Antenna Frequency Registration

0081-EX-PL-2002 Text Documents

Southwest Research Institute

2002-04-22ELS_55490

In this case, the power output is the "pulsed power" delivered by the pulse generator to the antenna
structure and represents a maximum value for the transmitter. The maximum voltage delivered to the
antenna terminals by the pulse generator is 10 kV. Assuming a terminal impedance of 50 ohms, this
gives a maximum peak power to the antenna terminals of:

Pa =
(10 ⋅10 ) 3 2
= 2 MW
50
The radiation efficiency of the unit is expected to be low since the matching between the source and
antenna has not been fine-tuned as the transmitter is in its early stages of development. The transmitter
vendor quotes a maximum ("worst case") peak electric field value of 1kV/m on boresight at a range of
10 meters. The radiated power, then, can be calculated as:

2
Er
Pr = r2 ΩA ,
Z

where, Er is the peak electric field at rang, r, and ΩA is the beam solid angle, and Z is the characteristic
of free space, 377 ohms.

The beam solid angle is given by,

4π
ΩA =
D
so that,

2
Er
Pr = 4πr 2
ZD

For the half-wave dipole ("worst case"), directivity D = 1.64. Solving for the radiated power (effective
radiated power referenced to a λ/2 dipole), we find

Pr = 2 MW

Document Created: 2002-04-22 16:00:09
Document Modified: 2002-04-22 16:00:09

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