Validating Carrier-In-Carrier Performance - Comtech EF Data CDM-625 Installation And Operation Manual

CDM-625 Advanced Satellite Modem
DoubleTalk Carrier-in-Carrier Option
10.4.7

Validating Carrier-in-Carrier Performance

Carrier-in-Carrier performance can be easily validated by verifying that Eb/No degradation due
to 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 Task
1
Setup a conventional side-by-side link of the desired Eb/No:
Example Link:
2 Now relocate one of the carriers on top of the other carrier:
3
Calculate change in Eb/No and verify against specification.
Example Link:
 Carrier-in-Carrier should be OFF.
 Record the Eb/No as displayed by the Modems.
 Observe the 2 carriers on a spectrum analyzer and record the PSD ratio.
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)
•
 Enable Carrier-in-Carrier.
 Record the Eb/No as displayed by the Modems.
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
•
10–16
Revision 13
MN-CDM625