| abstract |
In a well logging tool forming a data stream for telemetry to the surface, an encoding system is located downhole cooperative with surface located decoding equipment. The encoder converts serial data into NRZ symbols, then duobinary code of seven levels and then into quadrature modulating signals on a complex carrier. The decoder at the well surface receives the quadrature modulated complex carrier, forms inphase and quadrature components and decodes the two components. The decoder includes circuit means removing the intersignal distortion and also intersymbol smearing. This enables very significant telemetry ratio. |