Comtech EF Data CDM-750, Installation And Operation Manual

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CDM-750 Advanced High-Speed Trunking Modem Revision 2
Appendix D MN-CDM750
D–23
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 2 carriers side-by-side on a spectrum
analyzer:
Quasi Error Free (QEF)
Quasi Error Free (QEF) corresponds to PER ~10
-7
PER (packet error rate) is based upon a 188 byte MPEG frame size.
Spectral Efficiency (SE)
Ratio of the Data Rate to the Symbol Rate.
Symbol Rate & Data Rate
Symbol Rate and Data Rate are related:
DR = SR * SE (Data Rate = Symbol Rate * Spectral Efficiency)
SR = DR / SE (Symbol Rate = Data Rate / Spectral Efficiency)