7 validating carrier-in-carrier performance – Comtech EF Data SLM-5650A User Manual
Page 314

SLM5650A_CDM625 Satellite Modem
Revision 8
DoubleTalk
Carrier-in-Carrier Option
MN-SLM5650A
15–16
15.4.7 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 procedure is recommended for validating Carrier-in-Carrier performance:
Step Task
1
Setup a conventional side-by-side link of the desired Eb/No:
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.
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)
2
Now relocate one of the carriers on top of the other carrier:
Enable Carrier-in-Carrier.
Record the Eb/No as displayed by the Modems.
3
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