Systems and methods provide a fractional signal from a delta sigma modulator to a summer, a combination of an integer value and the fractional signal to a divider, and a divided clock signal from the divider in response to the combination and the input clock signal. The systems and methods also delay the divided clock signal in response to a truncation phase error and gain calibration factor from a calibration unit to provide an output clock signal having equal periods.

A phase locked loop comprises: a controllable oscillator 102; a variable divider arrangement 108, 110 which takes a signal from the controllable oscillator 102 and divides it by a variable amount to provide a lower frequency signal; a sigma-delta modulator 112 arranged to provide a control input to said variable divider arrangement 108, 110; and a phase detector triggered 104 by said lower frequency signal and a reference clock;
wherein said phase locked loop is arranged to be operable in a normal mode in which the controllable oscillator 102 is controlled by a voltage from said phase detector 104 and a calibration mode in which the controllable oscillator 102 is controlled digitally by a signal from a calibration module 114 which receives an input from said variable divider arrangement 108, 110.

The disclosure provides a phase locked loop, PLL, for phase locking an output signal to a reference signal. The PLL comprises a reference path providing the reference signal to a first input of a phase detector, a feedback loop providing the output signal of the PLL as a feedback signal to a second input of the phase detector, a controllable oscillator generating the output signal based on at least a phase difference between reference and feedback signal, a digital-to-time converter, DTC, delaying a signal that is provided at one of the first and second input, a delay calculation path for calculating a DTC delay value. The PLL further comprises a randomization unit for generating and adding a random offset, i.e. a pseudo-random integer, to the delay value. The offset is such that a target output of the phase detector remains substantially unchanged.

A transmitter includes estimation circuitry and correction circuitry. The estimation circuitry is configured to estimate, based at least on a phase error between a local oscillator and a reference frequency, values for parameters that describe a frequency deviation experienced by a phase locked loop (PLL) during transmission of the data sample, wherein the PLL includes a local oscillator. The correction circuitry is configured to generate a correction term based at least on the estimated parameters; adjust the data sample with the correction term to generate a compensated data sample; and provide the compensated data sample for modulation of a carrier wave generated by the local oscillator.

A fractional-N phase locked loop (PLL) and a sliced charge pump (CP) control method thereof are provided. The fractional-N PLL includes a first current source, a first phase frequency detector (PFD), a second current source, a second PFD, and a divided clock controller. The first current source provides a first current. The first PFD generates a first detection signal according to a first divided clock, for controlling the first current source, wherein the first divided clock is generated according to an oscillation clock having an oscillation period. The second current source provides a second current. The second PFD generates a second detection signal according to a second divided clock, for controlling the second current source. The divided clock controller controls the second divided clock based on a variable delay relative to the first divided clock, wherein the variable delay is an integer times the oscillation period.

Performance indicator circuitry is provided for characterizing performance of a phase locked loop (PLL) in a phase path of a polar modulator or polar transmitter that is used to generate a phase modulated RF signal. The PLL includes an oscillator, a high pass path, and a low pass path. The low pass path includes a loop filter. The performance indicator circuitry includes first input circuitry and parameter calculation circuitry. The first input circuitry is configured to input a loop filter signal from the loop filter. The parameter calculation circuitry is configured to compute a value for a performance indicator based on the loop filter signal and control or characterize an aspect of operation of the PLL based on the value.

The purpose of the present invention is to provide a high-power-efficiency and low-design-cost transmission device by implementing, with a constant clock, delta-sigma modulation maintaining a zero current switching property in an amplifier. This delta-sigma modulator comprises: a pulse phase signal generation unit for generating a pulse phase signal from a phase signal; a delta-sigma modulation unit for generating a pulse amplitude signal obtained by delta-sigma modulating an amplitude signal with a constant clock; a phase sorting unit for outputting a control signal on the basis of the phase signal; a delay switching unit for delaying the pulse amplitude signal on the basis of the control signal; and a mixing unit for outputting a pulse string obtained by multiplying together the delayed pulse amplitude signal and the pulse phase signal.

A phase locked loop (PLL) method includes generating a first signal based on a comparison of a phase of a reference clock or signal to a phase of a feedback clock; generating an output clock based on the first signal; generating an intermediate feedback clock including frequency dividing the output clock; fractionally frequency dividing the intermediate feedback clock based on a digital control signal to generate the feedback clock; and generating the digital control signal based on a sampling clock having a frequency greater than a frequency of the feedback clock. In one implementation, a PLL includes a frequency multiplier to generate the sampling clock based on the feedback clock. In another implementation, a PLL uses the intermediate feedback clock as the sampling clock.

A fractional divider processing circuitry is to receive one of a plurality of clock signals as an input clock signal, and generate a first division clock signal based on the input clock signal and a first control signal. Phases of the plurality of clock signals partially overlap each other. The processing circuitry generates a delta-sigma modulation signal based on the first division clock signal and a frequency control word, and generates a second division clock signal based on the plurality of clock signals, the first division clock signal and a second control signal. The second control signal corresponds to a quantization noise of the delta-sigma modulation signal. The processing circuitry generates the second control signal and a digital control word based on the quantization noise of the delta-sigma modulator. The processing circuitry generates a final division clock signal based on the second division clock signal and the digital control word.

An automatic frequency calibration and lock detection circuit includes a frequency error generator circuit, an automatic frequency calibration signal generator circuit, and a lock flag generator circuit. The frequency error generator circuit generates a frequency error signal based on a reference frequency signal and an output frequency signal. The frequency error signal represents a difference between a frequency of the output frequency signal and a target frequency. The automatic frequency calibration signal generator circuit generates an automatic frequency calibration output signal and an automatic frequency calibration done signal based on the frequency error signal and a first clock signal. The lock flag generator circuit generates a lock done signal based on the frequency error signal, the automatic frequency calibration done signal and a second clock signal. The frequency error generator circuit is shared by the automatic frequency calibration signal generator circuit and the lock flag generator circuit.