| 摘要 |
<p>PURPOSE:To enable the filtering of desired frequency components of a reflected sonic signal in a fixed band width with the passage of time. CONSTITUTION:An air gun 1 transmits a sound wave to the sea bottom according to a drive pulse from a drive pulse source 2. A hydrophone 3 converts the reflected sound wave from the sea bottom into an electric signal to output a reflected sound wave signal S1. A TVG amplifier 4 amplifies the reflected sound wave signal increasing a gain with the passage of time. A filter circuit 5 extracts desired frequency components with the passage of time. Here, a sweep signal generating section 51 of the filter circuit 5 generates a sweep signal Ss with frequency varying with time. A mixing compression part 52 mixes the sweep signal Ss with the reflected sound wave signal S1 amplified with the TVG amplifier 4 to compress a frequency. A narrow band filter 53 is a filter with a fixed passing band to filter an output signal of a mixing compression part 52.</p> |
