METHOD FOR MEASURING FREQUENCY BY FOURIER ANALYSIS

PURPOSE:To sample and quantize a signal to be measured, multiply it by a window function, determine the complex frequency component in the signal by the Fourier analysis, substitute it to a specified expression together with the corresponding frequency, and precisely determine the frequency and coefficient of damping divergence coefficient of the signal. CONSTITUTION:Various waveforms generated by a waveform generator l are sampled by a sampling and holding circuit 3, and the sampled waveform voltages are quantized by an A/D converter 4. These are read by a personal computer 5, which then multiplies them by a window function to weight the data. The discrete Fourier transform is calculated from the data to determine the amplitude spectra. The arithmetic operation is conducted with complex data, and the amplitude spectra are determined as complex frequency components. The complex frequency components V1--Vn and the corresponding frequencies F1-Fn are substituted to the expression to calculate the frequency Fx and coefficient 2piFy, of damping divergence of the signal to be measured, and the results are outputted to a display device 6 and a printer 7.