Method and apparatus employing phase cycling for reducing crosstalk in downhole tools

A downhole logging tool, comprising:

• a substantially cylindrical tool body;
• a transmitter disposed on the tool body;
• a receiver disposed on the tool body, and wherein the receiver creates a received signal;
• a processor coupled to the transmitter, and also coupled to the receiver;
• a phase-reversal circuit coupled between the receiver and the processor, and wherein the phase reversal circuit is adapted to selectively change a phase of the received signal to create a phase reversed received signal;
• and
• wherein the processor is adapted to compare the received signal to the phase reversed received signal to determine an amount of noise induced in the received signal after its reception.

A method comprising:

• transmitting from a transmitter on a downhole logging tool an electromagnetic signal into an earth formation;
• receiving at a receiver on the downhole tool the electromagnetic signal in a first period to create a first received signal;
• receiving at the receiver on the downhole tool the electromagnetic signal in a second period;
• phase delaying the electromagnetic signal received in the second period to create a second received signal;
• and
• determining, using the first and second received signals, noise induced in a receive circuit of the downhole tool.

An electrical circuit for processing formation data in downhole logging tools, comprising:

• a digital signal processor (DSP);
• a transmission path coupled to said DSP;
• and
• a receive path coupled to said DSP comprising a phase-reversal element;
• wherein the phase-reversal element is used to eliminate electromagnetic interference in the received signal.