P
P
E
E
S
S
1
1
9
9
0
0
0
0
G
G
i
i
G
G
S
S
M
M
R
R
e
e
p
p
e
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a
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PES1900NR Operations Manual
Chapter 3. Mounting the Antennas — 39
The equation for antenna isolation is:
ISO = P
GEN
– L
C-GEN
+ L
C-SA
- P
SA
Where:
ISO = Isolation in dB between the antennas.
P
GEN
= Output level of the signal generator (dBm).
L
C-GEN
= Loss of the signal generator cable (dB).
L
C-SA
= Loss of the spectrum analyzer cable (dB).
P
SA
= Power indicated on the spectrum analyzer (dBm).
This equation holds true for one donor antenna, and for one vertically-polarized subscriber antenna.
For a dual-polarized antenna, the equation becomes:
ISO = P
GEN
– L
C-GEN
+ L
C-SA
– MAX(P
SA_L
, P
SA_R
)
Where:
P
SA_L
= Spectrum analyzer level measured on the left antenna port.
P
SA_R
= Spectrum analyzer level measured on the right antenna port.
The stronger of the two readings represents the actual isolation available. For example:
P
GEN
= 10 dBm
L
C-GEN
= 1.0 dB
L
C-SA
= 1.0 dB
P
SA_L
= -90 dBm
P
SA_R
= -88 dBm
ISO = 10 dBm – MAX(-90 dBm or –88 dBm) = 98 dB
NOTE:
A signal level of –88 dBm is stronger than a level of –90 dBm.
In this example, the usable antenna isolation is 98 dB. Antenna isolation of 98 dB will support a
repeater gain setting of 83 dB or less; (98 – 15) = 83.