Belden 942 047-001, Руководство пользователя

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64
BAT Antenna Guide BAT
Release 09 05/2015

Decibels (dB)
The remaining output of an antenna at a specific angle is shown in
negative decibels (dB) on the antenna diagram.
See “Interpreting antenna diagrams” on page 64.
How do you interpret the negative decibel values on the antenna
diagram?
Definition dB: Q
(P)
= 10 × lg
10
P
1
/P
2
dB
The following table shows the attenuation in steps of
− 3 dB:
In antenna diagrams, circles are used to display the attenuation – usually
in steps of 10:
Example:
The above antenna diagram shows the output at
− 30° as − 10 decibels.
Omni-directional antenna,
horizontal cross-section,
antenna viewed from above Omni-directional antenna, vertical cross-section,
antenna viewed from the side
Table 72: Interpreting antenna diagrams
Attenuation in
decibels Remaining output
− 3 1/2
− 6 1/4
− 9 1/8
− 12 1/16
Attenuation in
decibels Remaining output
− 10 1/10
− 20 1/100
− 30 1/1000
− 40 1/10 000
180
150
120
90
60
30
0
-30
-60
-90
-120
-150
0 -10 -20 -30 -40
180
150
120
90
60
30
0
-30
-60
-90
-120
-150
0 -10 -20 -30 -40
in all angles ca. 0 dB
180
150
120
90
60
30
0
-30
-60
-90
-120
-150
0 -10 -20 -30 -40
180
150
120
90
60
30
0
-30
-60
-90
-120
-150
0 -10 -20 -30 -40
main lobe (0 dB) main lobe (0 dB)
side lobe (-10 dB) side lobe (~ -12 dB)
side lobe (~ -9 dB) side lobe (~ -11 dB)