The Satellite Ferrimagnetic Power Limiter
01 July 1963
The traveling-wave tube 1 in the Telstar communications repeater 2 serves to amplify both the 4170-mc output signal and the low-level (--12 dbm) 4080-mc local oscillator-beacon signal. The T W T gain for the 4080-mc signal is strongly dependent upon the 4170-mc signal level. If the signal to the satellite is lost, no 4170-mc signal is generated and the gain for the 4080-mc signal increases significantly. Additionally, temperature variations can cause undesired level changes. As can be seen from Fig. 1 of Ref. 2, the 4080-mc signal is the local oscillator for the beat oscillator modulator, which generates the 6300-mc local oscillator signal for the input down converter. This increased 4080-mc level can cause the modulator to oscillate. To eliminate these effects a microwave ferrimagnetic power limiter was designed and incorporated to limit the 4080-mc level. Because this type of limiter incorporates a resonant cavity, it serves a required filter func1817 1818 T H E BELL SYSTEM TECHNICAL J O U R N A L , JULY