Apparatus and methods for phase synchronization of phase-locked loops (PLLs) are provided. In certain configurations, an RF communication system includes a PLL that generates one or more output clock signals and a phase synchronization circuit that synchronizes a phase of the PLL. The phase synchronization circuit includes a sampling circuit that generates samples by sampling the one or more output clock signals based on timing of a reference clock signal. Additionally, the phase synchronization circuit includes a phase difference calculation circuit that generates a phase difference signal based on the samples and a tracking digital phase signal representing the phase of the PLL. The phase synchronization circuit further includes a phase adjustment control circuit that provides a phase adjustment to the PLL based on the phase difference signal so as to synchronize the PLL.

A hybrid numeric-analog clock synchronizer, for establishing a clock or carrier locked to a timing reference. The clock may include a framing component. The reference may have a low update rate. The synchronizer achieves high jitter rejection, low phase noise and wide frequency range. It can be integrated on chip. It may comprise a numeric time-locked loop (TLL) with an analog phase-locked loop (PLL). Moreover a high-performance number-controlled oscillator (NCO), for creating an event clock from a master clock according to a period control signal. It processes edge times rather than period values, allowing direct control of the spectrum and peak amplitude of the justification jitter. Moreover a combined clock-and-frame asynchrony detector, for measuring the phase or time offset between composite signals. It responds e.g. to event clocks and frame syncs, enabling frame locking with loop bandwidths greater than the frame rate.

A frequency adjusting apparatus used in a processing chip operated at an operation frequency according to a power is provided that includes a clock supplying circuit, a frequency division circuit and a control circuit. The clock supplying circuit outputs one of clock signals as a supplied clock signal. The frequency division circuit performs frequency division on the supplied clock signal according to a parameter to generate an output clock signal. The control circuit determines a combination of a selected clock signal and a value of the parameter for gradually increasing the frequency of the output clock signal during the increasing of the voltage value that passes through voltage value sections, wherein when the voltage value is determined to be larger than a second threshold value and when the voltage value sections correspond to higher voltage values, the selected clock signal has a higher frequency.

A frequency adjusting apparatus used in a processing chip operated at an operation frequency according to a power is provided that includes a clock supplying circuit, a frequency division circuit and a control circuit. The clock supplying circuit outputs one of clock signals as a supplied clock signal. The frequency division circuit performs frequency division on the supplied clock signal according to a parameter to generate an output clock signal. The control circuit determines a combination of a selected clock signal and a value of the parameter for gradually increasing the frequency of the output clock signal during the increasing of the voltage value that passes through voltage value sections, wherein when the voltage value is determined to be larger than a second threshold value and when the voltage value sections correspond to higher voltage values, the selected clock signal has a higher frequency.

A method for filtering noise. The method may include obtaining an output signal from a phase locked loop (PLL) device. The method may include determining, using a digital phase detector and the output signal, an amount of PLL error produced by the PLL device. The method may include filtering, using a delay element and a digital filter, a portion of the amount of PLL error from the output signal to produce a filtered signal in response to determining the amount of PLL error produced by the PLL device.

A circuit is provided to facilitate temporal redundancy for inter-chip communication. When an inter-chip communication channel fails, data bits associated with the faulty channel are steered to a non-faulty channel and transmitted via the non-faulty channel together with data bits associated with the non-faulty channel at an increased data rate.

A circuit is provided to facilitate temporal redundancy for inter-chip communication. When an inter-chip communication channel fails, data bits associated with the faulty channel are steered to a non-faulty channel and transmitted via the non-faulty channel together with data bits associated with the non-faulty channel at an increased data rate.

A reference frequency calibration module is provided. The reference frequency calibration module includes an oscillator, a frequency divider, a phase-locked loop (PLL) and a frequency-offset calibration unit. The frequency divider couples to the oscillator. The phase-locked loop couples to the frequency divider. The frequency-offset calibration unit couples to the frequency divider and the phase-locked loop. The oscillator is configured for operatively generating an oscillating signal having an oscillating frequency. The frequency divider divides the oscillating signal having the oscillating frequency by a first division parameter to generate a first clock signal having a first reference frequency. The phase-locked loop generates a second clock signal having a second reference frequency according to the first clock signal. The frequency-offset calibration unit is configured for operatively generating the first division parameter according to the second clock signal.

The present invention is directed to data communication. More specifically, embodiments of the present invention provide a transceiver that processes an incoming data stream and generates a recovered clock signal based on the incoming data stream. The transceiver includes a voltage gain amplifier that also performs equalization and provides a driving signal to track and hold circuits that hold the incoming data stream, which is stored by shift and holder buffer circuits. Analog to digital conversion is then performed on the buffer data by a plurality of ADC circuits. Various DSP functions are then performed over the converted data. The converted data are then encoded and transmitted in a PAM format. There are other embodiments as well.

Frequency synthesizers having reduced phase noise and a small step size. One example can provide frequency synthesizers having low phase noise by eliminating dividers in a feedback path and instead employing frequency converters, such as mixers. Step size can be further reduced by providing frequency converters in a reference signal feedforward path. Acquisition time can be decreased by employing a fast-acquisition phase-locked loop that is switched out after acquisition in favor of a low phase-noise phase-locked loop. Another example can reduce phase noise by employing a YIG oscillator. To improve acquisition time, a first, faster phase-locked loop can be used to lock to a signal before switching to a second, slower phase-locked loop that includes the YIG oscillator. Another example can provide low noise by including phase-locked loops that operate in a frequency range having low thermal noise while a frequency of an output signal varies over a wide range.