Loop Antenna
Active
50 50 Q Transmitter Fiber-optic Cable
PIC
Controller
Battery
12 V 50 Q In-line Terminator
Metal Enclosure
Figure 3-31. Diagram of a 2002 MSE magnetic field measurement.
the voltage present at the input of the fiber-optic transmitter modified by the fiber-optic
link. If the effect of the link is assumed to be a frequency independent gain or
attenuation (of value Glink), then the expression for the voltage at the input of the
oscilloscope, vcope(t), is
1 RFOT
Vscope(t) = AloopkintGcGlnk RF Bnorm(t) (3-124)
2 G ik \Rout + RFOT )
For the 2001 experiment, Aloop = 0.533 m2, Gpjc = 1, kit = 1.96 x 104 s-1, and
Glink will be assumed to have a nominal value of one. The quantity RFOT is 68 kQ, the
input resistance of the Opticomm MMV-120C fiber-optic transmitter, and Rout is 50 Q.
Therefore, the quantity RFOT/(Rout +RFOT) is approximately unity. The expression for
the nominal voltage seen at the input of the digitizer during the 2001 experiment, when
Bnorm(t) is expressed in units of Wb m 2, is given by
Vscope-nom(t) = (5220)Bnorm(t)
(3-125)