Comtech EF Data CDM-750 Installation And Operation Manual page 275

CDM-750 Advanced High-Speed Trunking Modem
Appendix D
D.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
Link 2
Link 1
7.5 5.0
D–19
CnC Ratio (by Carrier Direction)*
SR CnC A
Link 2 (Site A Site B)
6.5 +0.86 dB
Revision 2
MN-CDM750
CnC B
(Site B Site A)
-0.86 dB