The Research Of Pseudo Random Sweep Signal Design

Seismic exploration is one of the important methods of geophysical exploration.It is now being developed into "Wide azimuth-broadband-High Density" technology.The vibrator can provide the realization with high efficiency and broadband for "Wide azimuth-broadband-High Density" technology.The shoot of seismic is an important part in seismic exploration system.The quality of the shoot signal directly influences the exploration resolution.The vibrator shoots with controllable long duration and low amplitude continuous vibration instead of the instantaneous excitation wave of shock source.The resolution of seismic exploration is determined by the resolution of seismic wavelet,and the resolution of the vibroseis is determined by the resolution of its sweep correlation.The resolution of wavelet is determined by its shape,if the main lobe is prominent,and the side lobe is small,the resolution is high,or the resolution is low.So the autocorrelation of the vibrator sweep is an important factor to affect the exploration resolution,and it is very important to study how to improve the resolution of correlation wavelet.Giving us a application in the vibroseis system.Pseudo random sequences with good autocorrelation properties,and is a kind of periodic signal,cycle length is determined by order of the shift register,bandwidth through the clock frequency changing is achieved,so the correlation wavelet has a narrow peak or a wide power spectrum,so the using of pseudo random sequence is an effective approach to improve the resolution of correlation wavelet.Based on the analysis of the linear sweep and the nonlinear sweep,the paper focuses on the sweep design of the two element m sequence pseudo random sweep,the three element m sequence pseudo random sweep and the pseudo random sweep based on shaping filter,and it is valid using this method in the field.