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Signal amplitude and phase measurement method based on three DFT plural spectral lines

A technology for phase measurement and signal amplitude, applied to the phase angle between voltage and current, measuring devices, measuring electrical variables, etc., can solve problems such as sidelobe interference and large amount of calculation

Active Publication Date: 2016-03-02
常州昊云工控科技有限公司
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Problems solved by technology

[0009] The disadvantage of the existing method is that the calculation of the signal amplitude and phase is independent of each other. The calculation of the amplitude needs to calculate the sum of the squares of the real part and the imaginary part, and then take the square root, and the calculation of the phase needs to calculate and The angle of two complex numbers, so the amount of calculation is large
At the same time, existing methods are also susceptible to sidelobe interference from other frequency signals

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  • Signal amplitude and phase measurement method based on three DFT plural spectral lines
  • Signal amplitude and phase measurement method based on three DFT plural spectral lines

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Embodiment Construction

[0045] Attached below figure 1 The calculation flow chart shown further illustrates two specific implementations of the present invention. These two embodiments are applied to the measurement of frequency signals around 50 Hz. The first specific embodiment adopts the Hanning window, and its specific steps are as follows:

[0046] Step (1): Set the sampling rate Fs =1500Hz, continuous intercept N = Signal of 512 points x ( n ), perform windowing processing to obtain the windowed signal y ( n ), the windowing formula is:

[0047] ,

[0048] in w ( n )choose N = Hanning window function sequence of 512 points, namely:

[0049] , n =0:( N -1);

[0050] Step (2): Windowed signal y ( n ) to perform discrete Fourier DFT transform to obtain the discrete spectrum Y ( k ), where the discrete frequency number k =0:( N -1);

[0051] Step (3): Depending on the frequency of the signal whose magnitude and phase you want to measure f 0 The corresponding discrete f...

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Abstract

The invention relates to a signal amplitude and phase measurement method based on three DFT plural spectral lines and belongs to the signal parameter measurement technology field. The method is characterized by comprising the steps of carrying out the windowing treatment on a sampling signal and then carrying out the DFI conversion; searching three nearby plural spectral lines corresponding to the frequency of a signal to be measured; based on the plural value of the three spectral lines, through a directly derived formula or an approximate polynomial formula, calculating an intermediate parameter, wherein a final amplitude measurement result is equal to a mould of the intermediate parameter and a final phase measurement result is equal to the sum of the argument of the intermediate parameter and one half of Pi. By adopting the method in the invention, the calculation is performed directly based on a spectral-line complex number. Meanwhile, the mould of each spectral line is not needed, so that the calculated quantity is reduced. Moreover, the calculation process can offset the sidelobe interference of another frequency signal, so that the measurement precision is increased.

Description

technical field [0001] The invention relates to a signal amplitude and phase measurement method based on three DFT complex spectral lines, and belongs to the technical field of signal parameter measurement. Background technique [0002] At present, the method of analyzing frequency signals based on discrete Fourier transform DFT or its fast algorithm FFT has been widely used. However, DFT has a barrier effect, that is, the actual signal frequency may not fall on the discrete spectral line, so it is necessary to use an interpolation algorithm to estimate the frequency, amplitude and phase of the actual signal. In the article "Improved Algorithm for Harmonic Analysis of Power System Using FFT" published in "Journal of China Electrical Engineering Society" Volume 23, Issue 6 in 2003, it is proposed that after adding windowed Fourier transform to the input discrete signal, by selecting the highest amplitude and A method of interpolating the next two spectral lines to measure si...

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Application Information

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IPC IPC(8): G01R23/16G01R25/00
Inventor 庞浩
Owner 常州昊云工控科技有限公司
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