R
R
F
F
-
-
8
8
0
0
0
0
0
0
E
E
M
M
i
i
c
c
r
r
o
o
w
w
a
a
v
v
e
e
R
R
F
F
R
R
e
e
p
p
e
e
a
a
t
t
e
e
r
r
— Chapter 3. Mounting the Antennas
RF-8000E Operations Manual
48
Table 13, C/E Requirements per modulation
Modulation Type
Minimum C/E
Isolation
FM Analog, 24 ~ 96 FDM
30 dB
90 dB
FM Analog, 120 ~ 300 FDM
45
105
FM Analog, 420 ~ 2400 FDM
55
115
FM Analog, Color Video
55
115
FSK, MSK
30
90
BPSK 22
92
QPSK, OQPSK, 4PSK, 4QAM
24
84
8PSK 28
88
16QAM 32
92
32QAM 36
96
64QAM 40
100
128QAM 44
104
256QAM 46
106
512QAM 47
107
1024QAM 49
109
2048QAM 50
110
32TCM 35
95
64TCM 39
99
128TCM 43
103
256TCM 46
106
OFDM QPSK
24
84
OFDM 16QAM
32
92
OFDM 64QAM
40
100
COFDM QPSK
24
84
COFDM 16QAM
32
92
COFDM 64QAM
40
100
9QPRS/QPR3 30
90
25QPRS/QPR5 31
91
49QPRS/QPR7 32
92
81QPRS/QPR9 34
94
225QPRS/QPR15 38 98
The leakage signal between antennas acts as a co-channel, like interferer. The time offset or echo
delay is typically close to 200 nanoseconds with 50 feet, 15 meters, of combined feedlines. In
medium to high capacity digital radio systems, this time offset results in intersymbol interference.
Adaptive equalizers can reduce the effects of the echo signal. The objective C/E values listed
assume minimal correction from adaptive equalizers or forward error correction. As a result,
performance may be better than predicted depending on the microwave radio equipment capabilities.
25
For 10dBrnC
0
IM noise, < -1 dB system gain at 10
-6
BER or BER < 10
-12
at normal RSL.
26
Isolation objective assumes a maximum repeater net gain of 60 dB. Isolation required for a specific
C/E decreases dB-for-dB as the maximum gain decreases.