Communications: radio wave antennas – Antennas – Balanced doublet - centerfed
Patent
1982-04-30
1986-09-16
Blum, Theodore M.
Communications: radio wave antennas
Antennas
Balanced doublet - centerfed
343 18E, H04B 7185
Patent
active
046125469
ABSTRACT:
The present invention provides an economical yet effective system for the protection of the command link of ground controlled beacon tracking satellites. The invention includes means for detecting the amplitude and/or phase modulation of a composite signal which results from the beating of an intruder's carrier signal with an uplink beacon. A bandpass filter is included for guaranteeing that the low frequency sweep of the beacon signal and the high frequency data communication signals are passed through the receiver without interference. The resulting output of the bandpass filter corresponds to the intruder's carrier. This signal is rectified to provide a DC signal. A first comparator is provided for comparing the output of the detector to a first threshold which gives an indication as to whether or not the intruder is attempting to saturate an intermediate frequency (IF) stage of the satellite's receiver. A second comparator is provided for comparing the above-identified DC signal to a second threshold. This comparator provides an output which represents the presence of an intruder signal which induces an amplitude or phase modulated composite signal in the preceeding IF amplifier. The comparator outputs are operatively connected to switching means for decoupling the satellite receiver from satellite control circuitry whenever the output of the detector means exceeds the first threshold or the output of the DC rectifier exceeds the second threshold. In effect, the system deactivates the ground base telemetry oriented control mechanism of the satellite whenever an intruder signal is detected which is within a predetermined power range of the beacon tracking signal (stealth) or nearing the saturation limits of the IF amplifier of the satellite receiver (power). This system is therefore effective in providing satellite command link protection against an intruder attempting to acquire control of the satellite by stealth or by power.
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patent: 4349916 (1982-09-01), Roeder
patent: 4355414 (1982-10-01), Inoue
Barron Jr. Gilberto
Benman, Jr. W. J.
Blum Theodore M.
Hughes Aircraft Company
Karambelas A. W.
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