Geology Reference
In-Depth Information
A sampling time of 0.001 sec is used in Figure 4.1g. The green curve does not
look like the black. The blue curve is recovered from the green data, and is
almost identical to the original black curve. The recovery is very successful.
C CASE 3. PHASE-SHIFTING (F = FREQUENCY IN HERTZ)
PI = 3.14159
A = 0.25
F = 24.
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) G = +A*SIN(2.*PI*F*T)
IF(T.GE.PERIOD.AND.T.LE.2.*PERIOD) G = -A*SIN(2.*PI*F*T)
IF(T. GE.2.*PERIOD) G = 0.
Figure 4.1g
. 24 Hz low frequency carrier wave with phase shift keying.
Next we continue with 24 Hz, but instead use finer time sampling, in
particular, selecting
x Roundtrip delay = 0.02 sec
x Sampling time = 0.0005 sec
In Figure 4.1h, the sampling time of 0.0005 sec is used. Both Figures 4.1g and
4.1h show that the green superposed signal is distorted relative to the original
black one. There are two positive crests in the signal, as there are in the original
black signal, and a single bump on the bottom. Also, the green signal is wider
than the black. Intersymbol interference is strong. Also observe how well the
algorithm using the blue signal recovers the black. Next, in Runs 4 and 5, let us
examine very high data rates.
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