Telecommunications – Use or access blocking
Reexamination Certificate
1985-06-24
2001-08-14
Hellner, Mark (Department: 3662)
Telecommunications
Use or access blocking
C375S333000, C342S373000
Reexamination Certificate
active
06275679
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to the field of communication with a secure data link using a transmitter with a phased antenna array.
There are many forms of secure data links for radio transmission using various types of coding. Although not directed to security, a book by Henning F. Harmuth,
Transmission of Information by Orthogonal Functions,
2nd ed. New York/Heidelberg/Berlin:Springer-Verlag, 1972, is of interest.
Phased array antenna systems are also well known, as shown for example in the text by Skolnik, “Introduction to Radar Systems” 2nd ed. Chapter 8; or in the “Radar Handbook” edited by Skolnik, Chapter 11. U.S. Pat. No. 3,723,955 to Lyons et al discloses a sonar beam generating apparatus in which the generated beam is shifted between 0° and 180° by an array of transducer elements. U.S. Pat. No. 3,697,994 to O'Daniel discloses a digital computer system for steering the pencil beam of a 3-D cylindrical array radar antenna. The beam is steered in both elevation and azimuth by selectively energizing binary phase shifters associated with each radiating element of the array. U.S. Pat. Nos. 4,034,374; 3,646,558; 3,999,182; 3,747,098; 3,478,359; and 3,864,689 disclose a variety of antenna systems with phase shifters which are of general interest.
SUMMARY OF THE INVENTION
An object of the invention is to provide a secure data link, with a radio transmission circuit which permits radiating data signals which are discernible only along the intended path of reception and are unintelligible at other receive points.
The radio transmission circuit according to the invention comprises N antenna elements in a broadside array. A carrier wave is routed to the N elements and the phase to each element is adjusted to direct the transmitted wavefront toward a selected receive point. Prior to transmission, however, the carrier to each element is independently modulated by a two state (0/&pgr;) phase shifter. Each of the 16 carriers is modulated with the first 16 Orthogonal Walsh waveforms (a digital counterpart of the Fourier Transform). The output power levels at all antennas are equal, only the phase of the RF carriers change. Depending upon the sign conditions (inverted or noninverted), for the various 16 modulation waveforms, a pulse position modulation (PPM) signal results; the pulse can occupy one of 16 time positions. This PPM signal will be received clearly at the intended location, however, at other locations, approximately a degree or more to the side of the transmitted direction, the signal will become garbled due to the improper phase relation of the 16 signals arriving at those locations.
A feature of the system is that signals transmitted by broad side array elements which are modulated using two state (0/&pgr;) phase shifters controlled by orthogonal Walsh elements. The Walsh elements are selectively inverted or noninverted in such a manner as to generate a PPM data signal along the intended direction of reception, and produce garbled data to receivers off the signal beam.
REFERENCES:
patent: 3478359 (1969-11-01), Salmon
patent: 3646558 (1972-02-01), Campanella
patent: 3697994 (1972-10-01), O'Daniel
patent: 3701143 (1972-10-01), Nacht
patent: 3723955 (1973-03-01), Lyons et al.
patent: 3747098 (1973-07-01), Kirkpatrick et al.
patent: 3864689 (1975-02-01), Young
patent: 3999182 (1976-12-01), Moeller et al.
patent: 4034374 (1977-07-01), Kruger
patent: 4255810 (1981-03-01), Solomon et al.
patent: 4445119 (1984-04-01), Works
M.I. Skolnik, “Self-Phasing Array Antennas”, IEEE Transactions on Antennas and Propagation, vol. AP-12, 1964, pp. 142-149.
Henning F. Harmuth,Transmission of Information by Orthogonal Functions,2nd ed., New York/Heidelberg/Berlin: Springer-Verlag, 1972, pp. 1-13.
Elam Carl M.
Leavy Dale A.
Franz Bernard E.
Hellner Mark
Kundert Thomas L.
The United States of America as represented by the Secretary of
LandOfFree
Secure communication using array transmitter does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Secure communication using array transmitter, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Secure communication using array transmitter will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2503072