CIRCUITS AND METHODS FOR ELIMINATING REFERENCE SPURS IN FRACTIONAL-N FREQUENCY SYNTHESIS
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Abstract
Disclosed are circuits and method for reducing or eliminating reference spurs in frequency synthesizers. In some implementations, a phase-locked loop (PLL) such as a Frac-N PLL of a frequency synthesizer can include a phase frequency detector (PFD) configured to receive a reference signal and a feedback signal. The PFD can be configured to generate a first signal representative of a phase difference between the reference signal and the feedback signal. The PLL can further include a compensation circuit configured to generate a compensation signal based on the first signal. The PLL can further includes a voltage-controlled oscillator (VCO) configured to generate an output signal based on the compensation signal. The compensation signal can include at least one feature for substantially eliminating one or more reference spurs associated with the PLL.
6 Citations
21 Claims
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1. (canceled)
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2. A circuit comprising:
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a phase frequency detector (PFD) configured to receive a reference signal and a feedback signal, the PFD further configured to generate a first signal based on the reference signal and the feedback signal; and a compensation circuit configured to receive the first signal, the compensation circuit including a charging circuit, a charge pump, and a voltage-to-current converter positioned between the charging circuit and the charge pump, the compensation circuit further configured to generate a compensation signal based on the received first signal. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A method comprising:
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receiving a reference signal and a feedback signal; generating a first signal based on the reference signal and the feedback signal; and with a compensation circuit including a charging circuit, a charge pump, and a voltage-to-current converter positioned between the charging circuit and the charge pump, generating a compensation signal based on the generated first signal.
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21. A wireless device comprising:
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an antenna configured to facilitate reception of a radio-frequency (RF) signal; a receiver in communication with the antenna, the receiver configured to process the RF signal; and a frequency synthesizer in communication with the receiver, the frequency synthesizer circuit having a circuit including a phase frequency detector (PFD) configured to receive a reference signal and a feedback signal, the PFD further configured to generate a first signal based on the reference signal and the feedback signal, the circuit further including a compensation circuit configured to receive the first signal, the compensation circuit including a charging circuit, a charge pump, and a voltage-to-current converter positioned between the charging circuit and the charge pump, the compensation circuit configured to generate a compensation signal based on the first signal.
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Specification