Patent ID: 8098070

Claim:
A low noise high sensitivity instrument for sensing details of a subterranean space, the instrument comprising in combination: at least one transmitter; said transmitter including at least one transmitter coil antenna adapted to emit a transmitter electromagnetic signal; at least one receiver; said receiver including at least one receiver coil antenna; said receiver coil antenna adapted to receive an electromagnetic receiver signal responsive to said transmitter electromagnetic signal; said at least one receiver coil antenna having two wire winding segments divided by a central plane perpendicular to a central axis of said receiver coil, said two wire segments wrapped in opposite directions and coupled together across said central plane with ends of said wire winding segments opposite said central plane defining opposite leads of said receiver coil antenna, said opposite leads sensed by said receiver to measure a difference in signals sensed by said opposite leads; wherein said opposite leads are coupled to differential inputs of a differential amplifier, said differential amplifier adapted to amplify a difference between said opposite leads; and wherein a circuit including said differential amplifier therein includes a reference voltage coupled to both said differential amplifier and to a portion of said receiver coil between said two wire winding segments, such that a reference voltage for said amplifier corresponds with a voltage at a midpoint of said coil between said two wire winding segments.