A fractional-N frequency synthesizer comprising a multi-phase generator, a multi-path error phase generator; a current combiner; a loop filter connected to the current combiner; an oscillator (150) connected to the loop filter; a frequency divider (160); a SDM connected to both the frequency divider and the multi-phase generator, to generate variable division ratio.

A digital synthesizer is described that comprises: a ramp generator configured to generate a signal of frequency control words (FCW), that describes a desired frequency modulated continuous wave; a digitally controlled oscillator (DCO) configured to receive the FCW signal and generate a DCO output signal; a feedback loop comprising a time-to-digital converter (TDC), wherein the feedback loop is configured to feed back the DCO output signal; a phase comparator coupled to the ramp generator and configured to compare a phase of the FCW signal output from the ramp generator with the DCO output signal fed back from the DCO via the feedback loop and output a N-bit oscillator control signal in response thereto. The TDC receives a representation of the DCO output signal and a reference frequency signal to sample the DCO output signal and outputs multiple selectable delays of the DCO output signal. A digital synthesizer circuit sensor is configured to sense an operational condition of the digital synthesizer circuit and select one of the multiple selectable delays output from the TDC in response to the sensed operational condition. A re-timer circuit is coupled to the digital synthesizer circuit sensor and configured to synchronize the selected delayed DCO output signal with the reference frequency signal.

Frequency synthesizer circuitry includes multi-phase clock generator circuitry, frequency divider circuitry, signal retiming circuitry, and signal combining circuitry. The multi-phase clock generator circuitry receives an input clock signal and generates a number of multi-phase clock signals. The frequency divider circuitry also receives the input clock signal and performs frequency division thereon to generate a reference signal. The signal retiming circuitry receives the reference signal and the multi-phase clock signals and generates a number of retiming signals. The signal combining circuitry combines two of the retiming signals to provide an output clock signal that has the same frequency as the reference signal but a different duty cycle.

Various methods provide for trimming the gain in a dual-port phase-locked loop (PLL) of a radio transceiver. Use is made of the radio's demodulator to perform modulation accuracy measurements, thereby reducing the cost and complexity of external test equipment.

A digital synthesizer is described that comprises: a ramp generator configured to generate a signal of frequency control words (FCW), that describes a desired frequency modulated continuous wave; a digitally controlled oscillator (DCO) configured to receive the FCW signal and generate a DCO output signal; a feedback loop comprising a time-to-digital converter (TDC), wherein the feedback loop is configured to feed back the DCO output signal; a phase comparator coupled to the ramp generator and configured to compare a phase of the FCW signal output from the ramp generator with the DCO output signal fed back from the DCO via the feedback loop and output a N-bit oscillator control signal in response thereto. The TDC receives a representation of the DCO output signal and a reference frequency signal to sample the DCO output signal and outputs multiple selectable delays of the DCO output signal. A digital synthesizer circuit sensor is configured to sense an operational condition of the digital synthesizer circuit and select one of the multiple selectable delays output from the TDC in response to the sensed operational condition. A re-timer circuit is coupled to the digital synthesizer circuit sensor and configured to synchronize the selected delayed DCO output signal with the reference frequency signal.

Various methods provide for trimming the gain in a dual-port phase-locked loop (PLL) of a radio transceiver. Use is made of the radio's demodulator to perform modulation accuracy measurements, thereby reducing the cost and complexity of external test equipment.

A circuit for compensating quantized noise in fractional-N frequency synthesizer, comprising a PLL circuit that locks a phase compensated signal to a phase of a reference phase, wherein the phase lock loop circuit comprises a frequency divider and a phase frequency detector; a sigma-delta modulation and phase difference calculator coupled to the frequency divider generating an accumulated phase error by accumulating all previous differences between an input of the frequency divider and an output of the frequency divider within a period; a digital controlled delay line coupled to both the frequency divider and the SDM and Phase Difference calculator and generates the phase compensated signal by multiplying the accumulated phase error with a delay control word; and the phase frequency detector further generates a phase error by comparing the phase compensated signal with the reference clock.

A method and apparatus for performing a two-point calibration of a VCO in a PLL is disclosed. The method includes determining a first steady state tuning voltage of the VCO with no modulation voltage applied. Thereafter, an iterative process may be performed wherein a modulation voltage is applied to the VCO (along with the tuning voltage) and a modified divisor is applied to the divider circuit in the feedback loop. During each iteration, after the PLL is settled, the tuning voltage is measured and a difference between the current value and the first value is determined. If the current and first values of the turning voltage are not equal, another iteration may be performed, modifying at least one of the modulation voltage and the divisor, and determining the difference between the current and first values of the tuning voltage.

Various methods provide for trimming the gain in a dual-port phase-locked loop (PLL) of a radio transceiver. Use is made of the radio's demodulator to perform modulation accuracy measurements, thereby reducing the cost and complexity of external test equipment.

A type I phase locked loop (PLL) includes an oscillator and a feedback path to a phase detector. A first frequency and first relative phase of a first output signal are locked to a frequency and a phase of a first input signal. A second frequency and second relative phase of a second output signal are locked to a frequency and a phase of a second input signal. A correction to the PLL is applied to perform one of: adjusting the second relative phase to equal the first relative phase and adjusting the oscillator frequency.