Transient Constant Area Surface and Downhole Wave Models - Measurement While Drilling Signal Analysis, Optimization and Design - page 108

In Figure 4.li, the green signal is 50% wider than the black signal and is showing
severe distortion compared to the original black signal. However, our algorithm
using the blue data recovers the black curve successfully.
Finally, we ambitiously increase our carrier wave frequency to 96 Hz in
order to test the robustness of our scheme. The following parameters are used.
x Roundtrip delay = 0.02 sec
x Sampling time = 0.0002 sec
This very, very high data rate run with narrow black pulse shows how the
incident and reflected red wave can superpose in the green signal to appear as a
longer duration signal with additional fictitious phase shifts. This effect is
detrimental to high-data-rate continuous wave telemetry. However, using the
green data only, the blue curve recovers the black curve very nicely. Results are
shown in Figure 4.1j.
Figure 4.1j . Very, very high 96 Hz carrier with PSK.
4.2 Method 4-2. Upgoing wave reflection at solid boundary,
single transducer deconvolution using delay equation, with
mud pump noise (software reference, HYBRID*.FOR).
4.2.1 Physical problem.
This single transducer approach is similar to Method 4-1, except that the
mudpump noise measured at the pump is delayed and subtracted from the
standpipe transducer signal (which now records both upgoing and reflected
signals, plus mudpump noise). Once the pump noise is subtracted, the algorithm
is identical to Method 4-1. This capability is listed as a separate method only
because of subtle differences in software structure. As in Method 4-1, this
method does not handle wave shape distortion induced by the desurger.