innovativeness of this method

Primary benefits:  Our closed-loop method enables a transmit array to operate almost as flexibly as adaptive receive-only arrays have been for decades

Specialized Arrays Inc.  700 Wavecrest Ave. Unit 103 Indialantic, Fl 32903

limitations of current methods 

This new technology overcomes the limitations of retrodirective and model-based methods by creating a closed loop with a non-passive (cooperative) source. It features auto-spatial synchronization of the antennas and auto phase/time synchronization of all electronics and fiber.  


It enables a transmit array to operate almost as flexibly as adaptive receive-only arrays have been operating for decades without the limitations and/or complexity of open-loop methods.  Thus, it enables such diverse applications as on-the-move military communications, arraying on a flexing structure such as shipboard, off-shore oil exploration platforms, where smaller antennas could be located on a space-available basis, arraying across very wide distances (1000’s km) where the sensors are not mutually visible, or with additional development arraying mobile high-gain antennas.

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Examples:  Three 12 meter antennas in CA, TX, and FL coherently transmitting to a GEOSAT

Current methods require:

  • Precise (sub-wavelength) position knowledge of the ARP
  •  Control of transmit circuit phase, meaning precision stable hardware or a closed loop means for correcting circuit phase
  • Means for determining unknown differential effects
    • At some frequencies (e.g., X-band and above) and/or locations (e.g., high humidity, or target directions (e.g., low elevation links to a COMSAT), unknown differential propagation effects can seriously degrade beam formation.  If corrected, additional receive circuit calibration, precise knowledge of the target’s position, and sophisticated algorithms are required; an
  • Retrodirective methods require uplink and downlink frequencies that are nearly identical.
    • While this could be possible in a TDMA or radar application, it otherwise makes the method inapplicable for most communication systems, particularly those for satellite communications, which have strictly allocated different bands for receive and transmit.
    • This limitation may be mitigated by slightly offsetting receive and transmit frequencies, but the further apart array elements are in wavelengths, the more serious error develops, with even very small offset resulting in significant beamforming errors.​
  •  Additionally retrodirective receivers must contend with the transmitter output coupling into the receive path, with contribution potential for oscillation, and with noise.
    • This limits both the maximum output power (before oscillation) and the weakest signal that can be received due to transmitter noise. 
  • Other issues with retrodirectivity include latency and deficiencies with sensing and adjustment: Latency is an issue for remote targets, in that target motion can result in the return beam going to where the target was, not where it is.  In other words, look-ahead beam pointing is not possible in general.  Also, when beam shaping and sidelobe control is important (e.g., LPI and LPD), retrodirectivity has no means for sensing and adjustment.

very widely spaced cooperative source transmit array

SAI patent-pending technology

Benefits of SAI very widely spaced transmit arraying system

(1)  Does not require line-of-sight between the antennas 

(2)  Precision hardware and/or specialized hardware and algorithms to control circuit phase are not required since system is a long closed loop

  • Reduced expense

(3)   Low power requirements of individual dishes on transmit mitigates discovery

(4)   Inherent redundancy:  Handles element failures

(5)   Receive:   up to 3dB G/T increase each time the number of elements is doubled 

(6)   Transmit:  up to 6dB EIRP increase each time the number of elements is doubled

(7   Patent-pending closed-loop method avoids the numerous limitations of retrodirective methods

(8)  Flexible array configuration

Click to enlarge

Definition:  An array of very widely spaced ground reflectors used to coherently transmit to a 'Near Earth' target such as a typical COMSAT, (WGS, DSCS).    A cooperative target is used that can feedback a measure of the transmit performance, and is a cooperative receiver, a bent-pipe, or a reflector.

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coherent transmit to a COMSAT   -   attribution avoidance