Transient Constant Area Surface and Downhole Wave Models - Measurement While Drilling Signal Analysis, Optimization and Design - page 137

4.6.6 Run 3. Phase-shift-keying, 12 Hz carrier wave.
Here we consider a phase-shift keying example. The time delay between
pulser and drillbit is 0.01 sec. In Figure 4.6d, the black bottom curve is the
intended signal, while the green curve combines the downward wave reflected at
the open-end bit. The black and green traces appear similar, at least
qualitatively, but the green is wider. The sharp phase shift in the black appears
as a stretched-out wave in the green. Recovery is very good.
C CASE 3. PHASE-SHIFTING (F = FREQUENCY IN HERTZ)
PI = 3.14159
A = 0.25
F = 12.
C G = A*SIN(2.*PI*F*T)
C Means 2*PI*F cycles in 2*PI secs, or F cycles per sec, F is Hz.
C One cycle requires time PERIOD = 1./F
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.

Figure 4.6d . Phase-shift-keying, 12 Hz carrier (blue and black are identical).

4.6.7 Run 4. Phase-shift-keying, 24 Hz carrier wave.

Figure 4.6e. Phase-shift-keying, 24 Hz carrier wave.