초록 ▼

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 i

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. One mobile may send a broadcast interrogator signal, causing the other mobile devices to send a reply signal back to the interrogating mobile device only in the direction of the interrogating mobile device, such that each of the other mobile devices identifies its position to only the interrogating mobile device in response to its broadcast interrogator signal. 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.

대표청구항 ▼

The invention claimed is: 1. A method for secure crosslink communications in a network of mobile devices having respective signal transponders which are moving in non-fixed positions relative to each other in space, comprising: (a) causing one mobile device to send a broadcast interrogator signal t

The invention claimed is: 1. A method for secure crosslink communications in a network of mobile devices having respective signal transponders which are moving in non-fixed positions relative to each other in space, comprising: (a) causing one mobile device to send a broadcast interrogator signal to the other mobile devices in the network; (b) causing each of the other mobile devices to send a reply signal back to the interrogating mobile device only in the direction of the interrogating mobile device, such that each of the other mobile devices identifies its position to only the interrogating mobile device in response to its broadcast interrogator signal. 2. A method according to claim 1, wherein the network of mobile devices is a network of small satellites in low earth orbit. 3. A method according to claim 2, wherein the network of small satellites are of a size from nanosatellites in the 10 kg weight range to picosatellites in the 1 kg weight range. 4. A method according to claim 1, wherein each mobile device has a signal transponder provided with a retrodirective antenna array for detecting the direction of an incoming interrogator signal, and for sending a reply signal with a peak directed back toward the direction of the interrogator signal and a null or jamming signal in all other directions. 5. A method according to claim 4, wherein each one of said signal transponders has a dual array system including a self-phasing retrodirective array for receiving the interrogator signal and transmitting a reply signal with a peak directed back toward the position of the interrogating mobile device, and a self-null-steering array for receiving the interrogator signal and transmitting, in conjunction with said retrodirective array, a jamming signal in other directions and a null directed toward the position of the interrogating mobile device. 6. A method according to claim 1, wherein the network of mobile devices is used for secure data transmission in 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. 7. A method according to claim 1, wherein the network of mobile devices is used 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. 8. A method according to claim 1, wherein each of the mobile devices in the network is scheduled in turn to send a broadcast interrogator signal to the other mobile devices in the network, so that each mobile device becomes apprised of the positions of the other mobile devices relative to it and can send secure communications only in the directions of the other mobile devices. 9. A method according to claim 1, wherein each one of said signal transponders is a retrodirective array with 8 self-phasing elements arranged in a planar cross configuration, with 4 elements aligned in each orthogonal planar direction.