System and method for reducing harmonic noise of digital-synthesis sine waves

Abstract

The invention provides a system and a method for reducing the harmonic noise of digital-synthesis sine waves. The system comprises a frequency and phase controller, a digital-synthesis sine wave circuit, a harmonic counteraction function generation circuit, an adder circuit and a low-pass filter, the harmonic counteraction function generation circuit is utilized to control the digital-synthesis sine wave circuit to generate a step sine wave according to a set frequency, meanwhile, the harmonic counteraction function generation circuit is controlled to generate a 'harmonic counteraction function wave' synchronized with the step sine wave, the two signals are superposed by the adder circuit, the fundamental wave signal and the M-1 harmonic component in an output signal are not counteracted, other harmonic components are remarkably reduced, the output signal then passes through the low-pass filter, a cutoff frequency is appropriately selected, so that M-1 and higher subharmonics far from the fundamental wave can be filtered, and thereby a sine wave signal with little harmonic noise can be obtained.

Description

technical field [0001] The invention relates to the fields of measurement and control, in particular to a system and method for reducing digitally synthesized sine wave harmonic noise. Background technique [0002] As a test or carrier signal, the sine wave has a wide range of applications and is the most important and basic waveform. In practical applications, how to reduce the harmonic noise in the process of sine wave generation is a very basic and important research topic. Digitally synthesized sine wave is a technology that uses a digital-to-analog converter (D / A converter) as the core to generate a sine wave signal by fitting a rectangular step. It has a wide range of applications in the fields of measurement and control. Tests and analysis have shown that generally digitally synthesized sine waves have relatively large harmonic noise. To generate low-noise sine waves, it is generally improved by subsequent high-order low-pass filtering, but when the frequency is requi...

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Problems solved by technology

Tests and analysis have shown that generally digitally synthesized sine waves have relatively large harmonic noise. To generate low-noise sine waves, it is generally improved by subsequent high-order low-pass filtering, but when the frequency is required to be adjustable, the subsequent filter circuit It is very difficult to design and implement, especially when it is necessary to generate high-precision and low-noise digitally synthesized sine waves with adjustable frequency, it is almost impossible to achieve

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