Intermodulation Spectra for Two SCPC Systems

Carrier-to-intermodulation (C/IM) power ratios are derived for two types of single-channel-per-carrier (SCPC) systems in terms of the single-carrier transfer characteristic of the satellite TWT. The first system is based on a set of equal-amplitude, uniformly spaced carriers and is appropriate whenever complete earth-station interconnectivity is required in a bandwidth-limited environment. The second system is designed to handle traffic flow between a large number of small stations and one or more large stations. It utilizes a frequency plan of alternating large and small carriers. The C/IM ratios for the twolevel system are expressed in terms of the C/IM ratio for a single-level system operating at the same TWT backoff. Application of the results to a power limited system of either type is also indicated.