Radically new approach for Large Antenna in Space:

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• Radically new approach for Large Antenna in
  Space
• The Rf Prism concept
• JEAN PAUL AGUTTES
• Presented by Amir-Shwartz

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Agenda

• Motivation Constrain
• Possible solutions
• Theoretical background
• Concept description
• Concept Implementation
• Possible Applications
• Conclusions
• Future Research

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Motivation Constraint

• Market demands
• Telecom missions from space in RF bands
• Cellular phones, P-band Radar, high resolution
  passive imaging
• Geostationary orbit eavesdropping
• Mission Requirement
• These missions require deployment of large
  aperture Antennas in space (gt20 M)

• Constraint
• Large aperture antennas are sensitive to
  contractual deformation and weight to much for
  satellites

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Possible Solutions

• Membrane Umbrella using Membrane as a
  reflector and Umbrella mechanics reflectors as
  in Inmarsat 4 and Guranda satellite.
• Deformation Correction sensing the deformation
  and correcting the feed position- requires an
  active feed system
• Antenna array sensitive to misalignment in the
  array plane
• Smart antenna array perform heavy real time
  digital beam forming that requires a lot of
  present and future sharp technology
• RF lens require additional satellite in very
  close range (lt50 M) which is a difficult
  requirement
• RF Prism Lets see.

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Theoretical background- Reflector antennas (1)

• Parabolic reflector antenna Gain
• The efficiency for parabolic antenna is given by

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Theoretical background- Reflector antennas (2)

• Performances depended on
• Ration of Power collected by the reflector
• Power of the feed
• Amplitude of the field extent of uniformed
  distribution on the reflector surface
• Phase of the field extent of uniformed
  distribution on the reflector surface
• Polarization of the field extent of uniformed
  distribution on the reflector surface
• Blockage efficiency
• Random error efficiency over the reflector
  surface
• The gain and pattern are also effected by the
  reasons mentioned above

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Theoretical background - Antenna arrays (1)
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Theoretical background - Antenna arrays (2)

• Definition assembly of number radiating elements
  in geometrical Electrical configuration
• Attributes
• High directivity achieved without enlarging the
  elements dimensions
• Gain direction of the main lobe determine by
  configuration- distance phase between elements
  and their amount
• Grating lobes achieved by using large number of
  elements
• Maximum radiation point in space of the array
  controlled by the distance the phase difference
  between the elements.

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Concept Description (1)
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Concept Description (2)
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Concept description (3)

• Deformations mainly orthogonal to the antenna
  plane P
• Perfect self compensation (no difference in the
  wave plane path).
• Not the natural position for a satellite ground
  mission

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Concept description (4)
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Concept description (5)

• In natural geometry the atitude
  of the prism can have
• roll, pitch and yaw

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Concept description (6)-Self compensation

• Illuminating satellite prism same orbit,
  distance of 5-100 Km
• Self compensation
• Mission frequency Illuminator frequency
• .
• Illuminator 1 transmit 2 signals. Data
  reference tone Fe
• Mission data carrier frequency is f
• Illuminator data carrier frequency fF FFiFe
• A cone around the prism mark a track (self
  compensated) on the ground
• Is a mission bounded to move only along this cone
  ?

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Concept description (7)- Mission field of view

• Ground mission illuminator moves the geometry
  changes by
• Phase compensation residue standard antenna
  but ,with a relaxation factor

• For
  ,flatness is relaxed from to (12 cm
  for L band ,35 cm for L band antennas)
• For
  mission FOV can reach
• However , Fi increases sensitivity to prism
  deviation in attitude
• It is possible to measure prism deformation at
  order electronically correct it with phase
  shifters

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Concept Implementation

• Antenna folding (inside the satellite) until it
  reaches the mission area, and then be extracted.
• RF cable No need
• Beam steering achieved with a phase ramp in case
  of narrow band delay lines in case of wide band
• Relative position between the satellites
  measured (optics or interferometer or DGPS) in
  order to electronically correct attitude
  deviation.
• Impact of frequency deviation (Doppler etc.)
  negligible for small F use of pure delay lines.
  

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Concept Implementation
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Concept Implementation (2)

• Prism side composed of an array of elementary
  tiles
• Elementary tiles architecture
• Dual Band Active patch antenna (Fe and Ff)
• TR switch ability to separate the Fe signal
  (diplexer/part of the active antenna)
• Mixers
• Delay line
• Beam forming network
• Active patch antenna (f)

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Concept Implementation (3) link budget

• Prism side
• Rear (illuminator side) sampling 7 times the
  wave length
• Link budget for rear side
• Tile transmit signal s noise n p tiles -gt
  illuminator receives p times signal s p
  uncorrelated n ,the receiver adds n noise.
• Max n impact 0.5 dB verify pn/ngt8.
• Illuminator antenna with effective aperture to
  1m2 300Mhz bandwidth at a distance of 100 Km
• Transmit loss of 8dB in the rear link each tile
  has to transmit
• with 10 tiles SNR of 25dB each tile has to
  transmit 0.5W

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Architecture Examples
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Possible Applications

• Geostationary communications (Fi0) relaxation
  factor 1/10 with 10? FOV -45? inclining with
  respect to nadir (Z axis)
• Low orbit side looking communication/ radar
  roll 45? FOV of 35?-55?
• Vertical antenna/SAIL type satellite for radar
  or telecom low orbit
• Yaw of 55?

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Possible Applications (2)

• Geostationary multi beam satcom 400 L Band beams
  of 400km footprint (1.5/1.6 Ghz)
• Require 0.6 degrees beam width (effective
  aperture of 20M)
• 16 beam pattern meshing of
• Pattern repeated 25 times
• 16 illuminators each transmit 25 (j1..25)
  distinct different channel (fjF)

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Conclusions!

• RF prism new system approach (rather then new
  technology)
• Large aperture antenna deployed into space
• Draw Backs
• Active Antenna require complex development
  power consumption.
• Effective Aperture reduction due to angle of the
  antenna plane
• Additional satellite need-gt additional cost

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Further Research

• Beam model of wave propagation yet to be
  verified (full wave analysis, simulations)
• Multi Illuminators linearity of the systems- to
  be examined considering the frequency
  translations active antennas
• Large Bodies In Space difficulties, satellite
  out of balance (change in moments)

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