Input-switching voltage-controlled oscillator and PLL-controlled oscillator
First Claim
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1. An input-switching voltage-controlled oscillator, comprising:
- a phase-locked loop (PLL) provided with a variable-voltage capacitance element and a voltage-controlled oscillator;
a source of voltage independent of the variable-voltage capacitance element; and
a switch for selecting one of a plurality of voltages including the variable-voltage capacitance and the independent voltage source in accordance with a selection signal and applying said selected voltage as a control voltage to the voltage-controlled oscillator, wherein when the selection signal is supplied, the switch selects said variable voltage capacitance element as a normal operation mode to operate the voltage-controlled oscillator as a PLL-controlled oscillator.
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Abstract
A PLL-controlled oscillator that can be suitably used for such purposes as a jitter filter in an optical transmission system includes an input voltage-switching control oscillator as a voltage-controlled oscillator (VCO). The input voltage-switching control oscillator includes: an oscillation closed loop that is provided with a variable-voltage capacitance element; and a switch for interchangeably selecting one of a plurality of voltages in accordance with a selection signal and applying the selected voltage as a control voltage to the variable-voltage capacitance element.
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Citations
16 Claims
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1. An input-switching voltage-controlled oscillator, comprising:
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a phase-locked loop (PLL) provided with a variable-voltage capacitance element and a voltage-controlled oscillator;
a source of voltage independent of the variable-voltage capacitance element; and
a switch for selecting one of a plurality of voltages including the variable-voltage capacitance and the independent voltage source in accordance with a selection signal and applying said selected voltage as a control voltage to the voltage-controlled oscillator, wherein when the selection signal is supplied, the switch selects said variable voltage capacitance element as a normal operation mode to operate the voltage-controlled oscillator as a PLL-controlled oscillator. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An input-switching voltage-controlled oscillator comprising:
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a variable-voltage capacitance element to which a control signal is applied;
a capacitor; and
a switch for mutually exclusively selecting one of said variable-voltage capacitance element or said capacitor according to a selection signal and inserting the selected one into an oscillation closed loop. - View Dependent Claims (10)
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11. An input-switching voltage-controlled oscillator comprising:
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a variable-voltage capacitance element to which a control signal is applied;
a capacitor; and
a switch for selecting one of said variable-voltage capacitance element and said capacitor according to a selection signal and inserting the selected one into an oscillation closed loop, wherein said oscillation closed loop includes a crystal unit, said voltage-controlled oscillator is constituted as a voltage-controlled crystal oscillator, and said control voltage is a voltage that is obtained by applying a signal corresponding to a phase difference between a reference signal and an output signal of said voltage-controlled oscillator to a low-pass filter. - View Dependent Claims (12)
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13. A PLL-controlled oscillator comprising:
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a phase comparator for detecting phase difference between a reference signal and an output signal;
a low-pass filter connected to an output of said phase comparator for outputting a control voltage;
an oscillation means for generating said output signal;
a capacitor; and
a selection means for, in accordance with a selection signal, making a transition between a first state in which the oscillation means is caused to oscillate at an output frequency that changes in accordance with said control voltage and a second state in which said oscillation means is caused to oscillate at an output frequency that is regulated by the capacitor and is unaffected by said PLL-control signal, wherein the switch selects mutually exclusively one of the control voltage or the capacitor. - View Dependent Claims (14, 15)
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16. An input-switching voltage-controlled oscillator, comprising:
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a phase-locked loop (PLL) provided with a variable-voltage capacitance element and a voltage-controlled oscillator;
another oscillation closed-loop independent of the PLL, using the voltage-controlled oscillator; and
a switch for selecting one of the PLL or the other loop in accordance with a selection signal and applying the selected voltage as a control voltage to the voltage-controlled oscillator, wherein when the selection signal is supplied, the switch selects the PLL as a normal operation mode to operate the voltage-controlled oscillator as a PLL-controlled oscillator.
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Specification