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OPTIMIZATION OPTIMIZATION OF OF THE THE ELEMENTARY ELEMENTARY CELL CELL OF OF AA BROADBAND BROADBAND REFLECTARRAY REFLECTARRAY FOR FOR SPATIAL SPATIAL APPLICATION APPLICATION 1 2 1 2 3 3 Etienne GILLARD EtienneGIRARD GIRARD,1,Afshin AfshinZIAEI ZIAEI,2,Raphaël Raphaël GILLARD,1,Michel MichelCHARRIER CHARRIER,2,Hervé HervéLEGAY LEGAY3etetBéatrice BéatricePINTE PINTE3 IETR/INSA de Rennes, {etienne.girard, raphael.gillard}@insa-rennes.fr 1 1IETR/INSA de Rennes, {etienne.girard, raphael.gillard}@insa-rennes.fr 2Thales Research and Technology France, {afshin.ziaei, michel.charrier}@thalesgroup.com 2Thales Research and Technology France, {afshin.ziaei, michel.charrier}@thalesgroup.com 3Alcatel Space Industrie, {herve.legay,beatrice.pinte}@space.alcatel.fr 3Alcatel Space Industrie, {herve.legay,beatrice.pinte}@space.alcatel.fr
Circularly polarized incident wave
Reflected wave •Same polarization
Similar circular polarization of the re-radiated wave Phase shift π between Γyy & Γxx Γyy
•adjustable phase shift
TE10
Γxx
Z Incident wave
Incident wave
TE01
y x
TE10
TE01 Dipole
Studied cell
Ground plane Operating mode of the structure
Phased array Phase shift 2.α between each cell
L w1
α
Phase shift = 2 . α
h h : height, w1 : width, L : length
Studied structure
UNIVERSITE DE RENNES 1
Validation Validation of of the the passive passive cell cell
CCband band
Passive Passivestructure structure
Embedded Embeddedininaasquare squarecavity cavity
•Optimization •Optimizationcriterium criteriumto toreradiate reradiateaacircular circularpolarization polarization: : Good Goodcomparaison comparaison Theory Theory &&experiment experiment Comparison Phase Phaseshift shiftππbetween betweenΓyy Γyyand andΓxx Γxx Simulation & measure •Fixed length •Variable height •f = 5.7 GHz
•Optimization : process •Optimizationprocess: process: Varying Varyinggeometrical geometricalparameters parameters length length width width
LL W1 W1
height height hh
Difference Simulation - measure
Phase ( ° )
•Fixed length •Fixed heigth •Whole frequency range
12 10
•Results: : Results •Results: Optimization Optimizationwith with&&without withoutan anair airgap gap
8 6 4 5,5
5,6
5,7
5,8
5,9
frequency ( GHz )
Γyy - Γxx
Phase d (°)
Width
200
w1
350 250
180
Γyy - Γxx
Phaseqf( ° )
h = 6.86 mm Phase 172°
h
150
160 5,45
5,53
5,61
5,69
5,78
5,86
Fréquence ( GHz ) w1 = 1,62
w1 = 2,28
w1 = 2,92
Height
50
5,94
Optimized structure
-50 0
0,76 1,86 3,81 5,33 6,86 8,38 13,7 22,1 29
h ( mm )
without an air gap Phase ( ° )
Γyy - Γxx
Γyy - Γxx
Phase ( ° ) 190
350
L
300 L=16.59 mm
250 200
L=21.14 mm
Length
Optimized structure
180 170 160 5,45
5,53
5,61
5,69
5,78
5,86
Frequency ( Ghz )
180°
150
Length 16,59 mm
5,94
with an air gap
Length 21,14 mm
11,4 15,3 16,6 17,9 18,5 19,8 21,1 22,4 23,1
Dipole length
Optimization Process
UNIVERSITE DE RENNES 1
Operation Operation of of the the active active cell cell Ku band
•Optimization criterium to reradiate a circular polarization : Phase shift π between Γyy and Γxx
Active structure : MEMS Switches
•Optimization process: process:
Embededed in an hexagonal cavity
Varying geometrical parameters Inserting switches and polarization lines •Results: Results: Optimization of an active cell Phase Shift Phase ( ° ) Ey Reference
120 -120°
70 20 -30 17,76
Ey Rotation
18,06
18,36
18,67
18,97
19,27
frequency ( GHz )
y x Γyy - Γxx Phase ( ° ) 195 190 185 180 175 170 17,8 18,0 18,2 18,4 18,6 18,7 18,9 19,1
Frequency ( GHz )
Optimized structure with MEMS switches Axial Ratio AR (dB) 2 1,5 1 0,5 0 17,80 18,03 18,27 18,51 18,75 18,99 19,23
Frequency ( GHz )
Conclusion Conclusion:: The wave re-radiated by the unit cell of the reflectarray have a similar polarization and a chosen phase shift. shift The optimization process has been shown for a passive cell : Use of an active cell with MEMS Switches permits to steer the re-radiated wave.
UNIVERSITE DE RENNES 1
