Comtech EF Data DMD-2050E - Manual (Page 86)

DMD2050E Universal Satellite Modem Theory of Operation
MN-DMD2050E Revision 2 3–44
3.11.11 Validating Carrier-in-Carrier Performance
Carrier-in-Carrier performance can be easily validated by verifying that Eb/No degradation because of
Carrier-in-Carrier is within published specification for the observed Power Spectral Density Ratio.
The following steps are recommended for validating Carrier-in-Carrier performance:
Step Procedure
1a Set up a conventional side-by-side link of the desired Eb/No:
1b Carrier-in-Carrier should be OFF.
1c Record the Eb/No as displayed by the Modems.
1d Observe the 2 carriers on a spectrum analyzer and record the PSD ratio.
Example Link:
Full duplex 512 kbps, QPSK, LDPC 2/3 circuit between 4.6 m and 2.4 m antennas
Recorded Eb/No = 2.6 dB (at both modems)
PSD Ratio = 1.2 dB (measured at larger Antenna)
2a Now relocate one of the carriers on top of the other carrier.
2b Enable Carrier-in-Carrier.
2c Record the Eb/No as displayed by the Modems.
3a Calculate change in Eb/No and verify against specification.
Example Link:
Recorded Eb/No = 2.4 dB
Change in Eb/No = 0.2 dB
Eb/No Degradation (Spec.) at 1.2 dB PSD = 0.3 dB
Modem performance is within spec.