UWB Slot Antenna In the 3-9GHz band ppsx

UWB
SLOT
ANTENNA
IN
THIE
3-9
GHZ
BAND
Jose
Manuel
Pidre
Mosquera*,
Maria
Vera
Isasa.
Dpto.
Teoria
de
la
Sefial
y
Comunicaciones.
Universidad
de
Vigo.
Spain.

Introduction
Recently
an
emerging

ultra-wide
band
(UWB)
technology
is
on
development.
It
requires
hard
design
specifications
for
antennas
over
a
very
wide
bandwidth.
U.S.
Federal
Communication
Commission
(FCC)
defines
UWB
as
higher
than
20%

fractional
instantaneous
bandwidth.
Short-pulse
UWB
technology
is
applied
in
communication,
radar
and
precision
radiolocation
[I
].
One
of
last
applications
for
UVWB
technology
is
breast
tumor
detection
[2].
In
this

detection
system,
the
antenna
has
to
work
in
frequencies
ranging
from
3
to
9GHz.
In
addition,
the
impulse
response
has
to
be
short,
constant
radiation
pattem
over
the
band
and

low
return
losses.
One
of
the
most
promising
antennas
that
can
meet
these
design
goals
is
the
ultra-
wideband
magnetic
antenna
[3]
[4].
The
behavior
of
this
antenna
in
the

3-9
GHz
range
is
presented
in
this
paper.
An
V-model
and
the
use
of
a
back-absorber
layer
in
order
to
improve
its
performance
is
analyzed.
A
prototype
has
been
built

and
measured.
UWB
Magnetic
slot
antenna
The
antenna
consists
of
a
leaf-shaped
slot,
excited
across
the
gap
as
can
be
seen
in
figure
1.
The
radiated
fields
are
orthogonally
polarized

to
the
longitudinal
slot
axis.
Figure
1.
UWB
Magnetic
slot
antenna.
Original
flat
configuration
(right
)
and
proposed
configuration.
(in
the
left)
0-7803-8883-6/05/$20.00
©2005
IEEE
508
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In
[3]
is

defined
the
width
of
the
slot
w
as
we
move
across
longitudinal
slot
axis
1:
w=
cos(
[l-c
]
I
<)
(1)
where
Xo
is
the
wavelength
in
the
center

frequency.
A
deeper
analysis
of
equation
1,
reveals
this
ratio
between
maximum
slot
width
W
and
slot
length
L:
W
1
-
=
-
=
0.0625
(2)
L
16
The

antenna
was
evaluated
using
the
software
packages
IE3D
and
XFDTD.
IE3D
is
a
commercial
method
of
moments
code
[5].
XFDTD
is
a
commercial
code
based
on
FDTD
algorithm
[6].
Both

can
deliver
radiated
fields
and
input
impedance
of
simulated
devices.
IE3D
is
very
fast
evaluating
planar
slots.
So
we
have
employed
it
to
study
how
the
slot
input
impedance
changes

with
dimensions.
XFDTD
is
a
powerful
tool
to
simulate
3D
devices
in
time
domain.
It
was
very
useful
to
analyze
the
antenna
with
different
bending
angles.
Starting
with
slot
dimensions

obtained
from
(1)
for
6GHz,
several
simulations
were
made
changing
the
W/L
ratio.
We
found
that
increasing
slot
dimensions
the
matching
bandwidth
increases
and
the
frequency
band
where
radiation
pattem

does
not
change
decreases.
In
order
to
get
an
ultra-wide
matching
band
maintaining
the
broadside
maximum
radiation,
a
longer
slot
bent
across
H-plane
is
proposed,
as
figure
I
shows.
After

studying
several
angles,
we
have
found
an
optimal
bending
of
58°
when
L=2X0
and
W=X/2
(W/L=1/4,
Xo=50mm).
Figures
2
and
3
show
the
simulated
radiation
pattern
of
this
configuration
in

E-plane
and
H-plane.
The
pattern
still
needs
some
corrections:
sidelobes
and
back
radiation
can
be
suppressed
with
absorber
sheets.
13
Ghz-4
Ghz
-5
Ghz
.6
Ghz-7
Ghz-6
Ghz*9
Ghz
I

9=
.
\
-
-

I-
-

T


I-




8
4
~~~~
\i-

i
I '



7
5-
-L \-, i

/

0
1
0
20
30 40
50
60
70
80
90
Theta
[Grados]
para
Phi
=
0°
Figure
2.
Simulated
E-plane
Gain
Magnitude.
509
Authorized licensed use limited to: Phan Phuong. Downloaded on January 14, 2010 at 03:11 from IEEE Xplore. Restrictions apply.
7

i-

,

Ii
~0
0
20
40
60
80
100
120
140
160
Theta
[Gradosi
pata
Phi
-
900
Figure
3
Simulated
H-plane
Gain
Magnitude.
Results
and
Discussion
A

prototype
with
the
mentioned
dimensions
was
built
and
measured.
The
prototype
was
built
in
0.5mm
brass,
and
a
sheet
of
eccosorb
[7]
was
employed
as
absorber.
Figure
4
shows
the

measured
and
simulated
input
impedance.
The
measurement
is
comparable
to
the
simulation
result.
Therefore,
if
we
feed
the
antenna
with
a
suitable
matching
network
the
antenna
would
be
well
matched

over
the
entire
desired
frequency
band.
Measured
and
simulated
gain
in
broadside
direction
is
plotted
in
figure
5.
Measurement
'4
SirTulation
Figure
4.
Input
impedance
from
3GHz
to
6GHz.
Simulation

and
Measurernent.
Ga.in
i.
Bmdrdd
dheti
0
1~~~~~~~~~~~~~
385
485
585
6885
75
Frr.qu0ny
(G3I)
Figure
5.
Gain
in
broadside
direction.
Simulation
and
Measurement.
510
Authorized licensed use limited to: Phan Phuong. Downloaded on January 14, 2010 at 03:11 from IEEE Xplore. Restrictions apply.
Conclusions
and
Future
Work

The
UWB
magnetic
slot
antenna
can
be
designed
in
order
to
meet
challenging
specifications
over
a
very
wide
frequency
band.
The
patented
design
of
[3]
was
analyzed,
and
some
changes

are
proposed
in
order
to
get
better
return
losses
without
radiation
pattern
deterioration.
We
built
a
prototype
increasing
the
dimensions
published
in
[3]
and
bending
the
antenna
580.
An
absorber

sheet
was
added
in
order
to
correct
undesired
sidelobes
and
back
radiation.
Measurements
were
very
similar
to
simulation
results,
and
both
comply
with
proposed
objectives
Acknowledgment
This
work
was
supported

by
Xunta
de
Galicia
(PGDITOITIC32201PR)
and
FEDER-CYCIT
(TIC2003-01432).
References:
[1]
R.J.
Fontana
"Recent
System
Applications
of
Short-Pulse
Ultra-Wideband
(UWB)
Technology".
IEEE
Trans.
Microwave
Theory
and
Techniques.
Vol.
52
N
9.

September
2004.
Pp.
2087-2104.
[2]
E.J.
Bond,
X.
Li,
S.C.
Hagness,
"Microwave
Imaging
via
space-time
beamforming
for
early
detection
of
breast
cancer".
IEEE
Trans.
on
Antennas
and
Prop.
Vol.
51.N°8.

August
2003.
Pp.
1690-1705.
[3]
M.
Barnes
"Ultra-Wideband
Magnetic
Antenna"
US
Patent
6091374.
July
2000.
[4]
H.G.
Schantz,
M.
Barnes
"The
COTAB-UWB
magnetic
slot
antenna".
IEEE
APS
Int.
Symposium
2001,

Vol.4,
July
2001.
Pp.
104-107.
[5]
Zeland
Software
Inc.
"IE3D
User's
Manual".
January
2001.
[6]
"XFDTD
Reference
Manual.
Version
6.0".
Remcom
Inc.
2003
[7]
Emerson&Cuming
Microwave
Products.

511
Authorized licensed use limited to: Phan Phuong. Downloaded on January 14, 2010 at 03:11 from IEEE Xplore. Restrictions apply.