Patent ID: 9664038
Date: 2017-05-30
CPC Classifications: E21B,G08C,H04J,H04L

Claim:
1. A method for transmitting a data frame of an electromagnetic (EM) telemetry signal to or from a downhole location, the method comprising: (a) transmitting all of a long header at a first frequency, wherein the EM telemetry signal comprises the long header and the data frame; (b) transmitting all of the data frame at a second frequency different from the first frequency, wherein the first frequency and the second frequency are sufficiently separated to permit demodulation of the long header transmitted at the first frequency and the data frame transmitted at the second frequency; and wherein wherein f is one of the first and second frequencies, f′ the other of the first and second frequencies, f>f′, c is cycles per bit transmitted at f, c′ is cycles per bit transmitted at f′, c>1, and c′>1.