A circuit and method for fast locking of a phase-locked loop

Abstract

The invention provides a phase-locking loop rapid locking circuit and method. The phase-locking loop rapid locking circuit is provided with two loops of a broadband wide loop filter and a narrowband wide loop filter. At the beginning, the broadband wide loop filter is used as a loop filter in a phase-locking loop; the controlled voltage presetting is simultaneously carried out on the broadband wide loop filter and the narrowband wide loop filter so that a frequency difference in a phase discriminator in the phase-locking loop is rapidly reduced to a smaller value; and the smaller the frequency difference is in the process, the shorter the time used in the capturing phase T1 is. After the voltage presetting of the broadband wide loop filter is stable, the broadband wide loop filter carries out voltage presetting on the narrowband wide loop filter, and thereby, the narrowband wide loop filter obtains accurate preset controlled voltage, and the narrowband wide loop filter is used as a loop fiber in the phase-locking loop. The narrowband wide loop filter used by the phase-locking loop in the final stable phase adopts a narrowband wide loop, therefore, the phase noise of the phase-locking loop can not be deteriorated.

Description

technical field [0001] The invention relates to the technical field of wireless communication, in particular to a circuit and method for fast locking of a phase-locked loop. Background technique [0002] At present, the digital mobile radio (DMR, DigitalMobileRadio) communication interphone adopts the time division multiple access (TDMA, TimeDivisionMultipleAccess) technology, but due to the technical limitation of the locking time, it can only realize half-duplex communication at present. If the locking time of the phase-locked loop can be controlled within 1ms, the walkie-talkie is expected to realize full-duplex communication and frequency-hopping communication in TDMA mode. [0003] A phase-locked loop (PLL, Phase-Locked Loop) can automatically track the frequency of the output signal to the frequency of the input signal. During the working process of the phase-locked loop, when the frequency of the output signal is equal to the frequency of the input signal, the output...

AI Technical Summary

Problems solved by technology

Increased loop bandwidth can improve lock speed, but at the same time phase noise will increase

On the contrary, the reduction of the loop bandwidth can reduce the phase noise, but it will prolong the locking time

[0017] The time required for the oscillation frequency of the voltage-controlled oscillator in the phase-locked loop to switch between two frequency points is related to the frequency interval between the two frequency points. The larger the two frequency intervals, the larger the corresponding voltage control voltage difference , so the longer switching time required

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