ElectroScience Laboratory 1 DESIGN OF MUTUALLY TRANSPARENT ANTENNA ARRAYS JOHDPUR FEB. 28-29,2008 AND BANGALORE MAR. 3-4, 2008 Dr. Eric K. Walton The

1

ElectroScience Laboratory

DESIGN OF MUTUALLY TRANSPARENT ANTENNA

ARRAYS

JOHDPUR FEB. 28-29,2008 AND

BANGALORE MAR. 3-4, 2008

Dr. Eric K. WaltonThe Ohio State University

ElectroScience Lab.

[email protected] 614 292 5051


2BASIC CONCEPT OF THE FSS ARRAY ANTENNA

CLUSTER

ARRAY 2

ARRAY 3

ARRAY 1

BEAM 3

BEAM 1 BEAM 2

MUTUALLY TRANSPARENT ANTENNA ARRAYS MOUNTED INSIDE A RADOME

MECHANICALLY STEERED BEAMS

RADOME


3

BASIC ARRAY CONCEPT

RADIATING ELEMENTSPRINTED ON MYLAR

FSS GROUND PLANEPRINTED ON MYLAR

FSS TRANSMISSION LINES PRINTED ON

DUROID

EACH OUTER ARRAY ANTENNA IS TRANSPARENT TO THE INNER ARRAYS

EACH TRANSPARENT ANTENNA PANEL:

STYROFOAMDIELECTRIC


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MUTUALLY TRANSPARENT FSS ARRAY ANTENNAS


5

Center part of layout; view from top

Red = transmission linesYellow = slots in foamOrange = holes in foam/MylarGreen = FSS pattern on Mylar(ant. Elements not shown)

This layout is only so that the basic repeating pattern can be understood.


6

RF Transparent Array Antenna for Dense Array Cluster

The transmission line array was perhaps the most complex part of the entire system. (See presentation by Eugene Lee)

Proportional power directional couplers

Main trunk line

Branch lines

Rotatable feed stubs


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Radiating CP dipoles

FSS Ground Plane

Transmission Line

TRANSMISSION LINE LOCATION

GAP “D”


8

THE TRANSMISSION LINE FEED SYSTEM


9TRANSMISSION LINE FEED SYSTEM

Single branch tap


10

S band transmission line distribution at 2230 MHz


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12

• Length of side = 0.354λ = 62.58 mm

• Size of break = 0.016λ = 2.82 mm

• Size of connector = 8 mm

• Resonant Frequency = 1697MHz

• Input Impedance = 61.914 + j 0.080773 Ω

• Max gain = 3.888 dBi

A DUAL RHOMBIC LOOP ANTENNA FOR CIRCULAR POLARISATIONH. Morishita , T. Iizuka, K. Hirasawa and T.Nagao

Antennas and Propagation, 4-7 April 1995Conference Publication No. 407,O IEE 1995.


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Comparison of Element Designs

• Element Radius = 0.45λ (0.079m)

• Single Loop Circumference = 1.33λ (0.236m)

• Zin @ 1697 MHz = 90.691 – j 2.039 Ω



• Zin @ 1697 MHz = 90.959 – j 2.387

Cut Corners Concave Corners



• Zin @ 1697 MHz = 61.268 – j 8.959 Ω

Square Corners(original element)


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S-band Arrays

• Single element side length and break position was optimized for peak gain at resonance (see appended slides)

• 14x14 array simulated over ‘+x+x+’ FSS ground planes of different sizes (results on following three slides)

x

y

z

1 m

Figure 2: Sample FSS Configuration

Figure 1: Sample S-band Element (side length, s =

0.34λ2230MHz; break position = 2/3)

s


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Flat loop antenna


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Abused (cold) grad students: Eugene Lee (PHD)

And Ryan Pavlovicz (Senior – soon to be grad student)

TESTING THE FLAT LOOP ANTENNA


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FSS GROUND PLANE PRINTED ON MYLAR

RADIATING ELEMENTS AND FSS GROUND PLANE ARE MADE OF COPPER OR SILVER PRINTED ON MYLAR

DIELECTRIC SUBSTRATE IS SIMPLY A PANEL OF STYROFOAM(THE MYLAR LAYERS GIVE IT STRENGTH AND RIGIDITY)

THE TRANSMISSION LINE STRUCTURE IS TWIN LINES PRINTED ON STABLE DIELECTRIC


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FSS


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Array with FSS


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22

FULL SYSTEM MODELING

EXAMPLE; WIRE GRID MODEL OF L-BAND ARRAY BLOCKING S-BAND ARRAY

RADIATING ELEMENTS;FSS LAYER;

TRANSMISSION LINE SYSTEM


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1 m

S-band Octagonal Array

• 156 Elements

• Input impedance ~ 103.7 + j17.6Ω

• Boresite gain = 31.9 dBiC

• 162 x 152 FSS ground plane

MODELING RESULTS


24S-Band Boresight gain

vs. frequency for individual quadrants


25CR BLOCKAGEExperimental Setup

Range center line

84”

ANTENNA ARRAY PANELS(SET UP FOR TRANSMISSIVITY TESTING)

Eugene’sSlide

~(12’ x 6’ x 5”)Support

Legs

Walton

(not to scale)

Foam Support columns

ROTATE

SLIDE


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COMPACT RANGE BLOCKAGE TESTING

ARRAYS

FOAM SUPPORTS

HANDSOMEGRAD

STUDENT


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ANALYSIS OF EXPERIMENTAL TESTING

S band array at boresight vs. L band array blockage

GAIN (DBIC) VS. FREQ. (MHZ)

Percent blockage results


28S band array patterns @ 2170 MHz

for different blockage %

S band blocked by L-band arrayNONE; 0%; 25%; 50%; 75%; 100%

GA

IN (

DB

IC)

-40

-3

0 -

20

-10

0

1

0

20

-80 -60 -40 -20 0 20 40 60 80AZIMUTH (DEG)


29S band array patterns @ 2170 MHzfor different occlusion % [zoom]G

AIN

(D

BIC

)

-40

-3

0 -

20

-10

0

1

0

20

-25 -20 -15 -10 -5 0 5 10 15 20 25AZIMUTH (DEG)



30S band array patterns @ 2170 MHzfor different occlusion % [zoom 2x]

S band blocked by L-band arrayNO; EDGE; 25%; 50%; 75%; 100%

GA

IN (

DB

IC)

8

10

1

2

14

16

18

2

0

-5 -4 -3 -3 -1 0 1 2 3 4 5AZIMUTH (DEG)


50% blockage

100 % blockage

No blockage


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Full Array gain max

Freq Boresight Gain

HPBW (deg)

HPBW gain (50% eff)

Theoretical 2230 MHz 32.06 dBiC 4.2 30.14

Outdoor 2020 MHz 22.05 dBiL / 22.23 dBiL

4 30.56

Anechoic Chamber

2170 MHz 22.12 dBiC 5 28.62

Synthesized from LR quadrant

2245 MHz 23.89 dBiC 4.1 30.35


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PROTOTYPE READY FOR TESTING

PROTOTYPE INTEGRATION:

SUPPORT MECHANISM POSITIONING MECHANISMEM TRANSPARENT ARMS

BEAMS ARE STEERED USING ONLY LOW-POWER

SERVOMECHANISMS


33PROTOTYPE TESTINGIN OSU/ESL COMPACT RANGE

1. Handsome Grad Student2. Old professor3. Smart engineer


34Calibrated S band Boresight Gain

Measurements in outdoor area

~17.3 dBiL


35Calibrated S band Boresight Gain

Measurements in OSU compact range


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Compact Range - Boresight @ 2170 MHz (270/0 cut)

UR UL LR LL Array Array-cable, div

H (dBiL) 14.50 / 13.78

10.91 / 11.34

14.49 / 14.11

9.32 / 7.08

15.97 / 14.12

19.35 / 17.50

V (dBiL) 13.92 / 14.44

10.46 / 11.63

14.96 / 13.93

9.68 / 8.67

15.64 / 13.84

19.02 / 17.21

RHCP (dBiC)

17.09 / 17.10

13.69 / 14.44

17.67 / 17.02

12.51 / 10.92

18.75 / 17.09

22.12 / 20.36

HPBW (deg)

8.5 / 13 12.25 / 8 8.75 / 8 8 / 9 5 / 5 5


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Boresight @ 2230 MHz (270 cut)

UR UL LR LL Array Array-cable, div

Syn. Array

H (dBiL) 12.18 9.78 13.87 6.50 13.89 17.26 19.89

V (dBiL) 12.78 9.72 12.70 6.36 13.86 17.23 18.72

RHCP (dBiC)

15.24 12.76 16.26 9.44 16.81 20.18 22.28

HPBW (deg)

8 9.5 8 7.5 5 5 4


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Full Array gain study

Freq Boresight Gain

HPBW (deg)

HPBW gain (50% eff)

Theoretical 2230 MHz 32.06 dBiC 4.2 30.14

Outdoor 2020 MHz 22.05 dBiL / 22.23 dBiL

4 30.56

Anechoic Chamber

2170 MHz 22.12 dBiC 5 28.62

Synthesized from LR quadrant

2245 MHz 23.89 dBiC 4.1 30.35

In tracking down where the 10 dB went, we discovered that the silver printed on Mylar had slowly oxidized. Both the FSS ground plane elements and the radiating elements were now resistive. (20 to 50 ohms end-to-end!)

As expected

Too low


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SUMMARY OF RESEARCH SO FAR

WE BUILT AND TESTED A 3-ANTENNA SYSTEM

•PARTNERS: (SBIR PHASE 1 AND 2) (PHASE 3 HOPEFUL)•SPAWAR SAN DIEGO•THE OSU ELECTROSCIENCE LAB. (ERIC WALTON)•SYNTONICS LLC (BRUCE MONTGOMERY)

PROBLEMS OVERCOME: (DESIGN, CONSTRUCTION , TESTING)

• EM TRANSPARENT RADIATING ELEMENTS• EM TRANSPARENT FSS GROUND PLANE • EM TRANSPARENT DIELECTRIC SUPPORT PANEL• EM TRANSPARENT TRANSMISSION LINE FEED SYSTEM• EM TRANSPARENT SUPPORT ARMS• EM TRANSPARENT PANEL SUPPORT STEERING MECHANISM/CONTROL• TEST AND EVALUATION PROCESS

AND IT WORKED VERY WELL (GAIN; SIDELOBES; POLARIZATION; MUTUAL INDEPENDENCE)


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FUTURE RESEARCH EXPECTED:

• (6.1 research program)• GENERALIZE THE DESIGN OF FSS TRANSMISSION LINE FEED NETWORKS

(this is a PHD problem & is now in progress (Eugene Lee) ) • GENERALIZE THE DESIGN OF THE MULTIPLE ARRAY SYSTEM (other groups

will need to do their own specialized designs)• (6.2 research program)• OPTIMIZE THE DESIGN OF THE SYSTEM COMPONENTS (ELEMENTS, FSS,

TRANSMISSION LINES) (better & lower cost components, interconnections and structural supports to be developed)

• OPTIMIZE THE PRINTING OF COPPER OR SILVER LINES ON MYLAR (practical chemistry problems to be overcome)

• OPTIMIZE THE INTEGRATION OF THE “STACK” (better materials, low dielectric adhesives, interconnections between printed conductive lines and the transmission line network, possible spherical segment shapes for arrays)

• (6.3 research program)• BUILD AND TEST A FULLY OPERATIONAL PROTOTYPE SYSTEM

(demonstrate tracking of multiple satellites; provide operational data)• DEVELOP LOW COST AND EFFECTIVE MANUFACTURING PROCESSES FOR

HIGH VOLUME PRODUCTION (possibly in partnership with larger manufacturing corporation)


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QUESTIONS?

DR. ERIC WALTONOSU ELECTROSCIENCE

[email protected] 292 5051

Dr. Eric K. Walton

The Ohio State Univ. ElectroScience Lab

Columbus, OH; [email protected]

614 292 5051

Documents

ElectroScience Laboratory 1 DESIGN OF MUTUALLY TRANSPARENT ANTENNA ARRAYS JOHDPUR FEB. 28-29,2008 AND BANGALORE MAR. 3-4, 2008 Dr. Eric K. Walton The