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MODEL 3148 LOG-PERIODIC DIPOLE ARRAY ANTENNA
Application
© EMC TEST SYSTEMS, L.P. – SEPTEMBER 2002
5
REV C – PN 399239
APPLICATION
Install the Model 3148 on an ETS-Lindgren tripod or antenna mast
adapter. Connect an N-type coaxial cable from the antenna
connector to a generator (immunity) or receiver (emissions). Both
horizontal and vertical polarization are easily accomplished when
the Model 3148 is mounted on a tower or tripod. Contact with any
metallic or non-metallic structure can capacitively load the antenna
which may cause inconsistent results. Therefore, care must be
taken to ensure that no part of the dipole elements are in contact
with the tripod or tower, particularly in vertically-polarized tests.
Where possible, run the feed cable straight at least 1 meter or more
back from the Model 3148 before dropping vertically.
For emissions measurements, electric field strength in db[V/m] is
obtained from
E(dBV/m)=V(dBV)+AF(dB1/m)+
α
(dB),
Where
V
is the receiver or spectrum analyzer voltage reading,
AF
is antenna factor (see attached calibration data), and
α
is 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
d
pg
m
V
E
30
)
/
(
=
,
where
d
is in meters,
g
is the numeric gain (10
G[dB]/10
, see attached
calibration data), and
P
is antenna net input power in watts. An
estimate of the power required in free space condition for any field
strength
E
can be obtained from the forward power graphs in the
“Typical Data” section, 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).