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US 5,477,197 AGranted
Voltage controlled oscillator with improved voltage versus frequency characteristic
AssigneeAT&T Corp.
InventorShawn M. Logan
Life of this patent
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Abstract
An undesirable relationship between user applied input frequency control voltage and output frequency of a voltage controlled oscillator is counteracted by controlling the characteristics of an amplifier stage in the oscillator as a function of frequency control signal in addition to controlling the output frequency of the oscillator as a function of the capacitance of a user controlled variable capacitance in response to the frequency control signal.
Claims3
A voltage controlled oscillator, comprising:
- a resonator stage having a crystal resonator and a variable capacitance;
- an amplifier having a predetermined gain and input impedance connected to the resonator stage for producing a predetermined output frequency of oscillation;
- a first input for receiving a frequency control signal;
- a means responsive to the first input for applying a drive voltage to the variable capacitance to control its capacitance and the output frequency of oscillation;
- a second input for receiving the frequency control signal;
- a means responsive to the second input for applying a frequency controlling input to the amplifier to create a desired relationship between the magnitude of the frequency control signal and the frequency of oscillation.
3 more elements
A method of controlling an output frequency of a voltage controlled oscillator, comprising the steps of:
- applying a control voltage to a varactor which has a capacitance varying as a function of the magnitude of the control voltage and which influences an output frequency of the voltage controlled oscillator as a function of the magnitude of the control voltage;
- and
- changing the output frequency of the oscillator as a function of the control voltage by changing a predetermined characteristic of an amplification stage in the oscillator to produce a desired output frequency versus control voltage magnitude for the oscillator.
Dependencies are inferred from the claim text.