| 摘要 |
Quasi-periodic pulse trains are generated and swept in repetition frequency over an octave. Spectral harmonics of the pulse trains which prevent the trains from having a "flat" power spectrum over a frequency range much greater than an octave are reduced or eliminated by adjusting the shape of the pulses in the trains. By selecting the timing of the pulses, other harmonics are reduced or preferentially augmented. The spectral energy of the signals which are generated during a transmission onterval is of the type which possesses an autocorrelation function with a narrow main lobe and low side lobe levels which is especially suitable for echo location purposes such as in geophysical exploration in which seismograms are constructed by cross correlation of the signals which are transmitted with those which are received from geological reflection surfaces. |
