Control circuit for establishing voltage-controlled or injection-locked operation of a synthesizer reference oscillator
First Claim
1. In a reference oscillator for a frequency synthesizer, the oscillator selectively capable of operation either in an injection-locked mode wherein oscillator operating frequency is determined by the frequency of a crystal-controlled oscillator or in a voltage-controlled mode wherein the oscillator operating frequency is determined by the voltage applied to the oscillator tuning voltage control terminal, the improvement comprising:
- a control circuit for selectively effecting reference oscillator operation in either the injection-locked or voltage-controlled mode, the circuit comprising;
a logic element having an input coupled to a signal source determinative of the desired reference oscillator mode of operation, andan analog gate coupled to the crystal-controlled oscillator and driven by the logic element for selectively coupling the crystal-controlled oscillator to the reference oscillator to establish the injection-locked mode and for isolating the crystal-controlled oscillator from the reference oscillator to establish the voltage-controlled mode.
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Accused Products
Abstract
In a synthesizer system having a reference oscillator selectively operable in either a voltage-controlled or an injection-locked mode, a circuit for effecting the appropriate mode of operation. The circuit includes an analog gate coupled between the output of a crystal oscillator and the input of the reference oscillator. The analog gate is driven by a logic element responsive to a plurality of signals indicative of specific operating conditions. In particular, the circuit assures that the reference oscillator is coupled to the crystal oscillator, that is, the reference oscillator operates in the injection locked mode, while the synthesizer PLL achieves acquisition.
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Citations
18 Claims
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1. In a reference oscillator for a frequency synthesizer, the oscillator selectively capable of operation either in an injection-locked mode wherein oscillator operating frequency is determined by the frequency of a crystal-controlled oscillator or in a voltage-controlled mode wherein the oscillator operating frequency is determined by the voltage applied to the oscillator tuning voltage control terminal, the improvement comprising:
a control circuit for selectively effecting reference oscillator operation in either the injection-locked or voltage-controlled mode, the circuit comprising; a logic element having an input coupled to a signal source determinative of the desired reference oscillator mode of operation, and an analog gate coupled to the crystal-controlled oscillator and driven by the logic element for selectively coupling the crystal-controlled oscillator to the reference oscillator to establish the injection-locked mode and for isolating the crystal-controlled oscillator from the reference oscillator to establish the voltage-controlled mode. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A control circuit for a synthesizer reference oscillator for selectively effecting operation of the oscillator in either a crystal-controlled or a voltage-controlled mode, the circuit comprising:
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a logic element having multiple inputs, at least one of which is connected to a signal indicating the desired oscillator mode of operation, and outputs characterized by opposite polarities, and an analog gate having a first input coupled to an output of the logic element having one polarity and a second input coupled to an output of the logic element having the other polarity, one of the inputs adapted to be connected to a source of crystal oscillator signals so that in the crystal-controlled mode those signals appear at the output of the analog gate but are otherwise inhibited. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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16. In a synthesizer system characterized by a reference oscillator selectively operable in either an injection-locked or voltage controlled mode, an improvement in the form of a control circuit for determining the reference oscillator mode of operation, the circuit comprising:
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first logic means having at least one input coupled to a signal source indicative of a prescribed operating condition; second logic means having an input coupled to an output of the first logic means; and an analog gate having; (1) a first input coupled to the output of the first logic means; (2) a second input coupled to the output of the second logic means; (3) an input coupled to a source of oscillator signal; and (4) an output coupled to the reference oscillator, whereby the analog gate is driven by both logic means in response to the signal source so that the reference oscillator is coupled to the oscillator signal during the injection-locked mode. - View Dependent Claims (17, 18)
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Specification