Communications: directive radio wave systems and devices (e.g. – Radar ew – Eccm
Reexamination Certificate
1960-11-16
2001-11-06
Sotomayor, John B. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Radar ew
Eccm
C342S159000, C342S017000, C342S018000
Reexamination Certificate
active
06313782
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to communications systems and particularly to an improved system in which the detectability of the radiated signals by means other than prescribed by the invention is materially reduced, and in which the vulnerability of the system to interfering signals, particularly intentional jamming signals, is substantially reduced.
It will be appreciated that two of the most important factors in a communication system are reliability and privacy of communication. This is particularly so in military communications, either for point to point communication, or in radar applications. It is an absolute essential requirement where the guidance of missiles is concerned. If the privacy of the system is invaded by breaking the code of the system, misleading signals can be radiated to deflect a missile from its target. If reliability is destroyed because of jamming, communications will be interrupted and in this manner a missile prevented from reaching its target.
BRIEF SUMMARY OF THE INVENTION
A particular object of the invention is to provide a communications system which is much less susceptible to interfering or jamming signals than prior art systems.
In the communications system of the invention a radio frequency communications signal is phase modulated by a random or random appearing, but repeatable pattern of noise signal. In accordance with one feature of the invention the phase modulation is between ±90°, or between a reference condition and an inverted or 180° change in phase.
A signal receiver as contemplated by the invention would provide means to modulate (multiply) the received signal by an identical noise signal, which when synchronized with the original noise modulation results in erasing the noise, and thus recreating the original, continuous, communications signal. If a signal other than one modulated by the original noise signal is received, modulation by the receiver results in a wide band spectrum signal for which the receiver resonant circuits are relatively insensitive, as these signals do not have time to normally build up in these circuits.
In radar type systems, the original noise modulation and the receiver modulation are synchronized by means of an adjustable time delay interconnected between the transmitter noise source and the receiver noise source. The measure of delay necessary to obtain synchronization is a measure of the radio path length between the transmitter and the receiver, taking into account, of course, any delay injected by a transponder where the returned signal is reradiated rather than reflected.
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patent: 2175847 (1939-10-01), Mathes
patent: 2268587 (1942-01-01), Guanella
patent: 2406881 (1946-09-01), Young
patent: 2616031 (1952-10-01), Nosker
patent: 2774965 (1956-12-01), DeRosa
patent: 2796602 (1957-06-01), Hess et al.
patent: 2840808 (1958-06-01), Woodward
patent: 2842764 (1958-07-01), Harvey
patent: 2923496 (1960-02-01), Gordon
patent: 2935692 (1960-05-01), Cohen
patent: 2953643 (1960-09-01), Koenig
patent: 2972009 (1961-02-01), Roschke
patent: 3029309 (1962-04-01), Van Jepmond
patent: 3099796 (1963-07-01), Zadoff
Lehan Frank W.
Rechtin Eberhardt
Victor Walter K.
Bush Freddie M.
Sotomayor John B.
The United States of America as represented by the Secretary of
Tischer Arthur H.
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