A new method for coherent transmit arraying that offers quick setup, wider spacing, and new mission capabilities has been the focus of SAI IR&D since 2011. This technology is designed for use with closer targets (rather than deep space), such as Earth-orbiting satellites. It creates a closed-loop with a non-passive (cooperative) source and features auto-spatial synchronization of the antennas and auto phase/time synchronization of all electronics and fiber.
In a tactical communications environment, this technology enables quick deployment of smaller antennas, each with lower power amplifiers collectively enabling coherent transmission of large amount of data, since array EIRP increases as the number of elements squared.
Another application of this system is communication with a GEO satellite from an array of ground reflectors. They can be widely-spaced such as 100's of meters or 1000's of kilometers. The only requirement is that the cooperating target be in the beam of each of the individual antennas. With this method, large amounts of data can be sent from the ground antenna array to a satellite without the need for surveying the antenna reference points of each of the individual antennas and without the need for precise knowledge of circuit or propagation phase differentials.
Dispersal of smaller antennas coherently transmitting make individual element targeting difficult since the array phase center need not correspond with any given antenna, and since searching for the transmission source using AOA may fail due to the sensor being in the array's near field. The low power amplifiers increase the difficulty of accurately locating individual antennas in the array's locality.
The array provides built-in redundancy in the event one is put out of service; the others continue to send the data up to the target. This is useful for battlespace awareness applications.
Another mission application is SSA.
NASA has estimated there are more than 20,000 larger than a softball, 500,000 larger than a marble, and millions so small they cannot be tracked. See “Space Debris and Human Spacecraft” (Sept 26, 2013). ESA as of July 25, 2013 has estimated there are 29,000 larger than 10 cm, 670,000 larger than 1 cm, and more than 170 million larger than 1 mm. The Air Force (SSN) believes there are more than 21,000 objects larger than l0 cm, 500,000 between 1 and l0 cm.
A 10 cm object could destroy a satellite, a 1 cm object could disable a spacecraft, and a 1 mm object could destroy a sub-system on a spacecraft. The greatest concentration of orbital debris is thought to be around 800-850 km, with most within 2000 km from the Earth. This is the LEO orbit. As of October of 2013, it was reported in Universe Today that there were 1071 operational Earth-orbiting satellites. About 50% were launched by the United States of America. In as few as 50 years, upper LEO and lower MEO may be unusable due to space junk.
Definition: Small antennas that can be quickly arrayed in rugged environments and used for transmission and reception
Benefits of arrays of small dishes
(1) Quick setup and breakdown
(2) Low power requirements on transmit mitigates discovery
(3) Inherent redundancy: Handles element failures
(4) Receive: up to 3dB G/T increase each time the number of elements is doubled
(5) Transmit: up to 6dB EIRP increase each time the number of elements is doubled
(6) Patent-pending closed-loop method avoids the numerous limitations of retrodirective methods
(7) Simultaneous links: Multiple link support
(8) Flexible array configuration
(9) Method is applicable to larger dishes
(10) No surveying of antenna reference points is required; instantly ready
Examples: Soldier/squadron on-the-move can uplink high bandwidth video data of their surroundings avoiding discovery due to the low power required of each small dish
Primary benefits: In environments where a single large dish is a 'target' many small ones can be arrayed together to act as one larger one.
Man-portable, quick deployable coherent uplink array for high bandwidth uplink
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