Comtech EF Data CDM-625A - Manual (Page 622)

CDM-625A Advanced Satellite Modem MN-CDM625A
Appendix F Revision 3
F–16
F.2.7 Validate Carrier-in-Carrier Performance
You may easily validate Carrier-in-Carrier performance by verifying that Eb/No degradation due
to Carrier-in-Carrier is within published specification for the observed Power Spectral Density
Ratio.
Comtech EF Data recommends that you do these steps to validate CnC 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:
o Full duplex 512 kbps, QPSK, LDPC 2/3 circuit between 4.6 m and 2.4 m antennas
o Recorded Eb/No = 2.6 dB (at both modems)
o 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:
o Recorded Eb/No = 2.4 dB
o Change in Eb/No = 0.2 dB
o Eb/No Degradation (Spec.) at 1.2 dB PSD = 0.3 dB
o Modem performance is within spec