Asahi Kasei Microdevices Corporation

Other

Cedric Morand

David Canard

Fabrice Jovenin

A phase-locked loop (PLL) device includes synchronization means suitable for synchronizing a frequency-converted signal produced by a frequency divider of the PLL device, with a reference signal supplied to the PLL device. A time duration of a frequency/phase lock acquisition step which is performed upon starting an operation of the PLL device can be reduced. In addition, when operating several PLL devices simultaneously, the synchronization units allow recovering target values for phase differences that exist between the respective frequency-converted signals of the PLL devices. To this end, synchronization is requested at a same time for all the PLL devices after they are all running in locked state.

Phase-locked loop device with synchronization means

A variable modulus sigma delta (&#x3a3;&#x394;) modulator for a fractional-N frequency synthesizer in accordance with the present invention may include an integer division unit; a pulse-width modulation (PWM) generator, a &#x3a3;&#x394; noise-shaping unit, a first input FRAC for receiving a first programmable integer, and a second input MOD for receiving a second input, wherein the integer division unit is configured to perform a translation from the first input and the second input into a first output FRAC' and a second output R, the PWM generator is configured to receive the second input MOD and the second output R, and generate a modulated pulse signal, and the &#x3a3;&#x394; noise-shaping unit is configured to receive the first output and the modulated pulse signal, and generate a sequence whose average equals approximately the first input over the second input.

Variable modulus modulator for fractional-N frequency synthesizers

A fractional-N frequency synthesizer having a cancellation system for phase discontinuity due to loop gain changes may include a phase detector, a current-changeable charge-pump, a loop filter for providing a tuning signal, a voltage-controlled oscillator (VCO) controlled by the tuning signal for providing a VCO output signal, a divider for providing a divided VCO signal, a modulator for generating a modulating signal for fractional-N functionality, wherein the phase detector has a first input for receiving a reference signal oscillating at a reference frequency; a second input for receiving the divided signal; and the phase detector and charge-pump is configured to compare a phase of the first input and a phase of the second input, and generate a charge-pump current on and off, featuring that the cancellation system is implemented inside the modulator having an additional input defined by the changeable charge-pump current values.

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Caen, France

Cedric Morand