Alcatel-Lucent 9500 MXC, User Manual, Page: 319 / 916

9500 MXC User Manual
3DB 23063 ADAA - Rev 004 July 2007 Vol. III-5-19
Figure 5-3.
Indicative head-on signal pattern for a parabolic antenna
Tracking Path Error
Side lobe signal readings can be confused with main beam readings. This is
particularly true for the first side lobe as the signal level at its center is greater
than the signal level at the edges of the main beam, and if tracking on an incorrect
elevation (or azimuth) a false impression of main beam reception can be
obtained. Figure 5-4 shows an example of this with a simplified head-on view of
an antenna radiation pattern, and tracking paths for three elevation settings.
Figure 5-4.
Example Tracking Path Signals
Line AA represents the azimuth tracking path of a properly aligned antenna. The
main beam is at point 2, and the first side lobes at points 1 and 3.
Center of main beam provides
maximum signal level
Outer edge of main beam, 3-10 dB
below main beam
Trough between main beam and first
side lobe, 30 dB below main peak
Peak of 1st side lobe, 20-25 dB
below main peak
Trough between first and second side
lobes, 30 dB or more below main peak
Subsequent side lobe peaks and troughs
Head-on View
A
B
C C
B
A
6 7 7
1 2 3
4 5
6 7
4 5
1
2 2
3
Head-on View of Azimuth Tracking
Paths for Different Elevations
Signal Levels for Each Track
C C
B B
A A