ETS-Lindgren 3149 Hybrid Log Periodic and Bowtie (BiConiLog) - Manual (Page 25)

Application | 25
6.0 Application
For emissions measurements, electric field strength in db[V/m] is obtained from:
E(dB[V/m])=V(dB[V])+AF(dB[1/m])+ α(dB)
V = the receiver or spectrum analyzer voltage reading
AF = antenna factor
α
= cable loss in dB, if cable losses are non-negligible
For immunity testing, the electric field strength generated at a distance d can be
approximated by:
( )
E
Pg
d
V / m
=
30
d = distance, in meters
g = numeric gain (10
G[dB]/10
)
P = antenna net input power, in watts
An estimate of the power required for any field strength E can be obtained from
the gain or forward power graphs in Typical Data on page 27, which shows
power required in watts to generate 1 V/m. For any other field strength not
shown, multiply the power in watts by the desired E-field squared, or:
P(E V/m) = E 2 P(1 V/m)
Actual transmitted field strength should be verified using an ETS-Lindgren
electric field probe, or equivalent.
For IEC 1000-4-3 type testing, the antenna tip can be placed at any distance
between one and three meters from the EUT as long as the front face plane is
illuminated according to the -0, +6 dB uniform field specification. In general,
closer distances require less power to create a given field strength