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Space-Based VIRTUAL APERTURE ANTENNAS

A technology that enhances the effective electrical aperture of antennas, supporting both surface and leaky waves.

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Space-Based VIRTUAL APERTURE ANTENNAS

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  1. L F inc Space-Based VIRTUAL APERTURE ANTENNAS ULTRA-HIGH GAIN

  2. L F inc Space-Based VIRTUAL APERTURE ANTENNAS Virtual Aperture ~ 100:1 “An antenna whose effective electrical aperture greatly exceeds it’s real physical aperture”

  3. L F inc SURFACE WAVES “A surface wave is an electromagnetic wave that propagates along the interface between two media having different velocities of propagation.”

  4. L F inc EXAMPLE STRUCTURES Each of these structures can support both surface and leaky waves

  5. a a a L F inc Antenna Theory of Operation Dielectric Waveguide (fiber optic) No Radiation Launcher near rod center, a>>l Continuous Radiation Along Length Leaky-Wave Antenna (Polyrod Antenna) Complex launcher within rod, a ~ l This is a tremendous technological advance- it is not well understood in the literature. LFinc Surface Wave Antenna End-Fire Radiation Launcher outside of rod, a ~ l/2

  6. L F inc Almost every error of conceptualization of this antenna occurs by confusing it with a leaky wave

  7. L F inc

  8. L F High surface wave launching efficiency- inc • Good ratio of usable to unusable power Efficient transition from tight to loose binding- • Reduces loss of usable power • Maintains good field purity In space, we can support a very small rod radius- • Provides very large virtual aperture Essential Issues of the Antenna System The elements of success

  9. L F inc Antenna Concept Launcher Radiation LINES OF CONSTANT AMPLITUDE LAUNCHER TAPERED DIELECTRIC ROD LINES OF CONSTANT PHASE Launcher near field Well defined surface wave

  10. L F inc The Physics of the LFinc Antenna The Mathematics of Surface Waves When a source exists equations (1) through (5) must include this source. Consider a magnetic ring source as shown. This can be represented mathematically by, (6) b where d is a Dirac delta function, and a sinusoidal current variation is assumed in f: (eq (1) becomes) e0 (7) er y resulting in a vector wave equation given by (eq (4) becomes), 1 2 3 (8) a r Expanding Eq (8), and examining the z component yields, magnetic ring source f (9) x (10) Solutions are sought that have the following functional dependence: (11) (14) (12) (15) (13) (16)

  11. This branch cut represents direct radiation away from the magnetic ring source L F V V inc V G R G V V V x V x V V V -R +R Contour of integration in the z-plane This pole represents the surface wave propagation away from the magnetic ring source The Physics of the LFinc Antenna The Mathematics of Surface Waves

  12. 0.8 b/a=1.0 1.1 0.7 1.2 1.4 0.6 L 1.6 F 0.5 1.8 inc 2.0 0.4 2.5 3.0 0.3 4.0 0.2 0.1 0.50 0.30 0.40 ~82% e1/e0 = 2.56 Launching Efficiency h 2a/l0

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