Teledyne 6 RU Chassis, Operation Manual

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78 202058 REV AA 6 RU SSPA Chassis Operations Manual
4.1 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.
Teledyne 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 4-2 shows a typical back-off curve from a production test
set.
Figure 4-2: IMD vs. Backoff for a 50W Ku Band Compact Outdoor SSPA