Measuring while drilling employing cascaded transmission systems

Claim 1

A logging while drilling assembly for use in a borehole and a drilling string and mud in a circulation system comprising: a) a first signal generator means comprising apparatus for generating a signal representative of a sensed downhole condition and mounted downhole near the drill bit of said drilling string; b) a second signal generator means comprising a pulser for generating pressure pulses in said mud and mounted uphole from said first signal generator means, said pulser comprising a valve located between an inside of said drilling string and an outside of said drilling string, said pulser further comprising means for generating said pressure pulses in said mud by opening and closing said valve; e) a first transmission system having its downhole end connected to said first signal generator means and its uphole end connected to said pulser; d) a second transmission system having its downhole end connected to said pulser and its uphole end connected to a pressure transducer at the surface of the earth; e) a receiver of said pressure pulses at the surface for producing an indication of said sensed downhole condition.