminal of said differential amplifier.
A phase shifting circuit, comprising a phase-locked loop (PLL loop) that includes:
- a first phase shifter that receives a reference frequency signal and phase-shifts the reference frequency signal to output a phase-shifted signal, the first phase-shifted signal output from said first phase shifter being branched into first and second signals;
- a phase comparator comprising a first comparator input terminal for receiving the first signal and a second comparator input terminal;
- a second phase shifter that receives the second signal and phase-shifts the second signal to output a second phase-shifted signal, the second phase-shifted signal output from said second phase shifter being supplied to the second comparator input terminal of said phase comparator;
- a low-pass filter that receives an output signal from said phase comparator;
- and
- a differential amplifier comprising a first amplifier input terminal connected to an output of said low-pass filter and a second amplifier input terminal,
- wherein amounts of phase shift by said first and second phase shifters are controlled by an output signal from said differential amplifier, the amounts of phase shift by said first and second phase shifters being decided by a reference voltage applied to the second amplifier input terminal of said differential amplifier.
A phase shifting circuit, comprising a phase-locked loop (PLL loop) that includes:
- a phase comparator comprising a first comparator input terminal, for receiving a reference frequency signal, and a second comparator input terminal;
- a voltage-controlled oscillator, an oscillation frequency of which is varied by a control voltage applied thereto, an output signal from said voltage-controlled oscillator being supplied to the second comparator input terminal of said phase comparator;
- a low-pass filter that receives an output signal from said phase comparator;
- and
- a differential amplifier comprising a first amplifier input terminal connected to an output of said low-pass filter and a second amplifier input terminal,
- wherein the oscillation frequency of said voltage-controlled oscillator is controlled by an output signal from said differential amplifier, the amount of phase shift by said phase shifter being decided by a reference voltage applied to the second amplifier input terminal of said differential amplifier.
Dependencies are inferred from the claim text.