Comtech EF Data CDM-570AL - Validate Carrier-In-Carrier Performance

CDM-570A/570AL Satellite Modem with Optional Packet Processor
Revision 5
DoubleTalk Carrier-in-Carrier Option G–18 MN-CDM570A
G.4.6 Validate 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.
Comtech EF Data recommends the following steps 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, VersaFEC 0.631 circuit between 4.6 m and 2.4 m antennas
• Recorded Eb/No = 2.7 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.