| 摘要 |
An electrical signalling system comprises a modulator arranged to accept information and encode that information in an alternating signal containing repeated rising and falling edges, the encoding being by way of the time between consecutive rising and falling edges a transmission path for the signal from the modulator to a demodulator, wherein the modulator is arranged to precede a data signal with a reference signal of a known time, and the demodulator is arranged to detect that reference signal and calculate a calibration error therefrom. The demodulator can record the calibration error and subtract this from subsequent data signals. The demodulator can alternatively (or in addition) adjust the threshold for future signals, on the basis of the calibration error. This is particularly suited to inductive transmission paths such as a three-phase electrical supply cable leading to downhole sensors in the oil and gas extraction industries. |
