Device and method for measuring small signal harmonic distortion traced by fundamental waves

A harmonic distortion and small-signal technology, applied in the field of signal measurement, can solve problems such as difficult calibration, notch filter characteristics vary greatly with ambient temperature, and difficult to implement

Inactive Publication Date: 2010-02-03
THE 41ST INST OF CHINA ELECTRONICS TECH GRP
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Problems solved by technology

From the point of view of circuit implementation, it is possible to design a notch filter that attenuates the fundamental wave and produces a small attenuation of the second and above harmonics, but it is difficult to implement and the tunable notch The characteristics of the device change greatly with the ambient temperature, and it is difficult to calibrate

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  • Device and method for measuring small signal harmonic distortion traced by fundamental waves
  • Device and method for measuring small signal harmonic distortion traced by fundamental waves
  • Device and method for measuring small signal harmonic distortion traced by fundamental waves

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Embodiment Construction

[0049]The purpose of the present invention is to transfer the measured signal from the time domain to the frequency domain, and realize the accurate measurement of the harmonic distortion of the measured signal through the spectrum analysis of the signal in the frequency domain. The present invention first accurately measures the frequency of the signal to be measured, then adjusts the sampling frequency of the AD converter, so that the sampling frequency of the AD converter becomes an integer multiple according to the set number of sampling points and the measured fundamental wave frequency, and finally performs an integer multiple of the sample data. FFT (Fast Fourier Transform) transform extracts the fundamental amplitude of the measured signal and the corresponding Nth harmonic amplitude in the frequency domain to calculate the harmonic distortion of the measured signal.

[0050] Preferred embodiments of the present invention will be specifically described below in conjunct...

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Abstract

The invention discloses a device and a method for measuring small signal harmonic distortion traced by fundamental waves, wherein the device comprises an interface unit, an automatic gain unit, a peakvalue detection unit, a low-pass filter unit, a frequency measurement unit, an AD conversion unit, and an FIFO, DDS, FPGA and DSP signal processing unit. The frequency of signals to be measured is accurately measured firstly, then the sampling frequency of an AD converter is regulated to enable the sampling frequency of the AD converter to be in a multiple integer relationship with fundamental wave frequency which is measured according to the set sample point amount, and finally FFT conversion is carried out on sample data and fundamental wave amplitude of the signals to be measured and corresponding amplitude of N harmonic waves are extracted from a frequency domain, thereby calculating the harmonic distortion of the signals to be measured.

Description

technical field [0001] The invention relates to the technical field of signal measurement, in particular to a measurement device and method for small signal harmonic distortion of fundamental wave tracking. Background technique [0002] At present, the most commonly used distortion measurement method is the fundamental wave rejection method, with figure 1 Simplified block diagram for fundamental wave rejection method distortion measurement. The most important functional block is the tunable notch filter. When working, the filter is manually or automatically tuned to the fundamental wave of the sine wave, the fundamental wave is greatly attenuated, and the second and higher harmonics are as low as possible. Attenuation or no attenuation, so that harmonics can pass through basically without attenuation, broadband noise and hum related to AC power, and any other interference signals above and below the frequency of the notch filter can also pass through without attenuation. F...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01R23/16G01R23/20
Inventor 李少东
Owner THE 41ST INST OF CHINA ELECTRONICS TECH GRP
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