Method and device for determining whether phase-locked loop is locked

Abstract

The embodiments of the invention provide a method and a device for determining whether a phase-locked loop is locked. The method includes the following steps: detecting a UP pulse and a DOWN pulse output by a phase detector of a phase-locked loop, and subtracting the DOWN pulse from the UP pulse to get a net phase; and determining whether the width of the net phase is smaller than a set locking judgment threshold, and if the width of the net phase is smaller than the set locking judgment threshold, determining that the phase-locked loop is locked. A digital detection technology is adopted in the embodiments of the invention. The UP pulse and the DOWN pulse output by the phase detector are sampled, the net phase is obtained by subtracting the DOWN pulse from the UP pulse, and whether the phase-locked loop is locked is determined according to the width of the net phase. By increasing the VCO (Voltage Controlled Oscillator) frequency of the phase-locked loop, the problem on how to detect a digital narrow pulse precisely is solved.

Description

technical field [0001] The invention relates to the technical field of phase-locked loops, in particular to a method and a device for judging the locking state of the phase-locked loop. Background technique [0002] The function of PLL (Phase-Locked Loop) is to make the phase of the clock on the circuit the same as that of an external clock. The phase-locked loop is a typical feedback control circuit, which uses the reference signal input from the outside to control the loop internal The frequency and phase of the oscillating signal realize automatic tracking of the frequency of the output signal to the frequency of the input signal. Phase-locked loops are generally used in closed-loop tracking circuits, which is a method to stabilize the frequency in radio transmission. [0003] In the practical application of the phase-locked loop, it is necessary to perform lock detection on the phase-locked loop. At present, the first locking detection method of the phase-locked loop i...

AI Technical Summary

Problems solved by technology

[0006] The disadvantage of the lock detection method of the above-mentioned second phase-locked loop is: the judgment method is simple, and the result of the judgment is only two cases of lock and non-lock

There is a problem that the loss of reference clock does not report the loss of lock, and the narrow pulse of the phase detector cannot be detected.

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