Therefore, inserting the expression for Ztota into the Equation 3-10 yields
Vot (o) = jAoFoAplateEnorm(mC) (1 + R ( +c) (3-14)
j1 + jR (Cant + C int)
The interpretation of the response of the antenna in the frequency domain
depends on whether the antenna is to be viewed as an electric field or an electric
field time-derivative sensor. From the dE/dt antenna perspective, the response of the
antenna, Gd (co), is given by
dt
Gd (coo) LO oAplate (3-15)
dt jcoEnorm(c) 1 + jR (Cant + Cint) (3-15)
Typically no integrating capacitor is used with a dE/dt antenna (Cint = 0),
therefore the expression for GdEC (c) reduces to
dt
Gd (CO) = oAplateR (1(RC,,) (3-16)
dt I + jCRCant
This is the response of a first order low-pass filter with magnitude response given
by
Gd (O) =o0ApiateR (3-17)
dt r ^-] 2
II + (RCant\)2
The pass-band gain is equal to coApiateR. The -3 dB point (the frequency at which
the output is approximately 0.707 times the output in the pass-band) of the response is
1
C0o0 = (3-18)
RCant
For example, if R = 50 Q and Cant = 30 pF, then oo = 6.67 x 108 s-1. The
corresponding frequency is
noo 6.67 x 108 s 1
fo -- 106 MHz (3-19)
27 27
Therefore, this example flat-plate dE/dt antenna has a -3 dB bandwidth of
approximately 106 MHz. This flat-plate design is a suitable dE/dt antenna for most