| 摘要 |
An apparatus and method of communication through a fluid in a borehole between a first location and a second location are provided. The method comprises producing a first signal at the first location and a second signal at the second location, the first signal and the second signal traveling in opposite directions between a first position and a second position in the borehole, measuring a third signal at the first position indicative of the first and second signals, measuring a fourth signal at the second position indicative of the first and second signals, and using a result of filtering the third signal by a first filter with a result of filtering the fourth signal by a second filter and a third filter for estimating a value of the first signal at at least one frequency at a first output, wherein the first filter, the second filter and the third filter are selected based upon a result at a second output of applying the first filter and the third filter to the third signal and applying the second filter to the fourth signal, and wherein the third filter has a phase shift substantially equal to .pi..
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