Fourth Year Final Project - BGU HF Electromagnetic Vector Sensor

1
Fourth Year Final Project - BGU HF
Electromagnetic Vector Sensor

• Students
• Roy Nevo, Yiftach Barash
• Advisors
• Mr. Benny Almog
• Prof. Reuven Shavit
• 17.5.2011

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Challenges and Motivation

• Electromagnetic direction finding (DF) is of high
  priority, both for civilian and military needs.
• In the High-Frequency (HF) range (3-30MHz) the
  common passive DF methods require very large
  aperture (tens of meters).
• Thus, HF DF system is bulky to carry and to
  set-up.
• Small aperture antenna array and elements (in
  terms of wavelength) that perform DF is required.

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Project Goals

• Main Goal
• Using the Poynting theorem to produce a small
  antenna for
• HF-DF applications
• Objectives
• Wideband in the HF region
• Simultaneous azimuth
• and elevation finding
• RMS error lt 2
• Production of the antenna
• Test environment for the HF range The TEM Cell

?80 f157
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Project Final Result

• The sensor basic element and its feeding
  circuitry were simulated and produced
• TEM-cell test environment was also simulated and
  produced
• The antenna was measured inside the TEM-cell and
  the total RMS error of the azimuth and elevation
  estimation was lt 2

Simulation -Total Error RMS 1.43
Measurements - Total Error RMS 1.98
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Theoretical BackgroundThe Poynting Theorem

• Propagating EM plane wave
• in free space
• E-field - H-field - Propagation (Poynting
  vector).
• The Poynting Theorem
• From the Cartesian elements of the fields, the
  propagation direction can be extracted

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Theoretical Background Electric and Magnetic
Dipoles

• Electric dipole on the Z axis
• Response related to Ez

• Magnetic dipole on the Z axis
• Response related to Hz

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Simulated Elements

• Small Electric Dipole
• Small Loop
• Magnetic Dipole
• Combined element
• Slotted Dipole
• With less coupling
• and thus, possibly, higher SNR

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Dipoles Simulation

• Electric and magnetic dipoles far field
  (incident wave response).

Electric dipole far field radiation (E?)
Rectangular loop far field radiation (Ef)
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Dipoles Simulation

• Slotted Dipole far field (incident wave
  response).

Electric dipole far field radiation (E?)
Slot far field radiation (Ef)
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Test Environment The TEM cell

• The TEM-cell was matched to have 200O impedance
• The Electric field orientation in the center is
  well defined

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Combined Simulation DF analysis

• Simulation results 6 dipoles in the TEM CELL

? 7.12E-06 Ex
? 5.02E-09 Ey
? 4.63E-04 Ez
? 2.35E-06 Hx
? 5.19E-02 Hy
? 1.03E-07 Hz
2.39E-05 Sx
1.09E-09 Sy
1.45E-07 Sz
Angle Expected Simulation result
Phi 0 0.0023
Theta 0 0.34
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Orientation Index

• Polarization0
• Theta0
• Phi0

• Polarization0
• Theta30
• Phi0

• Polarization0
• Theta0
• Phi30

• Polarization30
• Theta0
• Phi0

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DF Results and Noise Analysis
Error in RMS Phi Theta Abs
Dipole and Loop 2.0275 0.9701 2.2476
Slotted Dipole 1.3266 0.5481 1.4353

• The slotted dipole show better DF result in
  simulation
• For good performance, with no signal processing
  operations, the signal must be larger than the
  noise in at least 20dB.

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The TEM-cell

• The TEM-cell was produced from wood (EM
  transparent) and two parallel metal net (EM
  plate)
• From S parameters measurements, the TEM-cell is
  well matched and perform as parallel plate
  transmission line

Output/ Termination
Input
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Testing System Layout

• The antenna is placed on special holders with
  different angels in the TEM-cell.
• The TEM-cell is connected to port 1, the
  antenna to port 2 of the ENA and S21 is measured.

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Sensor Element Measurement Results

• The elements directional response is as expected
  !
• In most of the HF range, the signal response in
  the TEM is larger than the noise in more than 30dB

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Sensor Element Measurement Results

• In the HF range the antenna gain is very small
• small antenna-large bandwidth limitation
• The DF result on arbitrary angle show good
  performance up to 20MHz (The magnetic dipole
  upper limitation)

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Measurements Results and Comparison to Simulation
Error RMS Error - ? Error - f ? ? f f ? ß a
0.92 0.98 0.86 0 0 0 0 0 0 0
1.43 0.8 1.86 58 58 -16 -16 45 45 45
0.75 0.48 0.94 47 47 -58 -58 60 45 30
3.51 3 3.95 4 4 12 12 30 60 30
1.98 1.98 Total Error-RMS Total Error-RMS Total Error-RMS Total Error-RMS
        1.43 1.43 Simulation -Total Error-RMS Simulation -Total Error-RMS Simulation -Total Error-RMS Simulation -Total Error-RMS
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Conclusion and Future Steps

• A novel HF DF antenna was developed and produced
• The antenna is very small in terms of wavelength
  and thus highly mobile
• The DF RMS error lt 2 as was initially specified
• Continuous measurements and signal processing
  algorithm (MUSIC) will be applied in order to
  further reduce the RMS error

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References

• 1 C. Balanis, Antenna theory Wiley New York,
  1997.
• 2 C. Balanis, Modern Antenna Handbook Wiley
  New York, 2008.
• 3 A. Nehorai and E. Paldi, "Vector sensor
  processing for electromagnetic source
  localization," in Signals, Systems and
  computers, 1991.
• 4 C. E. Smith and R. A. Fouty, Circular
  Polarization in F-M Broadcasting, Electronics,
  vol. 21 (September 1948) 103 107. Application
  of the slotted cylinder for a circularly
  polarized omnidirectional antenna.

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Thank You For Your AttentionQuestions ???
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The slotted dipole

• Simulation results current density

Electric dipole ports generator - J A/m
Slot ports generator - J mA/m
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Project Methodology
Production and Measurements
Simulation
Analysis
Electric and magnetic dipoles basic simulation in
different realizations
Production of the TEM-cell and S-parameters
measurements for match evaluation
DF calculation and comparison with the simulation
results
Detailed simulation of selected realization
including feed
Production of one element of the antenna
electric and magnetic dipole
Calculation and simulation of the TEM-cell for
match evaluation
Measurement of the electric and magnetic dipole
response in the TEM-cell in different orientation
Simulation of the dipoles in the cell and DF
calculations
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Project Methodology
Production and Measurements
Simulation
Analysis
DF calculation
Electric and magnetic dipoles basic simulation
Production of the TEM-cell and S-parameters
measurements
Detailed simulation including feed
Production of electric and magnetic dipole
Calculation and simulation - TEM-cell
Measurement of the electric and magnetic dipole
in the TEM-cell
Simulation and DF calculation