ETS-Lindgren 3140B Hybrid Log Periodic and Bowtie (BiConiLog) - Manual (Page 7)

1.0 Introduction
The ETS-Lindgren
Model 3140B BiConiLog TM is a
high-field antenna in the
bow tie/log periodic family,
providing the highest
field-to-power ratio at low
frequencies of any of the
BiConiLog antennas. The
Model 3140B is designed
specifically to generate the field
levels required for
immunity/susceptibility tests
required by standards such as
IEC/EN 61000-4-3 using the
lowest amount of input power
possible.
A BiConiLog antenna combines a broadband biconical-like bow tie antenna with
a standard log periodic dipole array (LPDA) to replace the traditional use of two
antennas in the 26 MHz to 3000 MHz electromagnetic compatibility (EMC) test
frequency range. Many EMC antennas are variations of a standard tuned dipole,
which must be nearly half a wavelength long to transmit or receive energy most
efficiently; at 26 MHz, a tuned dipole would have to be approximately 5.3 meters
long, 4.6 meters long at 30 MHz, and 2.8 meters long at 50 MHz. This is
unwieldy for many anechoic chambers and test sites. The end plates of the
Model 3140B T bow ties make the bow tie antenna segment look like an antenna
twice as long as the actual 1.6 meter length. The result is about a 10 dB
improvement in low frequency transmit gain compared to a regular bow tie of the
same length.
Although bow ties have been used for all of the elements on some log periodic
antenna designs in the past, in EMC applications the advantage gained is an
extension of the useful low frequency range of the typical LPDA from 100 MHz
down to 26 MHz. At 26 MHz, an efficient single dipole type antenna must be over
five meters long, whereas suitable performance is obtained here with a 1.6 meter
bow tie. A simple wire outline bow tie antenna is narrowband compared to a
sheet bow tie or biconical, so struts are added to the Model 3140B bow ties to
better simulate the broadband sheet bow tie.
Introduction | 7