Dual loop frequency synthesizer having fractional dividers
First Claim
1. A frequency synthesizer for providing a first output signal programmable over a first frequency band in first frequency steps and a second output signal programmable over a second frequency band in second frequency steps, comprising;
- first reference divider means for dividing a reference frequency by a first integer to produce a first comparison frequency;
second reference divider means for dividing said reference frequency by a second integer to produce a second comparison frequency;
first controlled oscillator means for producing a first output frequency and having an input for a first frequency control signal;
first fractional-N divider means for dividing said first output frequency by a first programmable quantity having both a first integer part and a first fractional part to produce a first loop frequency;
first phase and frequency comparator means for comparing said first loop frequency with said first comparison frequency to produce a first error signal;
first loop filter means for processing said first error signal to obtain said first frequency control signal;
second controlled oscillator means for producing a second output frequency and having an input for a second frequency control signal;
mixing means for generating a difference frequency signal having inputs from said first and second controlled oscillator means;
second fractional-N divider means for dividing said difference frequency by a second programmable quantity having a second integer part and a second fractional part to produce a second loop frequency;
second phase and frequency comparator means for comparing said second loop frequency with said second comparison frequency to produce a second error signal;
second loop filter means for processing said second error signal to obtain said second frequency control signal.
1 Assignment
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Accused Products
Abstract
A radio telephone which is capable of switching between operating through a land based cellular network and an orbiting satellite system is disclosed. First antenna and radio frequency circuits receive transmitted signals from the land-based network and form first conditioned Signals for subsequent numerical decoding. Second antenna and radio frequency circuits receive transmitted signals from the orbiting satellite system and form second conditioned signals for subsequent numerical decoding. Numerical decoders process either the first conditioned signals or the second conditioned signals to provide an automatic frequency control signal. Reference frequency oscillators controlled by the automatic frequency control signal provide a reference frequency signal. Radio frequency synthesizers using the reference frequency signal and having a first output at a first programmable frequency connected to the first radio frequency circuits determine reception of a channel frequency of the land-based network and a second output at a second programmable frequency connected to the second radio frequency circuits determine reception of a channel frequency of the orbiting satellite system.
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Citations
14 Claims
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1. A frequency synthesizer for providing a first output signal programmable over a first frequency band in first frequency steps and a second output signal programmable over a second frequency band in second frequency steps, comprising;
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first reference divider means for dividing a reference frequency by a first integer to produce a first comparison frequency; second reference divider means for dividing said reference frequency by a second integer to produce a second comparison frequency; first controlled oscillator means for producing a first output frequency and having an input for a first frequency control signal; first fractional-N divider means for dividing said first output frequency by a first programmable quantity having both a first integer part and a first fractional part to produce a first loop frequency; first phase and frequency comparator means for comparing said first loop frequency with said first comparison frequency to produce a first error signal; first loop filter means for processing said first error signal to obtain said first frequency control signal; second controlled oscillator means for producing a second output frequency and having an input for a second frequency control signal; mixing means for generating a difference frequency signal having inputs from said first and second controlled oscillator means; second fractional-N divider means for dividing said difference frequency by a second programmable quantity having a second integer part and a second fractional part to produce a second loop frequency; second phase and frequency comparator means for comparing said second loop frequency with said second comparison frequency to produce a second error signal; second loop filter means for processing said second error signal to obtain said second frequency control signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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Specification