Method and apparatus for crystal drift compensation
First Claim
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1. A receiver comprising:
- a time base for generating a reference signal having a reference frequency;
a frequency multiplying circuit for generating an output signal having an output frequency responsive to the reference frequency and a digital frequency command word;
circuitry for adjusting the frequency command word responsive to a variation between the output frequency and a predetermined frequency.
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Abstract
A mobile device includes frequency synthesizer circuitry for generating a channel frequency at a multiple of a reference frequency. The reference frequency is generated by a free-running crystal oscillator, without frequency stabilization circuitry. Variations in the output of the crystal oscillator are compensated by adjusting the multiplication factor of the frequency synthesizer.
13 Citations
34 Claims
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1. A receiver comprising:
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a time base for generating a reference signal having a reference frequency;
a frequency multiplying circuit for generating an output signal having an output frequency responsive to the reference frequency and a digital frequency command word;
circuitry for adjusting the frequency command word responsive to a variation between the output frequency and a predetermined frequency. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A transmitter comprising:
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a time base for generating a reference signal having a reference frequency;
a frequency multiplying circuit for generating an output signal having an output frequency responsive to the reference frequency and a digital frequency command word;
circuitry for adjusting the frequency command word responsive to a variation between the output frequency and a predetermined frequency. - View Dependent Claims (9, 10)
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11. A method of generating an output signal having a predetermined frequency, comprising the steps of:
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generating a reference signal having a reference frequency in a time base;
generating an output signal having an output frequency responsive to the reference frequency and a digital frequency command word;
adjusting the frequency command word responsive to a variation between the output frequency and a predetermined frequency. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18)
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19. A receiver comprising:
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a time base for generating a reference signal having a reference frequency;
control circuitry for controlling the reference frequency of the time base responsive to a frequency correction signal;
a digitally controlled frequency synthesizer for generating an output signal with an output frequency at a multiple of the reference frequency;
circuitry for clocking the control circuitry synchronously with edges of the output signal. - View Dependent Claims (20, 21, 22)
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23. A transmitter comprising:
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a time base for generating a reference signal having a reference frequency;
control circuitry for controlling the reference frequency of the time base responsive to a frequency correction signal;
a frequency synthesizer for generating an output signal with an output frequency at a multiple of the reference frequency;
circuitry for clocking the control circuitry synchronously with edges of the output signal. - View Dependent Claims (24, 25, 26)
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27. A method of generating an output signal having a predetermined frequency, comprising the steps of
generating a reference signal having a reference frequency in a time base; -
controlling the reference frequency of the time base with a control circuit responsive to a frequency correction signal;
generating an output signal with an output frequency at a multiple of the reference frequency in a frequency synthesizer;
clocking the control circuit synchronously with edges of the output signal. - View Dependent Claims (28, 29, 30)
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31. A phase locked loop circuit comprising:
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circuitry for generating an output signal at a frequency multiple of a reference signal, responsive in part to variable phase information associated with a difference between edges of the reference signal and edges of the output signal;
circuitry for sampling the reference signal on both rising and falling edges of the output signal to produce first and second retimed reference signals;
circuitry for selecting from either the first or second retimed reference signal responsive to a metastability control signal;
circuitry for sampling low-order variable phase information on both the first and second retimed reference signals to produce first and second variable phase samples;
circuitry for selecting from either the first or second variable phase samples responsive to a metastability control signal;
circuitry for sampling higher-order variable phase information responsive to the selected retimed reference signal. - View Dependent Claims (32)
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33. A method of generating an output signal as a frequency multiple of a reference signal, responsive in part to variable phase information associated with a difference between edges of the reference signal and edges of the output signal, comprising the steps of:
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sampling the reference signal on both rising and falling edges of the output signal to produce first and second retimed reference signals;
selecting from either the first or second retimed reference signal responsive to a metastability control signal;
sampling low-order variable phase information on both first and second retimed reference signals to produce first and second variable phase samples;
selecting from either the first or second variable phase samples responsive to a metastability control signal;
sampling higher-order variable phase information responsive to the selected retimed reference signal. - View Dependent Claims (34)
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Specification