Skyworks Solutions, Inc.

Ardeshir Namdar-Mehdiabadi

John William Mitchell Rogers

Darren Roger Frenette

Rachel Katumba

Thomas Obkircher

Tudor Lipan

Yong Hee Lee

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.

Circuits and methods for eliminating reference spurs in fractional-N frequency synthesis

Disclosed are systems and method for controlling frequency synthesizers. A control system can be implemented in a phase-locked loop (PLL), such as a Frac-N PLL of a frequency synthesizer, to reduce or eliminate reference spurs. In some embodiments, such a control system can include a phase detector configured to receive a reference signal and a feedback signal. The phase detector can be configured to generate a first signal representative of a phase difference between the reference signal and the feedback signal. The control system can further include a charge pump configured to generate a compensation signal based on the first signal. The control system can further includes an oscillator configured to generate an output signal based on the compensation signal. The compensation signal can be configured to reduce or substantially eliminate one or more reference spurs associated with the frequency synthesizer.

Methods related to frequency synthesis control

Systems and methods for controlling frequency synthesis

Apparatus and methods for detecting a lock in a phase-locked loop (PLL) are disclosed. In one aspect, a lock detect component includes a reference multiplier and a lock detect. The reference multiplier can receive a reference signal, a divider signal, and a voltage-controlled oscillator (VCO) output generated by a VCO in a PLL from which the divider signal is generated. The reference multiplier can also generate a multiplied reference signal using the reference signal and the VCO output. The multiplied reference signal can have a frequency that is an integer multiple of a frequency of the reference signal. The lock detect can detect a phase lock of the reference signal and the divider signal based at least in part on comparing a signal generated from a delayed reference signal and a signal generated from a delayed divider signal for a predetermined period of time.

Phase-locked loop lock detect

An (N&#x2212;1)/N prescaler is provided, where N is an S power of 2. The prescaler uses only S flip-flops. The (N&#x2212;1)/N prescaler receives a clock input from a high frequency oscillator, and provides an output line to a counter. The (N&#x2212;1)/N prescaler receives a divide-by-(N&#x2212;1) signal from the counter, and responsive to the divide signal, causes the prescaler to divide by a factor of (N&#x2212;1); otherwise, the prescaler divides by a factor of N.

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Ottawa, Canada

Ardeshir Namdar-Mehdiabadi