Transient Constant Area Surface and Downhole Wave Models - Measurement While Drilling Signal Analysis, Optimization and Design - page 138

The previous simulation is repeated assuming a 24 Hz carrier wave. The
time delay between pulser and drillbit is 0.01 sec. As seen from Figure 4.6e, the
(blue) recovery of the black signal from the green data is very good.
C CASE 4. PHASE-SHIFTING (F = FREQUENCY IN HERTZ)
PI = 3.14159
A = 0.25
F = 24.
PERIOD = 1./F
IF(T.GE.0.0. AND.T.LE. PERIOD) SIGNAL = +A*SIN(2.*PI*F*T)
IF(T.GE.PERIOD.AND.T.LE.2.*PERIOD) SIGNAL = -A*SIN(2.*PI*F*T)
IF(T. GE.2.*PERIOD) SIGNAL = 0.
4.6.8 Run 5. Phase-shift-keying, 48 Hz carrier.
Finally, we repeat the above run assuming a 48 Hz carrier wave. The time
delay between pulser and bit is 0.01 sec. As shown in Figure 4.6f, the green
pressure traveling up the drillpipe does not at all resemble the intended black
signal. However, the blue curve, obtained using only green data alone,
successfully replicates the black curve. Recovery is excellent.
C CASE 5. PHASE-SHIFTING (F = FREQUENCY IN HERTZ)
PI = 3.14159
A = 0.7
F = 48.
PERIOD = 1./F
IF(T.GE.0.0. AND.T.LE. PERIOD) SIGNAL = +A*SIN(2.*PI*F*T)
IF(T.GE.PERIOD.AND.T.LE.2.*PERIOD) SIGNAL = -A*SIN(2.*PI*F*T)
IF(T. GE.2.*PERIOD) SIGNAL = 0.
C
Figure 4.6f. Phase-shift-keying, 48 Hz carrier wave.