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CDM-750 High Speed Trunking Modem
DoubleTalk Carrier-in-Carrier Option
8.5.2.2
Calculating CnC Ratio from Carrier to Noise Ratio (C/N) on a
Spectrum Analyzer
For this example, assume Site A is running a
link to Site B (referred to as Link 1), and Site
B is running a link to Site A (referred to as
Link 2):
•
CnC Ratio = C/N Interferer – C/N Desired + 10log(SR Interferer /
SR_Desired)
•
CnC Ratio at Site A = C/N Link 1 – C/N Link 2 + 10log(SR Link 1 /
SR Link 2)
•
CnC Ratio at Site B = C/N Link 2 – C/N Link 1 + 10log(SR Link 2 /
SR Link 1)
C/N (dB)
Link 1
9.5
* Notes:
•
From the standpoint of Site A:
CnC Ratio = 9.5 – 7.5 + 10log(5.0 / 6.5) = +0.86
•
From the standpoint of Site B:
CnC Ratio = 7.5 – 9.5 + 10log(6.5 / 5.0) = -0.86
CnC Ratio from C/N
Symbol Rate
(Msps)
SR
SR
Link 2
Link 1
Link 2
7.5
5.0
6.5
CnC Ratio
(by Carrier Direction)*
CnC A
CnC B
(Site A
Site B)
(Site B
+0.86 dB
-0.86 dB
8–17
Revision 1
MN-CDM750
Site A)
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