Unclassified 1 - REF 18.6.2014 This document contains proprietary information of ELTA Systems Ltd and may not be reproduced, copied, disclosed or utilized.

Unclassified 1-REF

18.6.2014

This document contains proprietary information of ELTA Systems Ltd and may not be reproduced, copied, disclosed or utilized in any way in whole or in part, without the prior written consent of ELTA Systems Ltd

ELTA Systems

Department of Electrical and Computer Engineering - BGU

VHF vector sensorVHF vector sensorStudents: Musicant Amir

Advisors:Prof. Reuven ShavitMr. Benny Almog Mr. Nadav Oxenfeld

E

H

S

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This document contains proprietary information of ELTA Systems Ltd and may not be reproduced, copied, disclosed or utilized in any way in whole or in part, without the prior written consent of ELTA Systems Ltd

SIGINT, EW & Communication Division

Project goalsProject goals

Planning an electromagnetic small antenna for the evaluation of the angle of arrival (AOA).

Frequency band: 30-90 MHz.

Maximum RMS error less than 5º.

Efficiency requirement:

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Theoretical backgroundTheoretical background

Poynting theorem

The direction of is the direction of the propagating wave from the transmitter.

The small electric and magnetic dipoleProjection

on the dipole axes.

Dipole dimensions must

be less than 0.1λ(=0.3m).

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Vector sensorVector sensor

6 orthogonal electric and magnetic dipolesMeasure the Cartesian field components.

Collocated six antennas.

Orthogonal structure.

The magnetic dipole is a small loop.

The electric dipole is a short wire.

The dipoles axes

are as shown here.

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The magnetic dipole constructionThe magnetic dipole construction

Challenges:Trade off between efficiency and resonance.

Size limitations (Airborne).

- Efficiency required- Efficiency upper

bound

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The magnetic dipole constructionThe magnetic dipole construction

The multi-wire helixIn the single wire helix additional turns increase efficiency and decrease band width.

The multi-wire approach increases efficiency without decreasing the band width.

Efficiency converges to upper practical bound.

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The magnetic dipole constructionThe magnetic dipole construction

The electric dipole.

Performance.

- Required efficiency- Electric dipole

efficiency- Magnetic dipole

efficiency

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The magnetic dipole constructionThe magnetic dipole construction

One turn loop of wide strip.Effective volume theory.

Performance.

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The magnetic dipole constructionThe magnetic dipole construction

Ferrite core helix.Increase radiation resistance by factor.

Adds core losses which reduces efficiency.

Adds weight.

- 10 cm diameter multi-wire helix.

- 5 cm diameter, 3 ferrites cores helix with 3 turns and 8 wires.

- 5 cm diameter, 3 ferrites cores helix with 4 turns and 16 wires.

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The magnetic dipole constructionThe magnetic dipole construction

Kanda’s loop

Thus,

More compact solution.

Enables to increase loop diameter.

Less coupling between elements.

Increase magnetic dipole efficiency.

Decrease electric dipole efficiency.

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Kanda’s loopKanda’s loop

Efficiency results

Electric dipole performance deteriorates by 3 dB.

Magnetic dipole performance improved by 7 dB.

20 30 40 50 60 70 80 90 100-55

-50

-45

-40

-35

-30

-25

-20

X: 84Y: -27.96

Frequency [MHz]

Eff

icie

ncy [

dB

]

Electric dipole comparison

X: 32Y: -42.91

X: 32Y: -45.51

20 30 40 50 60 70 80 90 100-55

-50

-45

-40

-35

-30

-25

-20

X: 32Y: -37.15

X: 32Y: -43.89

X: 88Y: -26.91

X: 88Y: -31.95

Magnetic dipole comparison

Frequency [MHz]

Eff

icie

ncy [

dB

]

- Multi wire- kanda’s loop

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Experiment set upExperiment set up

TEM cell emulates the far field.

The orientation jig enables testing the antenna in all orientations.

The two ports was measured by a network analyzer.

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Experiment resultsExperiment results

Gain results - Simulation- Measurement

Electric dipole Magnetic dipole

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Experiment resultsExperiment results

Pattern results

0 20 40 60 80 1000

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1Pattern of the Electric element, theta cut

Theta[degrees]

U

0 20 40 60 80 1000.97

0.98

0.99

1

1.01

1.02

1.03

1.04Pattern of the Electric element, phi cut

Phi[degrees]

U

0 20 40 60 80 1000

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1Pattern of the Magnetic element, theta cut

Theta[degrees]

U

0 20 40 60 80 1000.98

1

1.02

1.04

1.06

1.08

1.1

1.12Pattern of the magnetic element, phi cut

Phi[degrees]

U

simlab

sin2 (theta)

sim

lab1

simlab

sin2 (theta)

sim

lab1

- Simulation- Measurement

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AOA estimation errorAOA estimation error

3D simulation was preformed.

The error calculation:

E

H

S𝜃

∅

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AOA estimation errorAOA estimation error

Error results.

phi[deg]

theta

[deg]

Average error of AOA estimation with spline interpolation

0 50 100 150

20

40

60

80

100

120

140

1600.5

1

1.5

2

2.5

3

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Theoretical AOA estimation errorTheoretical AOA estimation error

Frequency dependent error (simulation)

20 30 40 50 60 70 80 90 1000

0.5

1

1.5

2

2.5

3Average error as function of frequency

Frequency[Mhz]

Avera

ge e

rror[

deg]

error

2 degrees

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summerysummery

The increase in loop’s area is the main contributor to the efficiency improvement of the magnetic dipole.

Kanda’s loop is a good candidate for the vector sensor antenna.

Good AOA estimation results was achieved in simulation.

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Future workFuture work

Constructing an aerodynamic structure for the antenna.

Test the influence of a platform on the antenna performance.

Preforming field experiment and calibration.

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ReferencesReferences

A. Nehorai and E. Paldi, "Vector sensor processing for electromagnetic source localization" in Signals, Systems and Computers, 1991. 1991 Conference Record of the Twenty-Fifth Asilomar Conference on, 1991, pp. 566-572 vol.1.

ITU R. P-372.10(2009). Radio noise. P series. Radio wave propagation.

Volakis, John L. (2010). Small antennas miniaturization techniques & applications. U.S: The McGraw-Hill companies.

M. Kanda, "An elctromagnetic near-field sensor for simultaneous electric and magnetic-field measurements" IEEE transactions on elctromagnetic compatibility. VOL. EMC-26,N0.3 august 1984.

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questions

?

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Movie linkMovie link

https://www.youtube.com/watch?v=EZ4noiEapSA&feature=youtu.be