Typically the source impedance is considered a resistance, Rloop, in series with an
inductive reactance, j0Lloop. Therefore, the source impedance is
ZS = Rloop + jLloop (3-81)
The load impedance is considered a resistance, Rload, and hence
ZL = Rload (3-82)
Substituting the expressions for the source and load impedances (Equations 3-81
and 3-82) into the expression for the frequency-domain output voltage of the loop
antenna (Equation 3-80) yields
Vot, (C) = ( A-oJ-Rloadload joBnorm (CO) (3-83)
jcoLloop +Rloop +Rload /
As with the flat-plate antenna, the response of the loop antenna in the frequency
domain depends on whether the antenna is to be viewed as a magnetic field sensor
or a magnetic field time-derivative sensor. Unlike the flat-plate antenna, only the
time-derivative perspective will be considered for the loop antenna, since active
integration will be used to extend the loop antenna into a magnetic field sensor. From
the dB/dt antenna perspective, the magnitude response of the antenna, GdB (C), is given
dt
by
Gd (o) Vout (co) _AloopRload (3-84)
GjdB (C) = (3-84)
dt jBBnorm (C) jLloop + Rloop + Rload
Like the dE/dt antenna, the magnitude response of the dB/dt antenna is that of a
first order low-pass filter. The magnitude response is given by
GdB(o)= AlolpRoad--1 (3-85)
t Roop +Rload + Lp 2
SAlpRldloop load
Gt ( )RI +Rod [ i1O'~l~ ] ~ (-