TRANSMISSION OF WELL-LOGGING DATA OVER BANDPASS CHANNELS USING QUADRATURE AMPLITUDE MODULATION

摘要

A method and apparatus for transmitting and receiving acquired digital dataover bandpass channels (i.e. channels havinga limited range of frequencies) at high data transmission rates. Combinedamplitude and phase modulation (quadrature ampli-tude modulation) is applied to the digital data and the sampled digitalwaveform converted to an analog waveform for passageover the bandpass channel. The sample rate is chosen as an integer multiple ofthe symbol rate and carrier frequency to signifi-cantly reduce processing overhead. Reception of the acquired data is similarto transmission and involves an analogous ampli-tude and phase demodulation. The quadrature amplitude modulation technique ofthe present invention is applied to an oil well-logging application to transmit the data acquired from the downhole logginginstruments over the logging cable (bandpasschannel) at high transmission rates.