Spurious signal analysis of a communications satellite repeater

The procedures used to determine the spurious signal outputs of a communications satellite repeater are discussed. It is shown that a spurious output can be resolved into a spurious source power multiplied by the gain or loss of a Transmission Factor (TF), which is the gain/loss of the spurious signal in dBs. Loss sources include: active waveguide attenuation; physical and/or electrical isolation; and filtering. Gain sources include receivers, driver amplifiers, and traveling-wave tubes (TWTs). The TF may be calculated directly from the communications telemetry command gain budget if the spurious signal transmission path is due to multiple transmission paths having similar sources. The techniques used to reduce spurious signal outputs are also discussed, including: harmonic filtering; receive-band reject filtering; and receiver bandpass filtering. A computer program written in MBASIC to calculate spurious outputs is given in an appendix.