Page
All Rights Reserved Shyam Telecom Limited
30/43
Next Generation
Signal Enhancement
•
Antenna with proper characteristics to maintain adequate isolation
to avoid oscillations. Normally, isolation should be 15 dB more
than the gain set for the repeater. It should have good front to
back ratio.
•
The beam width for the DONOR antenna should be as small as
possible.
•
The beam width for SERVER antenna is 60 degree to 120 degree.
•
There should be adequate vertical & horizontal separation
between the DONOR & SERVER antennas to avoid interference
and noise.
Separation can be determined by the mathematical formulas:
Vertical Separation:
Isolation (dB) = 28 + 40 log (D/
λ
in meters)
Horizontal Separation:
Isolation (dB) = 22 + 20 log (D/
λ
in meters) – (Gain of donor
a gain of server antenna)
D-Distance between donor & server antennas in meters
λ
- Wave length in meters
The following table is an approximate guide to antenna separation.
The use of highly directional antennas with good front to back ratios can
help to achieve isolation requirements.
A Typical Example
Vertical Separation
Separation (m.)
Isolation (dB)
5 75.0
10 87.1
20 99.1
30 106.2
40 111.2
50 115.0
Horizontal Separation
Separation (m.)
Isolation (dB)
5 45.5
10 51.7
50 65.5
100 71.5
150 75.1
250 77.6
Vertical and Horizontal Antenna Separation @ 900 MHz
The antenna separation table demonstrates that vertical separation yields
better results than horizontal separation. However, when desired isolation
cannot be met due to insufficient separation, external shielding can help; for
example, mounting the antennas on either side of a rooftop penthouse or
