Method of and apparatus for the generation and transmission of signals for echolocation and other signalling purposes, such as in geophysical exploration

摘要

Methods and apparatus are described for generating and transmitting signals in accordance with a sequence which defines the time relationship of the signals. Each signal has a band width covering several octaves and may be a pulse. During a transmission interval the repetition frequencies of the signals monotonically sweep in a coherent relationship over bands restricted to an octave such that the spectrum of the sequence has substantially constant energy over a frequency range much larger than an octave. The autocorrelation function of the sequence is characterized by an absence of side lobes which would indicate false targets or produce a high noise level upon processing of the signals in an echolocation system, such as a geophysical exploration system in which the seismograms are constructed by cross correlation of the signals which are received from the geological reflection surfaces with a stored replica of the transmitted signals. The signals can be generated by a plurality of sources all of which operate during the transmission interval, thus enabling the transmission of increased energy into the medium (viz., the seismic signal power injected into the earth).