Frequency synthesis system for enhancing spectrum purity of direct digital frequency synthesizer

A frequency synthesizer, frequency synthesis technology, applied in the direction of automatic power control, electrical components, etc., can solve the problems of low signal spurious suppression, high cost, etc., and achieve the effect of high-quality signal synthesis

CN101847992AInactive Publication Date: 2010-09-29NANJING GUORUI ANTAIXIN TECH
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Patent Information

Authority / Receiving Office
CN · China
Current Assignee / Owner
Publication Date
2010-09-29
Estimated Expiration
Not applicable · inactive patent

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Abstract

The invention relates to a frequency synthesis system for enhancing spectrum purity of a direct digital frequency synthesizer, which comprises a crystal oscillator, a phase-locked loop module (PLL), a direct digital frequency synthesis module (DDS), a filter module and a central processing unit, wherein the system uses the phase-locked loop module (PLL) to provide a variable clock for the direct digital frequency synthesis module (DDS), and the clock frequency of the variable clock provided by the phase-locked loop module (PLL) is an integral multiple of the frequency of the output signal. By changing the clock frequency of the direct digital frequency synthesizer, the noise generated in the quantization process is minimized, thereby improving the stray indexes of the output signal and enhancing the spectrum purity of the output signal.
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Description

technical field

[0001] The invention relates to a brand-new system for improving the spectrum purity of direct digital frequency synthesizers, especially a frequency synthesis system with extremely wide application prospects in the military, communication and instrument industries, specifically to improve the frequency spectrum of direct digital frequency synthesizers Pure frequency synthesis system. Background technique

[0002] The direct digital frequency synthesizer is one of the most commonly used baseband signal generators in the fields of modern wireless communication, radar and electronic countermeasures, but because it uses an all-digital frequency synthesis method, the noise generated during digital quantization and sampling cannot be completely eliminated. affects its use to a great extent. At present, the direct digital frequency synthesizer produced by ADI is one of the most commonly used direct digital frequency synthesizer DDS chips, but the best spurious sup...

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Embodiment Construction

[0017] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0018] Such as figure 1 Shown, a kind of frequency synthesis system that improves the spectral purity of direct digital frequency synthesizer, it comprises crystal oscillator OSC, phase-locked loop module PLL, direct digital frequency synthesis module DDS, filtering module and central processing unit, described The crystal oscillator OSC provides the system clock for the frequency synthesis system. The signal output terminal of the crystal oscillator OSC is connected to the reference clock signal input terminal of the phase-locked loop module PLL. The variable clock signal output terminal of the phase-locked loop module PLL is connected to the direct digital The variable clock signal input terminal of the frequency synthesis module DDS is connected, the control signal input terminals of the direct digital frequency synthesis module DDS and the phase-loc...