Method and apparatus for operating a PLL with a phase detector/sample hold circuit for synthesizing high-frequency signals for wireless communications
First Claim
1. A method of operating a frequency synthesizer having a phase locked loop, comprising:
- generating at least one first clock signal, the first clock signal being derived from an output clock signal of phase locked loop;
generating a second clock signal, the second clock signal being derived from a reference clock signal of phase locked loop;
detecting a phase difference between the at least one first clock signal and the second clock signal;
providing a phase difference output signal indicative of the detected phase difference;
sampling and holding the phase difference output signal at timed intervals;
generating at least one control signal from the sampling and holding step; and
controlling the output frequency of a controllable oscillator of the phase locked loop with the at least one control signal.
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Abstract
A method and apparatus for synthesizing high-frequency signals, such as wireless communication signals, includes a phase-locked loop (PLL) frequency synthesizer with a variable capacitance voltage controlled oscillator (VCO) that has a discretely variable capacitance in conjunction with a continuously variable capacitance. The discretely variable capacitance may provide coarse tuning adjustment of the variable capacitance to compensate for capacitor and inductor tolerances and to adjust the output frequency to be near the desired frequency output. The continuously variable capacitance may provide a fine tuning adjustment of the variable capacitance to focus the output frequency to match precisely the desired frequency output. During fine tuning adjustment, the PLL may include an analog control loop in which a phase detector circuit and sample and hold circuit are utilized. The output of the sample and hold circuit may be provided to the PLL VCO as VCO input control signals.
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Citations
20 Claims
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1. A method of operating a frequency synthesizer having a phase locked loop, comprising:
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generating at least one first clock signal, the first clock signal being derived from an output clock signal of phase locked loop; generating a second clock signal, the second clock signal being derived from a reference clock signal of phase locked loop; detecting a phase difference between the at least one first clock signal and the second clock signal; providing a phase difference output signal indicative of the detected phase difference; sampling and holding the phase difference output signal at timed intervals; generating at least one control signal from the sampling and holding step; and controlling the output frequency of a controllable oscillator of the phase locked loop with the at least one control signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification