Signal frequency measurement method based on three DFT complex spectral lines
A technology of signal frequency and measurement method, applied in the direction of spectrum analysis/Fourier analysis, etc., can solve the problems of low measurement accuracy, large amount of calculation, and ineffective suppression of signal sidelobe interference at other frequency points
Inactive Publication Date: 2016-03-02
常州昊云工控科技有限公司
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[0006] The disadvantage of existing methods is that the highest spectral line search is based on the spectral line amplitude
Moreover, obtaining the spectral line amplitude requires calculating the sum of the squares of the real and imaginary parts, and then taking the square root, which is a large amount of calculation
Existing methods for intermediate parameters gamma The calculation is also based on the amplitude of the spectral line. At the same time, although multiple spectral lines are used, the sidelobe interference of signals at other frequency points is not effectively suppressed, and the measurement accuracy is low.
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[0049] 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:
[0050] 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:
[0051] ,
[0052] in w ( n )choose N = Hanning window function sequence of 512 points, namely:
[0053] , n =0:( N -1);
[0054] 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);
[0055] Step (3): In the range of discrete frequency numbers [15,23], that is, within the range of corresponding frequencies [43.945,67.383...
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The invention relates to a signal frequency measurement method based on three DFT complex spectral lines, belonging to the field of signal parameter measurement technology. The method is characterized in that the processing procedure comprises that: a sampling signal is subjected to windowing processing and then is subjected to DFT transform, a highest spectral line and a second highest spectral line are searched through comparing spectral line amplitude values or the sum of real and imaginary part absolute values in a corresponding frequency search range, based on the operation of the sum of real and imaginary part absolute values of three spectral lines, offset parameters are obtained through a solution equation, or an inverse function formula or an approximation polynomial, and finally the signal frequency is measured. According to the method, multiplication and square root calculation are avoided in searching the highest spectral line and the second highest spectral line and calculating a middle parameter lambda, so that the signal frequency measurement algorithm realization is simplified. Meanwhile, through figuring out the difference between adjacent spectral lines, the sidelobe interference of other signals is inhibited, and the measurement precision is increased.
Description
technical field [0001] The invention relates to a signal frequency measurement method based on three DFT complex spectral lines, belonging 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 actual signal frequency. In the article "Power Harmonic Analysis Algorithm Based on Three-spectral Interpolation FFT" published in "Proceedings of the Chinese Society for Electrical Engineering" Volume 32, Issue 16 in 2012, it is proposed that after adding windowed Fourier transform to the input discrete signal, by using the highest amplitude Spectral line and its adjacent spectral lines on both sides, the method of interpolating th...
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IPC IPC(8): G01R23/16
Inventor 庞浩
Owner 常州昊云工控科技有限公司