Fractional N frequency division circuit and method applied to frequency synthesizer

A frequency synthesizer, frequency division circuit technology, applied in the direction of automatic power control, electrical components, etc., can solve the problems of poor anti-noise ability, glitches, and deterioration of the overall phase noise of the frequency synthesizer, so as to achieve smooth spectrum and reduce glitches Effect
CN110190847AActive Publication Date: 2019-08-30XIAN UNIV OF POSTS & TELECOMM
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
XIAN UNIV OF POSTS & TELECOMM
Publication Date
2019-08-30

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Abstract

In order to solve the structure parasitic problem of a fractional frequency division circuit of a Sigma-delta modulator adopting a MASH1-1-1 structure, the invention provides a fractional N frequencydivision circuit and method applied to a frequency synthesizer. The fractional N frequency division circuit comprises a MASH1-1-1 Sigma-delta modulator, a frequency division counting circuit Ncount, afront P / (P + 1) prescaler, a pseudo-random sequence generation circuit Ditcher and an adder; the pseudorandom sequence generation circuit Ditcher is used for generating an n-bit pseudorandom sequenceand sending the n-bit pseudorandom sequence into the n-bit adder I; and the n-bit adder I is used for summing the small numerical value N _ frac [n-1: 0] received by the fractional N frequency division circuit and the n-bit pseudorandom sequence in each clock period, and sending a summing result corresponding to each clock period to the input end of the MASH1-1-1 Sigma-delta modulator.
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Description

technical field

[0001] The invention belongs to the technical field of frequency synthesizers, and relates to a fractional-N frequency division circuit and method applied to frequency synthesizers. Background technique

[0002] When the RF chip is doing signal processing, the RF chip needs to filter, amplify, and down-convert the received signal, and then perform A / D conversion on the analog signal obtained by the down-conversion, thereby generating a digital signal that can be processed by the baseband circuit. The local oscillator frequency for down-conversion is generated by a frequency synthesizer after multiplying the reference frequency generated by a crystal oscillator, and in the frequency synthesizer, the frequency divider is the key to providing multiple high-precision frequency signals. The frequency divider in the traditional frequency synthesizer is an integer frequency division structure. In order to generate adjacent channel frequencies with small frequency in...

Claims

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