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42 205486 REV F Operations Manual, HPA2, Compact Outdoor SSPA
5.6 Intermodulation Distortion
Intermodulation distortion is one of the most important characteristics of a solid state power
amplifier system. Satellite communication systems must comply to certain distortion levels
depending on the service involved. All production amplifiers are subjected to automated
intermod testing. This is based on a standard two-tone intermod test in which the intermod
level (IMD) is measured in dBc with respect the main tones and the highest third order
intermod products.
Satcom amplifiers are typically used in some ‘back-off’ condition. This is the operating point at
which the composite output power is ‘backed-off’ from the amplifier’s P
1dB
, compression point.
A curve of back-off vs. IMD level is especially useful in the selection of a power amplifier or
determining the proper output power setting in a Satcom system.
Paradise Datacom recognizes the importance of this back-off characteristic and provides a
plot of back-off Vs IMD from 1 dB to 10 dB back from the amplifier’s compression point.
Figure 5-1 shows a typical back-off curve from a production test set.
Figure 5-1: IMD vs. Backoff for a 50W Ku Band Compact Outdoor SSPA