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

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.

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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Problems solved by technology

[0003] The purpose of the present invention is to solve the problem that the existing frequency synthesis system cannot improve its performance from its own design, the output signal spurious suppression degree after frequency expansion is low, and the cost is high, and proposes a method that can improve direct digital frequency synthesis. The frequency purity of the output signal of the direct digital frequency synthesizer can realize high-quality signal synthesis without increasing the sampling frequency. A frequency synthesis system that improves the spectral purity of the direct digital frequency synthesizer

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