DMD20/20LBST Universal Satellite Modem
Theory of Operation
MN-DMD20-20LBST Revision 14
3–45
Power Equivalent Bandwidth
Power Equivalent Bandwidth (PEB) is the transponder power used by a carrier, represented as
bandwidth equivalent.
PEB Calculation Example:
•
Transponder EIRP = 37 dBW
•
Output Backoff (OBO) = 4 dB
•
Available EIRP = 37 – 4 = 33 dBW = 10
3.3
= 1955.26 Watts
•
Transponder Bandwidth = 36 MHz
•
Power Available / MHz = 1955.26 / 36 = 54.424 W
•
If a carrier uses 24 dBW, its PEB = 10
2.4
/ 54.424
= 4.532 MHz
This corresponds to 12.59% of available transponder power.
Leased bandwidth
Almost all satellite operators charge for the Leased Bandwidth (LBW). Leased Bandwidth or
Leased Resource is the greater of the Allocated Bandwidth and Power Equivalent Bandwidth.
For example, if a carrier requires 3 MHz of Allocated BW and 4.5 MHz of PEB, the Leased
Bandwidth is 4.5 MHz
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 = 500 kHz
PSD = 20 – 10 *log (500 * 1000)
= -36.99 dBm / Hz
PSD Ratio
PSD ratio is the ratio of power spectral density of
the interfering carrier and the desired carrier. If
looking at the 2 carriers side-by-side on a
spectrum analyzer:
Eb/No
Ratio of Energy per bit (Eb) to Noise density (No): Unit is dB
C/N
Carrier Power (C) to Noise (N) ratio: Unit is dB
C/No
Carrier Power (C) to Noise Density (N
o
) ratio: Unit is dBHz