| 摘要 |
<p>A submersible electromagnetic (EM) field generator (5) for seafloor electromagnetic surveying comprising an AC to DC converter (18) operable to generate a DC output from an AC input and a switching module (19) operable to generate a waveform driving signal by selectively switching the DC output. The EM field generator also comprises an antenna (20) that is operable to generate an EM field in response to the waveform driving signal. Transient suppression circuits (84, 86, 88, 90, 92) are connected in parallel across DC outputs, each providing suppression tuned to a particular frequency or frequency range. The switches are thus protected against induced back EMF generated when the switches are operated.</p> |
