Phase-locked loop frequency synthesizer with loop gain calibration function

Abstract

The invention discloses a phase-locked loop frequency synthesizer with a loop gain calibration function, including a phase-lock loop and a gain calibration unit. The phase-lock loop is composed of a frequency/phase discriminator, a charge pump, a loop filter, a voltage-controlled oscillator, and a frequency divider; the gain calibration unit is composed of a state machine, a comparator, two analog-digital converter, a reproductive charge pump current source, and a reproductive loop filter resistance R. the invention implements an automatic correction of the loop gain or bandwidth of the frequency synthesizer, the correction is dynamical, elements such as technique, temperature, voltage, longevity and the like are all corrected automatically, its unit structure is simple, a power consumption is low, and the invention is specially suitable for the wireless radio frequency requiring a stable loop gain.

Description

technical field [0001] The invention belongs to the technical field of electronic communication or wireless radio frequency, and particularly relates to a high-performance phase-locked loop frequency synthesizer requiring constant loop gain. Background technique [0002] At present, the phase-locked loop frequency synthesizer is widely used in the field of electronic communication and wireless radio frequency technology, and has become an indispensable module of modern wireless communication. In some systems, the loop gain of the phase-locked loop frequency synthesizer is required to be kept constant. For example, in The loop gain of the phase-locked loop in the GSM system transmitter is required to be constant. Traditional GSM mobile phone transmitters mostly use offset phase-locked loops because of their low noise characteristics. However, with the maturity of sigma-delta modulation technology, at present, phase-locked The loop basically adopts sigma-delta PLL, because it ...

AI Technical Summary

Problems solved by technology

The correction principle is based on the fact that the loop gain is proportional to the product of the charge pump current and the gain of the voltage-controlled oscillator. By segmentally linearizing the gain of the voltage-controlled oscillator, and then performing segmental compensation through the turn-on and turn-off of the charge pump current array, the voltage is obtained. The product of the gain of the voltage-controlled oscillator and the current of the charge pump remains unchanged. The disadvantage of this method is that there are many factors affecting the loop gain. The method in this literature can only compensate the influence of the gain of the voltage-controlled oscillator on the loop gain. The accuracy is directly proportional to the number of segments, but as the number of segments increases, the circuit becomes larger and larger

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