Transcript Document
Fourth Year Final Project - BGU
HF Electromagnetic
Vector Sensor
Students:
Roy Nevo, Yiftach Barash
Advisors:
Mr. Benny Almog
Prof. Reuven Shavit
E
H
θ=80˚
S
φ=157˚
17.5.2011
Department of Electrical and
1
Computer Engineering - BGU
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.
2
Project Goals
Main Goal:
Using the Poynting theorem to produce a small antenna for
HF-DF applications
E
Objectives:
Wideband in the HF region
H
S
Simultaneous azimuth
and elevation finding
RMS error < 2˚
θ=80˚
Production of the antenna
φ=157˚
Test environment for the HF range – The TEM Cell
3
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 < 2˚
Simulation 1.43
Total Error RMS
Measurements - 1.98
Total Error RMS
4
Theoretical Background
The Poynting Theorem
Propagating EM plane wave
in free space:
E-field ┴ H-field ┴ Propagation (Poynting vector).
The Poynting Theorem
1
S EH
2
From the Cartesian elements of the fields, the propagation
direction can be extracted
5
Theoretical Background
Electric and Magnetic Dipoles
Z
Electric dipole on the Z axis
Response related to Ez
E
Y
H
Magnetic dipole on the Z axis
Response related to Hz
Ez
H E
Y
X
2
ka I 0e jkr
zˆ k I
4r
Z
X
1 z
S x E y H z E z H y k1k 2 I y _ dipole I z_ loop I z _ dipole I y _ loop
S y E z H x E x H z ...
S z E x H y E y H x ...
Sy
at an
, at an
Sx
Sz
S x 6 S y
2
2
Simulated Elements
Small Electric Dipole
Small Loop –
Magnetic Dipole
Combined element –
Slotted Dipole
With less coupling
and thus, possibly, higher SNR
7
Dipoles Simulation
Electric and magnetic dipoles – far field (incident
wave response).
Electric dipole far field radiation
(Eθ)
Rectangular loop far
field radiation (Eφ)
8
Dipoles Simulation
Slotted Dipole – far field (incident wave response).
Electric dipole far field radiation
(Eθ)
Slot far field radiation
(Eφ)
9
Test Environment – The TEM cell
The TEM-cell was matched
Ez [V/m]
to have 200Ω impedance
The Electric field orientation
in the center is well defined
Ex [mV/m]
Ey [mV/m]
10
Combined Simulation – DF analysis
Simulation results – 6 dipoles in the TEM CELL
Sx
Ez
Hy
|Ex|
7.12E-06
|Ey|
5.02E-09
|Ez|
4.63E-04
|Hx|
2.35E-06
|Hy|
5.19E-02
|Hz|
1.03E-07
|Sx|
2.39E-05
|Sy|
1.09E-09
|Sz|
1.45E-07
H
z
E
S
Z
E
Y
y
X
x
1 Expected
S EH
Phi
0
2
Angle
H
Theta
Simulation
result
0.0023
0
0.34
11
Orientation Index
Polarization=30˚
Polarization=0
Theta=0
Theta=30˚
Phi=30˚
Phi=0
12
DF Results and Noise Analysis
The slotted dipole show
better DF result in
simulation
Error in RMS
Phi
Theta
Abs
Dipole and Loop
2.0275
0.9701
2.2476
Slotted Dipole
1.3266
0.5481
1.4353
40
For good performance,
RMSE
with no signal processing
operations, the signal
must be larger than the
noise in at least 20dB.
30
20
10
0
-20
0
20
40
60
Currents SNR [dB]
80
13
100
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
0
S11 amplitude
S21 amplitude
[dB]
-10
-20
-30
0
5
10
15
20
Frequency [MHz]
25
30
14
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
Ex amplitude
Ey amplitude
Ez amplitude
-20
directional response
is as expected !
[dB]
-40
-60
In most of the HF
range, the signal
response in the
TEM is larger than
the noise in more
than 30dB
-80
0
10
15
20
10
15
Frequency [MHz]
20
25
30
25
30
Hx amplitude
Hy amplitude
Hz amplitude
-20
-40
[dB]
5
-60
-80
-100
0
5
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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)
=30 =45 =60
-40
10
Error in
Error [degree]
Gain [dBi]
-50
-60
-70
Electric dipole Gain
Magnetic dipole Gain
-80
-90
0
5
10
15
20
Frequency [MHz]
25
30
Error in
5
0
-5
0
5
10
15
20
Frequency [MHz] 17
25
30
Measurements Results and Comparison
to Simulation
α
β
γ
φ
θ
Error - φ
Error - θ
Error – RMS
0
0
0
0
0
0.86
0.98
0.92
45
45
45
-16
58
1.86
0.8
1.43
30
45
60
-58
47
0.94
0.48
0.75
30
60
30
12
4
3.95
3
3.51
Total Error-RMS
1.98
Simulation -Total Error-RMS
1.43
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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 < 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 Attention
Questions ???
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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
Simulation
Production and
Measurements
Electric and magnetic
dipoles basic simulation
Production of the TEMcell 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
Analysis
DF calculation
Simulation and DF
calculation
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