Comtech EF Data CDM-750 - Manual (Page 277)

CDM-750 Advanced High-Speed Trunking Modem Revision 2
Appendix D MN-CDM750
D–19
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)
CnC Ratio from C/N
C/N (dB) Symbol Rate (Msps) CnC Ratio (by Carrier Direction)*
Link 1 Link 2
SR
Link 1
SR
Link 2
CnC A
(Site A Æ Site B)
CnC B
(Site B Æ Site A)
9.5 7.5 5.0 6.5 +0.86 dB -0.86 dB
* 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