CDM-570A/570AL Satellite Modem with Optional Packet Processor
Revision 5
DoubleTalk Carrier-in-Carrier Option G–36 MN-CDM570A
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 = 2.5 MHz
PSD = 20 – 10 *log (2,500,000) = -43.98 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:
Quasi Error Free (QEF)
Quasi Error Free (QEF) corresponds to PER ~10
-7
[Note: 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]
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