The Research Of Zoom FFT Technique Based On Low Frequency Electromagnetic Signal

With the continual progress of science and technology and the rapid development of information technology,how to measure the signal spectrum conveniently,rapidly and accurately plays a very important part in the low frequency electromagnetic signal analysis and process. In the analysis of signal spectrum, one of the most commonly used methods is the Fast Fourier Transform,but if it needs to get more sophisticated structural features of the spectrum and improve the frequency resolution,it needs to study the low frequency electromagnetic signal through the Zoom FFT technique.In this paper, the principle of the Complex Modulation Zoom FFT,Chirp-Z Zoom FFT and Phase Compensation Zoom FFT are introduced at first, on the basis of these three methods,it determines the arithmetic of the three Zoom FFT technique,then combined with the Matlab simulation technology to programming,using the Zoom FFT technique to simulate the same simulation low frequency electromagnetic signal through these three arithmetic.Through the comparison of the measured values,computation and the computation time, it gets the characteristic and the range of applications of the Zoom FFT technique in the low frequency electromagnetic signal. Finally, the result is verified by the actual voice signal, the turbine vibration signal and the seismic signal,which achieve a fairly good result, then the study of this paper is finished.The analysis shows that the Complex Modulation Zoom FFT suitable for small multiple,wide frequency band and less transform occasion in the low frequency electromagnetic signal, the Complex Modulation Zoom FFT have very good resolution on the interference phenomenon of the spectrum;The biggest advantages of the Chirp-Z Zoom FFT is to adjust the zoom band and magnification flexibility,the Chirp-Z Zoom FFT can achieve highly accurate zoom purpose when the fence effect cause spectrum aliasing;Phase Compensation Zoom is more suitable for the high frequency band spectrum zoom.In a word,the Zoom FFT technique is effective and feasible in the low frequency electromagnetic signal,which can implement a spectrum analysis of narrowband and improve the frequency resolution, and also the Zoom FFT technique provide a basis for the low frequency electromagnetic signal research.