1. 1
High Gain Printed Ultra Wideband
Antenna Concept
Veselin Brankovic, Adalbert Jordan, Djordje Simic, Jens Weber, Jagjit Bal
TES Electronic Solutions GmbH; Stuttgart Germany
Abstract Ultra wideband (UWB) communication
systems are emerging on the short range communication
market covering variety of the application scenarios.
Fact that UWB Systems are based on utilising wide
frequency bands of operation makes specific
requirements for antenna solution quite demanding.
Antenna dispersion behaviour is critical for the system
performance. Printed low cost antennas with the
capability to be integrated on the same substrate with
the UWB front end are very suitable for different
applications. In many specific cases, having
asymmetrical data traffic like access point applications,
it is highly desired to have high gain printed UWB
antenna solution, being able to function as sector
antenna with wide azimuth beam width and moderate
beam width in elevation. In this paper, high gain UWB
printed antenna concept covering complete frequency
range from 3-10 GHz is presented. The antenna can be
easily integrated with UWB ICs on the same substrate,
offering inherently low cost solutions with antenna again
in the range of 7-10 dBi. Proposed concept has been
verified by simulations and finally confirmed by
measurements.
Index Terms- Multi band OFDM, IEEE 802.15.4a, Ultra
wideband (UWB), Printed Antenna, High Gain Antenna
I. INTRODUCTION
Ultra wideband (UWB) communication systems [1]-[2]
for both High Date Rate Approach (MB-OFDM, HDR) and
Low Data Rate Location and Tracking Approach (LDR-LT)
have some typical application scenarios requiring high gain
antenna solutions.
In the case of the HIDR applications, typical scenarios
might cover:
- Receiving multimedia streams from car dash board
to the seats having integrated displays (antenna integrated in
the seat)
Authors are with the TES Electronic Solutions GmbH, Zettachring 8,
Stuttgart Germany, Tel. +49 71172877450, TES Electronic Solutions is a
leading global B2B High Tech Company with strong advanced R&D on
UW1 Technology development and products deployment. www.tesbv.com
-AReceiving multimedia and data streams to the
displays in home and business environment (antenna
integrated in the display)
In the case of the LDR-LT typical application scenarios
might be:
- Receiving data of mobile tag in location and
tracking system as antenna ofthe access point.
- Receiving information from wireless sensors by
concentrator, having integrated antenna radiating in
dedicated space sector
In the state of the art printed antenna solutions several
different approaches have been reported, mainly providing
solutions based on monopole approach, for lower (3-5GHz)
, higher (6-10 GHz) and complete UWB band (3-10 GHz)
[3]-[4]. SMD solutions have been also promoted for lower
and higher UWB bands, usually being sensitive to the
implementation of the PCB ground surface, and usually
addressing one of the UWB bands. The common approach
is that the proposed antenna solutions provide omni
directional radiation characteristics, with limited gain
capabilities and generally no possibility to influence
radiation direction in the simple way. Recently, printed
broadband radiation elements have been investigated and
deployed in high gain printed antenna solutions [5]-[6].
II. CHALLENGES AND CONCEPT SOLUTION
A. Challenges & Requirements
The concept solution must be able to cope with
following three requirements:
- Planar printed radiation elements, with 50% of the
operation bandwidth related to the center frequency in the
manner that thickness of the dielectric substrates does not
essentially influence the performance of the antenna. This
may allow to deploy the concept on substrates of different
permittivity and thickness and allow easy integration of the
antenna with the front end
- Feeding network for radiation elements should be
implemented as planar printed circuit, being able to support
signals transmission using frequency non-selective planar
power splitters.
- A metallic structure, ideally printed, should be used
as reflector to shape the radiation pattern ofthe antenna

2. 2
B. Radiation Elements
In order to provide broadband operation of the elements
being able to be easily fed with printed structures, printed
circular dipoles have been proposed as radiation elements.
In this approach one half ofthe dipole is printed on one side
of the substrate and another part of the dipole on the
opposite side, being fed by balanced microstrip line like it is
shown in Fig. 1. Having half dipoles with circular or
ellipsoidal shapes as proposed in this paper, achievable
antenna bandwidths have been increased for about 20%
compared to approach published in literature [5] .
Figure 1 - Circular printed dipole radiation element; the second
part of the dipole is on the opposite side of the substrate.
Exponentially tapered strip is introduced to allow transformation
to unbalanced line and therefore assembly of the connector for
tests
The robustness to manufacturing tolerances is also
increased, meaning that proposed shapes could be easily
manufactured by low-cost printed technologies, even for
mm-waves applications. Moreover, the proposed antenna
shapes allow easier optimisation to meat required input
impedances, so mainly one parameter needs to be fine
tuned. Measured return loss of the printed antenna on the
R04003 substrate of 0.51mm thickens and Er of 3.38 over
the entire frequency band from 3 to 10 GHz is better than -
12 dB.
C. Feeding network implementationfor multiplied
dipoles
Implemented dipoles could be easily used in antenna
arrays to obtain higher directivity. Due to the nature of the
balanced microstrip line, deployment ofthe feeding network
on the same substrate where the radiation elements are
printed is straight forward. In order to ensure splitting ofthe
signals in the wideband manner, instead of using frequency
selective quarter wave-transformers, linear tapering of the
strips is proposed. This simultaneously addresses more
typical problems, like discontinuities, manufacturing
tolerance vulnerability and offers matching with satisfactory
results in entire band ofinterest.
t igure 2 - teeaing network outiookjor two raaiation aipoies
D. Antenna implementation with corner reflector
Symmetrical mechanical reflectors, built from bended
metal plate, may be used for shaping radiation diagram of
the printed antenna in azimuth. The substrate with printed
dipole structures with feeding networks is placed in axial
symmetry plane of the corner reflector through the narrow
cut slot, like presented in the Fig. 3a. Slight change of the
reflector position in the respect to the radiation elements,
which is initially around quarter wavelength on the center
operation frequency, combined with the variation of the
feeding network lines width and radius of the circular half
dipole may be used for final optimization of the antenna
characteristics.
A~OO
Figure 3a -High gain antenna outlook andphoto with bended
metallic reflector
UWB Antenna Array with "31D" reflector
0
-5
-10
co -
15'a
-520
c> -25
-30
-35
-40
- Simulation
Measurement
0 1 2 3 4 5 6 7 8 9 10
Frequency [GHz]
Figure 3b - Simulated and measured input reflection lossfor
high gain antenna with bended metallic reflector with excellent
matching between simulation and measurements; the same
substrates and size ofthe dipoles as in Fig] are used.

3. 3
The measured gain is 9.6 dBi at 4 GHz and the reflection
coefficient in the frequency range between 3 and 10 GHz is
below -10 dB. The dimensions ofthe antenna related to Fig.
3a are: 89 mm, wide, 63 mm long and the height of the
reflector is 40 mm.
The concept of the corner reflector has several
drawbacks like: increased manufacturing cost due to the use
of the bended metallic plate, mechanical issues connected
with exact placement of the substrate in the axial symmetry
plane of the metallic structure, and overall mechanical size,
which can be too big for some applications. Also, this type
of antenna has more nonlinear phase response since position
of its phase centre is not stable with frequency because of
reflector position. The graph on the Figure 4 shows the
impulse response of the antenna which illustrates that the
antenna can be used in systems which have system response
longer of Ins, like IR-UWB with 500 MHz bandwidth,
compatible with IEEE 802.5.4a standard. The deterioration
of the pulse shape for wider channels can make significant
influence on the system performance, so applicability of the
antenna in such systems is limited.
Impulse response
0,8
Figure 4 - Time response ofthe high gain antenna with 3D
reflector
On the other hand, with the change of the corner angle
and the size of the reflector radiation characteristics may be
influenced. So the main beam width in azimuth can be
varied between 60 and 150 degrees and also maximum gain
can be changed for approximately - 2.5 to 3 dB. Of course,
there are also corresponding changes in the beam width in
elevation direction.
III. HIGH GAIN PLANAR ANTENNA CONCEPT
In many application scenarios requiring high gain
antenna features, three common performance and
construction requirements are:
a) Half-space radiation pattern in azimuth (180° beam
width)
b) Moderate beam width in elevation direction (not to
wide, not to narrow) ideally about 60 degrees.
c) Flat construction of the antenna, without external
mechanical reflector, offering easy integration of the
antenna in end product, ensuring minimal production costs
and time.
Achieving those requirements is possible by
modification of the corner reflector approach. In the Fig. 5
novel design is presented. Instead ofhaving bended metallic
structure as the reflector, metallic surfaces are printed on the
same substrate as the dipoles. The basic distance from the
centre of dipoles to the central part of the reflector is
approximately quarter wavelength of the central frequency.
The proposed reflector is "following" the changes of the
printed dipoles and feeding network shape, forming two
banana-shaped plate reflectors. The antenna radiation
pattern is influenced by the reflector geometry and may be
optimized by further change of the reflector plate size and
shape. The distance of the printed metallic reflector to the
feeding line should be more than one strip width in order not
to influence the characteristic impedance of the feeding line
and to avoid possible discontinuities.
Suppressing "odd" mode of propagation in the vicinity of
the reflector may be provided in the manufacturing process
by "bridging" two reflector halves by bond wires or by other
means, ensuring the same potential ofboth reflector metallic
surfaces. Proposed concept has one essential feature that the
reflector portion of the printed metallic structure is
concentrated near to the structure edges and is considerably
small compared to the complete printed area. This can be
essentially used for placing the RF front end components of
the UWB communication system inside the reflector
structure. In that case no antenna connector is required and
compact high gain UWB solution is obtained.
Figure 5
reflector
!gain antenna concept withprinted metallic
A. Simulation and measurement results
Verification of the proposed concept is done by
simulation and finally by producing related prototypes.
E
-0,8

4. 4
Simulation is performed by using WIPL-D software [7], like
it has been done in the case of 3D reflector antenna.
Microwave substrate R04003 with Er of 3.38 and thickness
of 0.51mm is used, with 18pm copper thickness with hard
gold coating. The dimensions of the antenna are: 89 mm
times 63 mm, which is the same as the size of 3D reflector
antenna board, but in this case, the thickness of the antenna
is much smaller (0.5mm, without connector), enabling easy
integration in many space-restricted applications. Of course,
in some cost sensitive application low-cost substrate
materials like FR-4 can be used, with some reduction of the
achievable antenna gain due to the losses in the material.
In Fig 6 Input reflection loss (simulations and
measurements) for the planar high gain antenna is presented,
confirming expected performance in complete band of
operation better than -10 dB.
Measured and simulated results
0
-10
m -20
V
- 30
C/ -40
-50
-60
- Simulation
Measurement
2 3 4 5 6 7 8 9 10
Frequency [GHz]
Figure 6 - Simulated and measured reflection lossfor high gain
planar UWB antenna with printed metallic reflector
BRadiation pattern at four frequencies
Figure 7 -Measured antenna diagram in azimuthfor high gain
antenna concept with printed metallic reflector
Fig 7 shows measured antenna radiation pattern in
azimuth for set of frequencies, showing expecting behavior.
3dB beam width varies from 180 degree to 220 degree for 3
and 10 GHz respectively. From 5 to 7 GHz measured 3-dB
beam width is constant and is more as 250 degrees. Figure 8
shows simulated 3D radiation pattern at 4 GHz. 3dB beam
width of 250 degrees in predicted, what corresponds very
well with the measurements. The gain of the antenna is still
smaller as one obtained with previously described antenna
with 3D reflector, but it is compensated with wider radiation
angle and better phase linearity which results in more ideal
impulse response ofthe antenna. (Fig. 9.).
7
35
252-7
2. -7787e thWIu
2A83ee ._m
_7. 403 e 1
Figure 8 -Radiation pattern at 4 GHzfor high gain antenna with
printed metallic reflector
Measured impulse response of the proposed antenna
concept may be observed in the Fig. 9. The data is obtained
by using frequency domain measurements with two antennas
as described in [8]. The measured results look promising,
showing the peak of the second response maximum 7 times
less in absolute field strength, showing small antenna
dispersion in time, what is consequence of good antenna
phase linearity. It shows that the antenna can be successfully
used for both impulse-based and MB-OFDM UWB systems.
Impulse response
a)
-5-
E
1
0,8
0,6
0,4
0,2
0
-0,2
-0,4
-0,6
-0,8
-1
0,5 1 1,5 2 2,5 3 3,5 4 4,5 5
Time [ns]
Figure 9 - Measured impulse response oftheplanar high gain
antenna
For demonstration purposes, proposed antenna concept
is successfully integrated in the automotive seat to check the
typical application scenario on unsymmetrical distribution
of the video signals in car entertainment system. The data
transmission is performed from the dashboard to the seat,
which had a display mounted on the back as illustrated on
the Fig. 10. The antenna was placed on the side of the seat
above arm-rest position. The same scenario is compared
using an omni-directional antenna as a reference; showing
expected much higher performance, robustness and
-3 GFt
-5 GFt
-TGFt
9 GFtI-------

5. 5
resistance toward blocking with human body. The tests have
been performed with high data rate WiMedia compliant chip
sets from Wisair, being connected to the antenna via SMA
connector, using FCC radiation mask in 3-5 GHz range.
Figure 10 - Implementation of the high gain antenna for
demonstration of video streaming application in a car
entertainment system
IV. CONCLUSION
High gain UWB printed antenna concept operation in the
complete frequency band from 3-10 GHz is presented.
Coverage in azimuth of 180 degree with measured gain
between 7-8 dBi that have been verified by simulation and
measurements for the entire band. Proposed low cost single
printed antenna concept is able to be used for easy
integration of the UWB ICs on the same substrate without
cables and connectors. The design is compared to the
antenna using same radiating elements and suitable 3D
reflector, showing improvements in radiation diagram and
impulse response. Proposed antenna is advantageously
successfully tested and benchmarked against classic omni
directional printed antennas on typical video streaming
application. The practical implementation value of the
concept is therefore also confirmed. Realisation of the
antennas on very low cost substrates is possible with some
reduction in achieved overall gain.
V. ACKNOWLEDGEMENT
The work presented here has been partially performed in
scope ofthe European research project PULSERS, which is
partly being funded by the Commission of the European
Union within the 6th EU research framework.
The authors would like also to thank ENSTA- Paris
antenna laboratory for kindly supporting antenna radiation
pattern measurement activities on their facilities and
providing help in measurement data interpretation.
VI. REFERENCES
[1] Multiband OFDM Alliance, "MultiBand OFDM Physical Layer
Proposalfor IEEE 802.15 Task Group 3a", September 2004
[2] Anuj Batra, Jaiganesh Balakrishnan, Anand Dabak, et al.
"TI PHY layer proposal", IEEE 802.15- 03/ 141r4, IEEE
802.15.3aPHY layer Working Group, 2003
[3] Targonski, S.D.; Waterhouse, R.B.; Pozar, D.M.; "Design of
wide-band aperture-stacked patch microstrip antennas", Antennas and
Propagation, IEEE Transactions on Volume 46, Issue 9, Sept. 1998
Page(s): 1245 - 1251
[4] C. Y. Wu, C. L. Tang, and A. C. Chen.;"Compact Surface mount
UWB Monopole Antenna for Mobile Applications", Progress In
Elecromagnetics Research Symposium 2006, Cambridge, USA, March 26-
29.
[5] Nesic, A.; Brankovic, V.; Krupezevic, D.; Ratni, M.; Nesic, D.,"
Broadband printed high gain antenna with wide angle radiation in
azimuth" Antennas and Propagation Society International Symposium,
2001. IEEE Volume 2, 8-13 July 2001 Page(s):468 - 471 vol.2
[6] Nesic, A.; Radnovic, I.; Brankovic, V.; Ultra widebandprinted
antenna arrayfor 60 GHzfrequency range", Antennas and Propagation
Society International Symposium, 1997. IEEE., 1997 Digest Volume 2,
13-18 July 1997 Page(s): 1272 - 1275 vol.2
[7] WIPL-D High Frequency 3D EM Modeling and Simulation
Software,w
[8] W. Sorgel, F. Pivit, W. Wiesbeck ,"Comparison of Frequency
Domain and Time Domain Measurement Proceduresfor Ultra Wideband
Antennas," IEEE EMC Magazine, September 2004, pp3 1-35