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IEIIT ­ Istituto di Elettronica e di Ingegneria dell'Informazione e delle Telecomunicazioni c/o Politecnico di Torino, Italy

Antenna Design Study for AAlo 70-450 MHz
G. Virone, R. Tascone, O. A. Peverini, G. Addamo, F. Perini*, J. Monari*, M. Schiaffino*
*Istituto di Radio Astronomia Istituto Nazionale di Astro Fisica

Applied Electromagnetics Group

AAVP 2010, Cambridge


National Research Council Institute of Electronics and Information and Communication Engineering

· 134 people · 5 cities: Turin, Milan, Bologna, Genoa, Pisa · Information and Communication Technology ­ Computer and Systems Engineering ­ Applied Electromagnetics ­ Telecommunications ­ Electronics
Applied Electromagnetics Group AAVP 2010, Cambridge


Recent Activities
- Architectures, antennas, waveguide components, VCSELs, composite radomes Reflection coefficient - Analysis Techniques (MOR) - Design/Synthesis Methods - Measurement techniques
0 -10 -20 Pre-Optimi zation Post-Optimizati on Measurement [dB] S -40 -50
11

-30

66 %
12 14 16 18 Frequency [GHz] 20 22

-60 10

G. Addamo, et al, A Ku-K Dual-Band Compact Circular Corrugated Horn for Satellite Communications. IEEE AWPL, Vol. 8, pp. 1418 - 1421, 2009 Applied Electromagnetics Group AAVP 2010, Cambridge


AAlo Specifications
· Frequency band : 70 ­ 450 MHz · Dual linear polarization antenna · Maximum cross pol. at zenith< -20 dB · Low losses metal-only configurations

· Sparse array condition (no mutual coupling is considered) · Sky coverage ±45° (±60° ) in both planes
Applied Electromagnetics Group AAVP 2010, Cambridge


Single Array Element approach
Maximize

^ Aeff (r )
an

^ Aeff (r )

Tsys d Tsy

^ r

Sky-coverage

s pertain to the single array element

Theoretical limit for the maximum gain
Optimum radiation pattern

GM ^ G (r ) = 0
±45° 8.3 (7.5)

ax

^ r Sky -cov. elsewhere
±60° 6 (5.4)

Sky Coverage [Deg]

GMa

x

[dB]

Applied Electromagnetics Group

AAVP 2010, Cambridge


Matching considerations
Signal-to-noise ratio at the LNA input

Aeff (1 - TA (1 -
K2

K2

)
NA

) + TL
K

Kurokawa Power Reflection Coefficient

Z = Z

LNA LNA

-Z +Z

* An t An t

Proper matching is important when

TLNA

is not negligible with respect to

T

A

Applied Electromagnetics Group

AAVP 2010, Cambridge


Dual polarization Vivaldi
Maximum size = 1.1 m Possible gridded version Unbalanced excitation No cross-pol at zenith

Applied Electromagnetics Group

AAVP 2010, Cambridge


Reflection coefficient
Referenc e Impedanc e : 75 Ohm 0 -5 Ref lec tion Coeffic ient (dB)

-10

-15

-20

-25

-30

0.1

0.2

0. 3

0. 4 0.5 0.6 Frequenc y (GHz )

0.7

0.8

0. 9

Applied Electromagnetics Group

AAVP 2010, Cambridge


H-plane Radiation Pattern
H-plane radiat ion patt ern (Phi= 0 Deg) 10 70 MHz 260 MHz 450 MHz 5

0 Direc t iv it y (dB)

-5

-10

-15

-20

0

20

40

60

80 100 Theta (Deg)

120

140

160

180

Applied Electromagnetics Group

AAVP 2010, Cambridge


E-plane Radiation Pattern
E-plane radiation pat tern (Phi= 90 Deg) 10 70 MHz 260 MHz 450 MHz 5

0 Direc tiv ity (dB)

-5

-10

-15

-20

0

20

40

60

80 100 Theta (Deg)

120

140

160

180

Applied Electromagnetics Group

AAVP 2010, Cambridge


Realized Gain at zenith
8

Realiz ed Gain (dB)

dP( ) GR ( ) = dic Pn 4 r 2
Matching is accounted for

6 4 2 0 -2 -4 -6

dP( ) G ( ) = inc d r P -P 4 r 2

efl

-8

0. 1

0. 2

0. 3

0. 4 0. 5 0. 6 Frequenc y (GHz )

0. 7

0. 8

0. 9

Applied Electromagnetics Group

AAVP 2010, Cambridge


Effect of the antenna dimension (1)
10 8 6 4 2 0 -2 -4 -6 -8 W =1 m W =2 m

Larger antenna

Realiz ed Gain (dB)

Smaller antenna

0. 1

0.2

0.3

0. 4 0.5 0.6 Frequenc y (GHz )

0. 7

0.8

0.9

Applied Electromagnetics Group

AAVP 2010, Cambridge


Effect of the antenna dimension (2)
Referenc e Impedanc e : 75 Ohm 0 W =1 m W =2 m -5 Ref lec tion Coef fic ient (dB)

-10

-15

-20

-25

-30

0. 1

0.2

0.3

0. 4 0.5 0.6 Frequenc y (GHz )

0. 7

0.8

0.9

Applied Electromagnetics Group

AAVP 2010, Cambridge


Back lobe reduction
H-plane radiat ion pattern (P hi= 0 Deg) @120 MHz 10 W =1 m W =2 m 5

0 Direc t iv it y (dB)

-5

-10

-15

-20

0

20

40

60

80 100 Theta (Deg)

120

140

160

180

Applied Electromagnetics Group

AAVP 2010, Cambridge


Effect of a soil ground plane
10 8 6 4 2 0 -2 -4 -6 -8 No ground Finit e Dielec tric Ground Diamet er= 3*W ant Dept h= 2*Lant Finit e Dielec tic Ground Diameter= 4*W ant Depth= 3*Lant

R=6 =0.01 S/m

Realiz ed Gain (dB)

0. 1

0.2

0.3

0. 4 0.5 0.6 Frequenc y (GHz )

0. 7

0.8

0.9

Applied Electromagnetics Group

AAVP 2010, Cambridge


Effect of a soil ground plane (2)
Finit e Dielec tic Ground Diameter= 4*W ant1 Dept h= 3*Lant1 10 8 6 4 2 0 -2 W 1= 1 m W 2= 2 m

Larger antenna

Realiz ed Gain (dB)

Smaller antenna
-4 -6 -8

0. 1

0.2

0.3

0. 4 0.5 0.6 Frequenc y (GHz )

0. 7

0.8

0.9

Applied Electromagnetics Group

AAVP 2010, Cambridge


Conclusion & Future Work
· The Dual Pol Vivaldi is a promising structure · Optimization of the profile · Gridded Version for AAlo
Giuseppe Virone, RИmi Sarkis, Christophe Craeye, Giuseppe Addamo and Oscar A. Peverini, "Gridded Vivaldi Antenna Feed System for the Northern Cross Radio Telescope", IEEE-AP Special Issue on RadioAstronomy

· Experimental validation
Applied Electromagnetics Group AAVP 2010, Cambridge


Applied Electromagnetics Group

AAVP 2010, Cambridge


Effect of a metallic ground plane
10 8 6 4 2 0 -2 -4 -6 -8

Realiz ed Gain (dB)

No ground Finite PEC Ground 1/ 4 Finite PEC Ground 1/ 2

0. 1

0.2

0.3

0. 4 0.5 0.6 Frequenc y (GHz )

0. 7

0.8

0.9

Applied Electromagnetics Group

AAVP 2010, Cambridge


Finite Metallic Ground Plane
H-plane radiation pat tern (Phi= 0 Deg) @ 70 MHz 10 5

0 Direc t iv it y (dB)

-5 No ground -10 PEC 1/4 PEC 1/2 -15

-20

0

20

40

60

80 100 Theta (Deg)

120

140

160

180

Applied Electromagnetics Group

AAVP 2010, Cambridge