Multi-mode frequency-dividing apparatus and method for expanding frequency-dividing range of multi-mode frequency divider

Abstract

The invention provides a multimode frequency dividing device for expanding the frequency dividing range of a multimode frequency divider in a fraction phase-locked loop. The device comprises a multimode frequency divider (302) and a circuit module (304) which is used for expanding the frequency dividing range. The circuit module comprises a first selection control signal generator (3042) which isused for comparing a n stage output signal with a (n-1) stage output signal of the multimode frequency divider and generating a first selection control signal according to the comparison result and afrequency dividing ratio control signal, a first selector (3044) which is used for selecting and outputting the n stage output signal of the multimode frequency divider or an inversion signal of the n stage output signal according to the first selection control signal, a second selection control signal generator (3046) which is used for generating a second selection control signal according to the (n-1) stage output signal of the multimode frequency divider and the frequency dividing ratio control signal as well as a second selector (3048) which is used for selecting and outputting the (n-1) stage output signal of the multimode frequency divider or the signal output by the first selector according to the second selection control signal.

Description

technical field [0001] The present invention relates to a fractional phase-locked loop, in particular to a multi-mode frequency division device for expanding the frequency division range of a multi-mode frequency divider in a fractional phase-locked loop and a method for extending the frequency division range of the multi-mode frequency division device . Background technique [0002] According to the type of loop frequency divider, the phase locked loop can be divided into two categories: integer frequency division phase locked loop and fractional frequency division phase locked loop. Compared with the integer frequency division PLL, the fractional frequency division PLL has the advantages of fast locking speed, high frequency synthesis accuracy and higher reference frequency, so it has been more and more widely used in communication transceivers . [0003] The traditional fractional frequency division phase-locked loop such as figure 1 As shown, including: multi-mode fre...

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Problems solved by technology

[0009] The present invention aims to provide a method for solving the problem of the frequency division ratio error of the first period after switching caused by the uncertainty of the level state after switching between the (n-1) level and the nth level of the multi-mode frequency divider. Multi-mode frequency division device and method

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