Comtech EF Data CDM-760 - Page 413

Appendix J Revision 4
CDM-760 Advanced High-Speed Trunking Modem MN-CDM760
J–20
Eb/No = Es/No – 10log(SE) (where SE is Spectral Efficiency)
Es/No
Ratio of Energy per symbol (Es) to Noise density (No) (unit in dB):
Es/No = C/No – 10log(SR) (where SR is the Symbol Rate)
Es/No = Eb/No + 10
log
(SE) (where SE is Spectral Efficiency)
C/N
Ratio of Carrier Power (C) to Noise (N) (unit in dB):
Equivalent to Es/No when calculated in the Symbol Rate
bandwidth.
C/No
Ratio of Carrier Power (C) to Noise Density (N
o
) (unit in dBHz)
Co+No/No
Ratio of Carrier Density (C
o
) + Noise (N
o
) to Noise Density (N
o
) (unit in dB):
C/N = C/N
o
– 10
log
(B) [where B is bandwidth in Hz]
E
b
/N
o
= C/N
o
– 10
log
(DR) [where DR is data rate in bits/sec]
= C/N + 10
log
(B) – 10
log
(DR)
= C/N – 10
log
(SE) (where SE is Spectral Efficiency)
E
b
/N
o
= 10
log
(10
((Co+No/No)/10)
– 1) – 10
log
(SE) (where SE is
Spectral Efficiency)
[Note: Spectral Efficiency is in bps / Hz]
Power Spectral Density (PSD)
Power Spectral Density (PSD) is the signal power per unit bandwidth: dBW / Hz or dBm / Hz
For example: Signal power = 20 dBm
Signal bandwidth = 5 MHz
PSD = 20 – 10 *log (5,000,000)
= -46.99 dBm / Hz
PSD Ratio
Ratio of Power Spectral Density (PSD) of the interfering carrier to the desired carrier.
If looking at the two carriers side-by-side on a spectrum
analyzer: