Microwave self-phasing antenna arrays for secure data transmission & satellite network crosslinks

• US 20050030226A1
• Filed: 08/04/2004
• Published: 02/10/2005
• Est. Priority Date: 08/05/2003
• Status: Active Grant

• Current Assignee: University of Hawai'i
• Original Assignee: University of Hawai'i
• Inventors: Ohta, Aaron, Miyamoto, Ryan Y., Tamamoto, Michael, Shiroma, Wayne A., Shiroma, Grant S., Murakami, Blaine T.
• Granted Patent: US 7,006,039 B2
• Time in Patent Office: Days
• US Class Current: 342/370
• CPC Class Codes: H01Q 1/22 by structural association with other equipment or articles
• CPC Class Codes: H01Q 1/288 Satellite antennas
• CPC Class Codes: H01Q 3/2652 Self-phasing arrays
• CPC Class Codes: H04K 2203/14 for the transfer of light or images, e.g. for video-surveillance, for television or from a computer screen
• CPC Class Codes: H04K 2203/18 for wireless local area networks or WLAN
• CPC Class Codes: H04K 2203/22 for communication related to vehicles
• CPC Class Codes: H04K 2203/32 including a particular configuration of antennas
• CPC Class Codes: H04K 3/224 with countermeasures at transmission and/or reception of the jammed signal, e.g. stopping operation of transmitter or receiver, nulling or enhancing transmitted power in direction of or at frequency of jammer
• CPC Class Codes: H04K 3/28 with jamming and anti-jamming mechanisms both included in a same device or system, e.g. wherein anti-jamming includes prevention of undesired self-jamming resulting from jamming
• CPC Class Codes: H04K 3/43 characterized by the control of the jamming power, signal-to-noise ratio or geographic coverage area
• CPC Class Codes: H04K 3/825 by jamming
• CPC Class Codes: H04K 3/92 related to allowing or preventing remote control
• CPC Class Codes: Y02A 40/28 specially adapted for farming

Abstract

A high-directivity transponder system uses a dual system of a retrodirective array transmitting a data signal peak toward an interrogator source, and a self-null-steering array transmitting a null toward the interrogator source and a jamming signal elsewhere, resulting in high S/N reception at the interrogator source and avoidance of interception. Integrating modulators would allow each array to transmit different data while the spectra of the transmitted signals are identical, thus disabling interception. The system enables secure point-to-point communications and can be used for short-distance wireless data transmission systems such as wireless LAN and RFID servers. As another aspect, self-steering signal transmission is employed for randomly oriented satellites using circularly polarized, two-dimensional retrodirective arrays. Quadruple subharmonic mixing is used as an effective means of achieving phase conjugation when a high-frequency LO is not feasible or inapplicable. These features may be used for small-satellite communications, secure tactical communications, search and rescue, enemy location fixing and tracking, UAV command and control, forest fire detection, marine-based tracking, and many other applications requiring secure communications with high signal directivity.

Claims

1. A secure data transmission system for transmitting a data signal with high directivity toward a target while greatly reducing the likelihood of interception, comprising:

(a) a self-phasing retrodirective array for receiving an interrogating signal from the target and transmitting a data signal beam with a peak directed back toward the target; and

(b) a self-null-steering array for receiving the interrogating signal from the target and transmitting, in conjunction with said retrodirective array, a jamming signal with a null directed toward the target and the jamming signal in other directions,

whereby the target can receive the data signal peak superimposed with the jamming signal null to maximize signal-to-noise (SNR) ratio in reception while the jamming signal is sent in the other directions.

2. A secure data transmission system according to claim 1, wherein said retrodirective array has self-phasing elements arranged in one layer, and said self-null-steering array has self-phasing elements arranged in another layer in tandem with the retrodirective array.

3. A secure data transmission system according to claim 1, wherein said retrodirective array has self-phasing elements integrated with self-phasing elements of said self-null-steering array in a common circuit layout.

4. A secure data transmission system according to claim 1, wherein said retrodirective array and said self-null-steering array are arranged to send a data signal peak and a jamming signal null with a SNR in the range of 20 dB or greater toward the interrogating target.

5. A secure data transmission system according to claim 1, wherein said self-null-steering array has self-phasing elements and a phase-conjugating circuit comprised of Schottky diodes mounted oppositely at each self-phasing element of the array, so that current flows in opposite directions while a local oscillator (LO) signal is applied in phase.

6. A secure data transmission system according to claim 1, wherein the dual array system is applied for data transmission in a short-distance wireless data transmission system.

7. A secure data transmission system according to claim 1, wherein the dual array system is applied for data transmission in a satellite TV system transmitting a narrow beam over a wide area to prevent piracy of TV signals in regions surrounding a target region.

8. A secure data transmission system according to claim 1, wherein the dual array system is applied for secure data transmission in any one of the group of applications consisting of:

(a) nanosatellite communications;

(b) secure tactical communications;

(c) search and rescue location fixing and tracking;

(d) military target location fixing and tracking;

(e) unmanned aerial vehicle (UAV) command and control;

(f) forest fire detection;

(g) marine-based tracking; and

(h) another application requiring secure communications with high signal directivity.

9. A secure data transmission method for transmitting a data signal with high directivity toward a target while greatly reducing the likelihood of interception, comprising:

(a) employing a self-phasing retrodirective array to receive an interrogating signal from the target and transmit a data signal beam with a peak directed back toward the target; and

(b) employing a self-null-steering array to receive the interrogating signal from the target and transmit, in conjunction with said retrodirective array, a jamming signal with a null directed toward the target and the jamming signal in other directions,

whereby the target can receive the data signal peak superimposed with the jamming signal null to maximize signal-to-noise (SNR) ratio in reception while the jamming signal is sent in the other directions.

10. A secure data transmission method according to claim 9, wherein said data signal peak and jamming signal null are sent with a SNR in the range of 20 or greater toward the interrogating target.

11. A system for secure crosslink communications in a network of small-platform transponders moving randomly in space, comprising:

(a) a plurality of small-platform transponders each having a retrodirective antenna array for detecting the direction of an incoming interrogator signal and sending a response signal with a peak directed back toward the direction of the interrogator signal; and

(b) said plurality of small-platform transponders operating together as a network of transponders by each one of said transponders establishing and maintaining a reliable crosslink with the other transponders without a priori knowledge of their positions by intermittently sending an interrogator signal to one or more other transponders and having the one or more other transponders send a response signal back to the one transponder.

12. A system for secure crosslink communications in a network of small-platform transponders according to claim 11, wherein said network of transponders is a network of small-satellites in low earth orbit.

13. A system for secure crosslink communications in a network of small-platform transponders according to claim 12, wherein said network of small-satellites are nanosatellites in the 10 kg weight range and/or picosatellites in the 1 kg weight range.

14. A system for secure crosslink communications in a network of small-platform transponders according to claim 11, wherein the retrodirective array of each one of the transponders is configured for circularly polarized, two-dimensional steering.

15. A system for secure crosslink communications in a network of small-platform transponders according to claim 11, wherein said network of transponders is applied for secure data transmission for any one of the group of missions consisting of:

(a) passive radiometry mission for high accuracy geolocation;

(b) cluster augmentation for reliable data transmission on demand;

(c) radar mission in locating and fixing targets; and

(d) communications mission in narrow-beam, wide-area coverage.

16. A system for secure crosslink communications in a network of small-platform transponders according to claim 11, wherein said network of transponders is applied for secure data transmission in any one of the group of applications consisting of:

(a) nanosatellite communications;

(b) secure tactical communications;

(c) search and rescue location fixing and tracking;

(d) military target location fixing and tracking;

(e) unmanned aerial vehicle (UAV) command and control;

(f) forest fire detection;

(g) marine-based tracking; and

(h) another application requiring secure communications with high signal directivity.

17. A system for secure crosslink communications in a network of small-platform transponders according to claim 11, wherein each one of said network of transponders has a retrodirective array with 8 self-phasing elements arranged in a planar cross configuration, with 4 elements aligned in each orthogonal planar direction.

18. A system for secure crosslink communications in a network of small-platform transponders according to claim 11, wherein each one of said network of transponders has a dual array system including a self-phasing retrodirective array for receiving an interrogating signal and transmitting a data signal beam with a peak directed back toward the interrogator position, and a self-null-steering array for receiving the interrogating signal and transmitting, in conjunction with said retrodirective array, a jamming signal with a null directed toward the interrogator position.

19. A method for secure crosslink communications in a network of small-platform transponders moving randomly in space, comprising:

(a) providing each transponder in the network of small-platform transponders with a retrodirective antenna array for detecting the direction of an incoming interrogator signal and sending a response signal with a peak directed back toward the direction of the interrogator signal; and

(b) operating the network of small-platform transponders together by each one of said transponders establishing and maintaining a reliable crosslink with the other transponders without a priori knowledge of their positions by intermittently sending an interrogator signal to one or more other transponders and having the one or more other transponders send a response signal back to the one transponder.

20. A method for secure crosslink communications in a network of small-platform transponders according to claim 19, wherein said network of transponders is a network of small-satellites in low earth orbit.