A phase-locked loop capable of fast locking and its locking method

Abstract

The invention discloses a fast-lockable phase-locked loop and a locking method thereof. The fast-lockable phase-locked loop includes a filter control unit and a loop filter with adjustable bandwidth. The voltage-controlled oscillator passes The loop filter is connected to the digital phase frequency detector, the filter control unit is connected to the loop filter, and the filter control unit is used to change the circuit of the loop filter when the phase-locked loop is working To widen the loop bandwidth to increase the locking speed of the phase-locked loop, and restore the circuit of the loop filter to restore the loop bandwidth after the phase-locked loop is locked. The invention widens the loop bandwidth by changing the circuit of the loop filter, thereby further improving the locking speed of the phase-locked loop, reducing the locking time of the phase-locked loop, and the cost is low.

Description

Technical field [0001] The present invention relates to a phase locked loop locked technology, and particularly relates to a rapid locking method and lock the PLL. Background technique [0002] Process, the phase difference caused by the phase detector periodically varying phase change due to frequency lock control voltage fall due to a conventional PLL lock, delaying the entire locking process, causing the locking time is too slow in many communication applications can not meet the need. [0003] Currently there are some ways to increase the speed of the PLL is locked, and even patents, the general idea is to charge to the loop filter by using flash to improve the slow process of climbing loop frequency control voltage change causes a waste of time, this thinking no doubt to bring a faster PLL lock speed and improve the performance of the PLL is locked, but this way the circuit is more complex, but also to bring additional power circuit, the higher the cost. [0004] Thus the pr...

AI Technical Summary

Problems solved by technology

[0002] In the conventional PLL locking process, due to the change of the locking frequency, the control voltage drops due to the periodic change of the phase difference of the phase detector, which delays the entire locking process, resulting in too slow locking time that cannot meet many communication applications. need

[0003] At present, there are some methods to improve the locking speed of PLL, and there are even related patents. The general idea is to improve the time wasted in the slow ramp-up process of the loop control voltage caused by frequency changes by charging the loop filter quickly. This The idea undoubtedly brings faster locking speed to the PLL and improves the locking performance of the PLL, but the circuit in this way is more complicated, and it brings additional power consumption to the circuit, and the cost is high

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