24 GHz antenna gain measurements part
1
Introduction:
After having some success with 10 GHz measurements and getting curious
about our 24 GHz antennas we decided that it was time to get the 24 GHz
system working. The available measurement system was limited to 18 GHz.
Some work had to be done to fool the system.
Antennas:
In total there were six different feed dish combinations. One dish was
tested with three different feeds.
|
PA3CEG DBS
|
PA3CEG 90cm chaparral feed
|
-
|
|
PE1AEO procom dish and feed
|
PE1AEO Bendix dish with procom feed
|
-
|
|
PE1CQQ procom feed
|
PE1CQQ dish-feed
|
PE1CQQ chaparral feed
|
|
PE1CQQ offset dish
|
|
|
Procedure:
First a measurement was done with a standard gain horn. These results were
used for determine a correction factor. This correction factor is used
for calculating the gain of the antenna under test. After that the antenna's
were measured by taking an azimuth scan increasing the elevation angle
and taking an other scan again.
On the receiver side two measurements are simultaneous done. The first
one is the signal received by the test antenna. The second one is the signal
received by a reference antenna which is pointed to the transmit antenna
and not moved during the whole measuring session. Any drift in the transmitter/receiver
or change in path loss are canceled out in this way. This reference measurement
is done a couple of times during the whole session.
Results:
|
Antenna
|
D (m)
|
f/D
|
Gain (dBi)
|
Eff (%)
|
Azimuth
|
Elevation
|
3D
|
Contour
|
|
PA3CEG DBS
|
0.35
|
|
|
|
-
|
-
|
-
|
-
|
|
PA3CEG 90cm chaparral feed
|
0.90
|
|
.. (44.1)
|
|
-
|
-
|
-
|
-
|
|
PE1AEO procom dish and feed
|
0.45
|
0.4
|
.. (38.1)
|
|
-
|
-
|
-
|
-
|
|
PE1AEO Bendix dish with procom feed
|
0.46
|
0.48
|
.. (38.3)
|
|
-
|
-
|
-
|
-
|
|
PE1CQQ procom feed
|
0.45
|
0.28
|
.. (38.1)
|
|
-
|
-
|
-
|
-
|
|
PE1CQQ dish-feed
|
0.45
|
0.28
|
.. (38.1)
|
|
-
|
-
|
-
|
-
|
|
PE1CQQ chaparral feed
|
0.45
|
0.28
|
.. (38.1)
|
|
-
|
-
|
-
|
-
|
|
PE1CQQ offset dish
|
0.55
|
|
.. (39.9)
|
|
-
|
-
|
-
|
-
|
Gain is measured gain. Between brackets the theoretical gain @ 50%
efficiency.
Graphs are produced by a matlab postprocession.
Conclusions:
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(c) PE1CQQ Last update 27-6-2001