pre-fractal resonant rings for compact spiral antennas - toulouse/spc_contest/spc04_jere… ·...
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Pre-Fractal Resonant Rings for Compact Spiral Antennas
J. Valleau1, H. Aubert1, A. Bellion2, P. Pouliguen3, P. Potier3
1LAAS-CNRS Toulouse, 2CNES DCT/RF/AN Toulouse, 3DGA DS/MRIS Bruz
State of Art
Choice of Profile
Measures
Introduction
Pre-fractal profiles
Conclusions
Energy harvesting Wireless Power Transmission
Antennas need to receive energy over
wideband
Use of UWB antennas required Issue: Antenna sizes for low frequency applications Objective: Miniaturized UWB antennas
An innovative architecture for miniaturization of UWB antenna is reported in [1] :
Antenna with stacked crenelated metallic rings
rings
substrate
spiral -40
-35
-30
-25
-20
-15
-10
-5
0
0,7 0,8 0,9 1 1,1 1,2 1,3 1,4 1,5 1,6 1,7 1,8
|S11
| (d
B)
Frequency (GHz)
D=127mm D=80mm
D=80mm
Principal: Lowest operating frequency of such an antenna depending on:
Number of stacked metallic rings Unfolded length L of the ring’s contour (or fres) Position of different rings above the spiral
37% reduction of the antenna No degradation of the radiating performances
antenna thickness (height=λ/25) Limitation in fres & miniaturization with crenel profile Time-consuming EM simulation (difficult optimization)
Iteration Order Von-Koch Hilbert-
Inspired (HI) Peano-
Inspired (PI)
1
2
3
Modified Von Koch (MVK) [2]
New degree of freedom : the sine amplitude A high number of points required for a good definition
[1] O. Ripoche, H. Aubert, A. Bellion, P. Pouliguen, P. Potier, “Spiral antenna miniaturization in very high frequency band”, Antenna Technology and Applied Electromagnetics (Antem), 25-28 juin 2012
New degree of freedom :
iteration order
[2] H. Diez, H. Aubert, D. Bellot, A. Takacs, ‘Antenne hélice compacte à profil sinusoïdal modulant un motif fractal’, french patent pending CNES-CNRS n°04576-01/20.
1,05
1,1
1,15
1,2
1,25
0 0,05 0,1 0,15 0,2 0,25 0,3 0,35
Log
qual
ity fa
ctor
Q
Log (L/L0)
0,01
0,02
0,03
0,04
0,05
0,06
0,07
0,08
0,09
0,1
0 0,05 0,1 0,15 0,2 0,25 0,3 0,35
Log
reso
nant
freq
uenc
y in
log(
GHz
)
Log (L/L0)
lowest Q
Reference
Reference
lowest fres
Best trade-off
The choice of the most suitable profile in a given application is the results of a trade-off between two criteria
Primary criteria For a given L, a compromise needs
to be made between:
lowest Q lowest fres !
Two antagonist parameters
Application criteria In a given application, a profile
needs to be realizable and limit the computation time. We will choose a
profile with : lowest fractal
iteration
lowest number of replicas
-50-45-40-35-30-25-20-15-10
-50
0,8 0,9 1 1,1 1,2 1,3 1,4 1,5 1,6 1,7 1,8
|S11
| (d
B)
Frequency (GHz)
Gain (dBi) φ=0° φ=90°
Lowest frequency
1,8 GHz
3 GHz
5 GHz
9% diminution of the lowest operating frequency with the MVK profile without deteriorating the
radiation performances
9% 7%
Chosen L
State of Art
Pre-fractal profile
Profile Choice Measures
Characterization of new profiles Comparison of their resonant frequency and quality factor to the crenel Definition of criteria to choose the most suitable profile depending on the application
Measures of an antenna with the selected profile: 9% diminution of the lowest operating frequency without deteriorating radiation performances Greater reduction expected with more stacked rings