JOURNAL OF L ATEX CLASS FILES, VOL. 14, NO. 8, AUGUST 2015 1 [600847]

JOURNAL OF L ATEX CLASS FILES, VOL. 14, NO. 8, AUGUST 2015 1
A novel antenna for Galileo system for automotive
applications
Alina-Mihaela Badescu, Member, IEEE, Cristina-Adelaida Heiman
Abstract —The abstract goes here.
Index Terms —Galileo system, novel antenna, multi-frequency
I. I NTRODUCTION
ONE of the first navigation system is NA VSTAR-GPS
[1]-[3], the military configuration (24 satellites on orbit)
being finalized at the end of 1995. Another important system
is the Russian GLONASS, started in the same period and
available for the civilians in the ’90. Due to the incompleteness
of the satellite segment, the availability and accuracy of the
system are limited [4].
In 2002 the European Commission approved the Galileo
navigation system, the first system oriented on civil applica-
tions [5]. The system represents an alternative to GPS and
GLONASS, and it was designed for a smaller and more stable
error in positioning.
On the market are available receivers (with corresponding)
antennas for GPS/GLONASS [6], [7], or a combination of
GPS/GLONASS/Galileo [8], the receivers dedicated to Galileo
only being almost in-existent. The situation is similar for the
automotive industry, and is becoming bothering since more
and more companies are working on prototypes for intelligent,
self driving cars that relay on navigation systems. The work
presented here addresses the development of a common tech-
nology multi-frequency antenna for Galileo professional users
that can be mounted on cars for navigations with the help of
Galileo satellites. We aim to enable the possibility of using the
same type of antennas in different professional applications.
The Galileo system delivers 10 signals with right hand
circular polarization. Out of this 3 are pilot signals (with no
actual data) freely available to all users in the bands E5 (1164-
1215 MHz), E1 (1559-1592 MHz), and E6 (1258-1298 MHz).
Moreover, Galileo is more reliable than other systems because
it informs users about the possible errors or interruptions.
Currently the GNSS antennas are designed on a case-by-
case basis for specific applications and therefore lack the
technological versatility to be implemented for alternative
purposes other than the ones initially devised for. Mass market
applications are currently oriented to use the open service of
Galileo on E1. However, the different professional markets
will make use of advanced multi-frequency (E1/E5) of Galileo
as well as interoperability with other constellations, most
notably GPS. However, in the medium term, it is expected that
mass market applications will benefit as well from the multi-
frequency, bringing the need for antennas that can support a
wider bandwidth to incorporate the necessary frequencies.
A.M. Badescu was with the Department of Telecommunications, University
POLITEHNICA of Bucharest, email:[anonimizat] multi-frequency (i.e. E1 and E5) antenna should be
successfully used to support automotive applications requiring
high accuracy, high robustness and high reliability. The long
term objective is also to have an antenna commercially ready
with a competitive cost.
The design of a multi-frequency antenna represents a rel-
atively difficult task. Studies have shown that for several
frequency bands, patch antennas tend to be difficult to design,
especially when, as for some GNSS signals, the bandwidth
is relatively high [9]. The problem is that for commercial
receivers as the one mounted on vehicles, the antenna needs to
be cheap. For a dual-frequency patch design, stacked patches
have been proposed [10], [11], and some single-layer slotted
patches [12], [13] which are more expensive to produce. One
triple-frequency GPS choke-ring antenna is a quite large [14].
So an inexpensive multi-frequency antenna design still seems
some way off.
One of the main difficulties connected to antenna designed
for satellites applications is connected to multipath reflections
suffered by the signal emitted from the satellite, which triggers
changes in the polarization of the signal. Other important
errors are due to total absorption of signals (atmosphere, veg-
etation etc.). The signals coming from near horizon are harder
to be detected due to higher radio noise and interferences thus
previous applications concentrated on antennas that rejected
this signals. A different strategy is presented in this work.
We will design an antenna that shows good performances
at low elevation angles, since this can be easier improved,
or integrated in arrays that enhance performances at higher
elevation.
The design of the antenna is presented in section II. The
results regarding the performances are presented in section
III. Last section summarizes our conclusions.
II. A NTENNA GEOMETRY
During the investigation the procedure which was utilized
targeted the calculations of the properties of a certain type of
antenna with the help of NEC in order to be able to construct
an antenna as precise as possible. The geometrical and elec-
trical factors are essential in modelling a wire structure. The
circumference of a wire should be really small compared to
the wavelength.
NEC is computer software that uses a special algorithm
which enables to calculate, for different types of antennas, the
electromagnetic response. The code is based on the method
of moments solution of the electric field integral equation for
thin wires and the magnetic field integral equation for closed,
conducting surfaces. It uses an iterative method to calculate
the currents in a set of wires, and the fields that result.

JOURNAL OF L ATEX CLASS FILES, VOL. 14, NO. 8, AUGUST 2015 2
Fig. 1. Antenna geometry
The analyses method divides each wire into segments with
dimensions in the range of 0.01 to 0.1 wavelength; it is very
important to avoid shorter and also longer segments.
The investigations where performed for many configurations
of double-folded dipoles, tilted at different angles, starting
with [15]. We obtained best results for two crossed perpen-
dicular dipoles of lengths of 0:03492m connected to a
0:0622m the vertical rod (figure 1). The wire circumference
was set to 3.2 mm to obtain enough mechanical stability. The
construction of the antenna was done using copper wires.
The antenna proposed and presented in figure 1 is made
from three radiating elements: two crossed modified folded
dipoles and one vertical one. The coverage in the zenith
direction is provided by the crossed dipoles; the low elevation
angles are covered primarily by the vertical dipole. Due to
the symmetry and orthogonality of the structure it is expected
that in the zenith direction the performances of the antenna
to be not so good. However, we are mostly interested in the
performances at low elevation angles since signals coming
from near horizon are harder to be detected due to higher
radio noise and interferences.
The characteristic impedance was set to 200
(figure
2), a compromise that is closest to both matching central
frequencies of bands E1 (1.57 GHz) and E5 (1.19 GHz).
For a circularly polarized field to be radiated it is ideal that
the currents in the elements to be in quadrature; obviously
this will not happen for all the directions. The main goal was
to obtain right-hand elliptical polarization at lowest possible
elevation angles. Assuming that the transmitting antenna has
a right-hand circular polarization, the polarization loss PL in
dB will be:
PL= 10 log10[1
2r
1 +r2] (1)
whererrepresents the axial ratio (AR), i.e. the ratio of the
minor axis to the major axis [16].
III. R ESULTS
Our efforts in designing the antenna concentrated to meet
the demands connected to low elevation signals, and multipath
propagation. We were interested to build a simple antenna to
meet requirements for both pilot carriers of Galileo, E1 and E5.
1000110012001300140015001600170018001900200005001000
Frequency [MHz]R [Ω]
10001100120013001400150016001700180019002000−5000500
X
[Ω]Fig. 2. The impedance of the antenna: the continuous line represents the real
part of the impedance and the line marked represents the imaginary one
Fig. 3. The VSWR for the E1 and E5 bandwidth
Simulations in figure 3 showed good voltage standing wave
ratio (VSWR) values, in the interval (1.66-1.73) for the E5
band, and in (1.36-1.55) interval for the E1 band.
The capacity of the antenna to reject other signals and polar-
izations were analyzed. One of the main difficulties connected
to antenna designed for satellites applications is connected
to multipath reflections suffered by the signal emitted from
the satellite, which triggers changes in the polarization of the
signal. The computations made with NEC for a set of radiation
patterns over an infinite ground plane were done for the and
planes for both EandEpolarizations. The infinite ground
plane was considered because the antenna should be mounted
on the metallic cover of a vehicle.
The gain is shown in figures 4 and 5 as a function of
zenith angle (the azimuth was fixed to a random value of
90 deg.) for E,E,ETandERHCP . The total gain was
calculated as ET=E2
+q
E2
, while the gain for right-
hand circular polarization ERHCP was obtained by adding the
polarization loss given by (1) to the total gain obtained from

JOURNAL OF L ATEX CLASS FILES, VOL. 14, NO. 8, AUGUST 2015 3
−50 0 50−20−15−10−50
θ [deg.] (f=1.19GHz, φ=90o) G [dB]

ETEφEθERHCP
Fig. 4. Computed patterns in - plane ( = 90o)
Fig. 5. *
Computed patterns in - plane (= 90o)
NEC. Except at the low zenith angles (which was expected due
to the construction of the antenna) the total gain and circular
polarization gain can be considered flat.
The same computed gains in the plane are shown in
figures 6 and 7, but for a zenith angle of = 60o. As in figures
4 and 5 the antenna patterns for different azimuth angles in
theplane were similar.
From the computations we were able to observe that in the
E5 band there is a uniformity of the total gains. For the E1
band (figure 5b) the total gain is pretty uniform but with a
small exception at azimuth angles near 90 deg. and 300 deg.
0 100 200 300−10−8−6−4−202
φ [deg] (f=1.19GHz; θ=60o)G [dB]

ETEφEθERHCPFig. 6. Computed patterns in - plane ( = 90o)
0 100 200 300−10−8−6−4−202468
φ [deg] (f=1.57GHz; θ=60o)G [dB]

ETEφEθERHCP
Fig. 7. Computed patterns in - plane ( = 90o)
in the form of a slight depressions.
As mentioned already the antenna for Galileo navigation
signals must be well matched in the relevant frequencies and
be Right Hand Circular Polarized. While at the zenith it is
not difficult to achieve good axial ratio (AR), the AR near
the horizon is much more problematic. In figures 6 (a and b)
are shown a complete set of computed patterns for the right-
hand circular polarization in the plane for azimuth angles
of 0 deg., 45 deg., 90 deg, and 135 deg. It was seen that
for small elevation angles the circular polarization coverage is
very good for both bands E5 (figure 8) and E1 (figure 9). This
was detailed in figures 10 and 11.

JOURNAL OF L ATEX CLASS FILES, VOL. 14, NO. 8, AUGUST 2015 4
−100 −50 0 50 100−30−25−20−15−10−505
θ [deg.] (f=1.19GHz)G [dB]

φ=0oφ=45oφ=90oφ=135o
Fig. 8. Computed right-hand circular polarization patterns in - plane
(f=1.19GHz)
−100 −50 0 50 100−30−25−20−15−10−505
θ [deg.] (f=1.57GHz)G [dB]

φ=0oφ=45oφ=90oφ=135o
Fig. 9. Computed right-hand circular polarization patterns in - plane
(f=1.57GHz)
The frequency dependence of the antenna was examined;
the radiation pattern did not change much over the considered
bandwidth (figure 12). However from figure 2 one can see that
the antenna impedance is more stable in the E1 band.
IV. C ONCLUSION
The objective of this investigation was to show that it
is possible to obtain circularly polarized coverage especially
at low elevation angles using a double-folded dipole. The
initial results are very encouraging. Whereas many circular
polarization antennas that are used for satellite navigation
0 100 200 300−3−2−10123
φ [deg.] (f=1.19 GHz)G [dB]

θ=50o
θ=60o
θ=70o
θ=80oFig. 10. Computed patterns in - plane (f=1.19GHz)
0 100 200 300−6−4−2024
φ [deg.] (f=1.57 GHz) G [dB]

θ=50o
θ=60o
θ=70o
θ=80o
Fig. 11. Computed patterns in - plane (f=1.57GHz)
require complex phasing networks, the antenna presented here
is fed directly from a coaxial line and may provide a very
low-cost option for achieving the desired coverage.
The performances of the same antenna were also simulated
in the case of the antenna positioned 1m above ground. The
gain increased by 2-3 decibels in both bandwidth (with a
slightly better performance in the E1 band) thus such an
antenna can be successfully used in other types of geolocation
applications that require high precision. To avoid interferences
from a-priori known locations, the performances of the antenna
can be increased by forming arrays to create nulls in the
radiation pattern in the direction of interferers.

JOURNAL OF L ATEX CLASS FILES, VOL. 14, NO. 8, AUGUST 2015 5
−50 0 50−15−10−505
θ [deg] (φ=90o) G [dB]

f=1.164GHz
f=1.19GHz
f=1.215GHz
f=1.559GHz
f=1.570GHz
f=1.592GHz
Fig. 12. Computed right-hand circular polarization patterns in -plane for E5
and E1 bands
REFERENCES
[1] L.B. Slater, From Minitrack to NAVSTAR: The early development of the
global positioning system , Microwave Symposium Digest (MTT), 2011
IEEE MTT-S International, ISSN: 0149-645X, 2011.
[2] A. Ariffin, N. Aziz, K.A. Othman, Implementation of GPS for location
tracking , Control and System Graduate Research Colloquium (ICSGRC),
pp. 77 81, ISBN 978-1-4577-0337-9, 2011
[3] M. A. Al Rashed, A real time GSM/GPS based tracking system based
on GSM mobile phone , Future Generation Communication Technology
(FGCT), Pp. 65 68, ISBN 978-1-4799-2974-0, 2013
[4] W. Lewandowski, A. Foks, Z Jiang; J Nawrocki, Recent progress in
GLONASS time transfer, Frequency Control Symposium and Exposition ,
Proceedings of the 2005 IEEE International, pp. 728 734, ISBN: 0-7803-
9053-9, 2005
[5] D. Coppit, K Sullivan, Galileo: a tool built from mass-market appli-
cations ,Proceedings of the 2000 International Conference on Software
Engineering, pp. 750 753, ISSN 0270-5257, 2000
[6] T Suzuki, M. Kitamura; Y . Amano; T. Hashizume, High-accuracy GPS
and GLONASS positioning by multipath mitigation using omnidirectional
infrared camera , Robotics and Automation (ICRA), pp 311 316, ISSN
1050-4729, 2013
[7] C. Tan, F. Song, T. Choke, M. Kong et al., A universal GNSS SoC with a
0.25mm2radio in 40nm CMOS , Solid-State Circuits Conference Digest
of Technical Papers (ISSCC), pp. 334 335, ISSN 0193-6530, 2014
[8] A. Reha, A. AMRI, O. Benhmammouch, A. Oulad-Said, Compact dual-
band Monopole Antenna for GPS, GALILEO, GLONASS and other Wire-
less Applications , International Conference on Multimedia Computing
and Systems, 2014
[9] N. Padros et al, Comparative Study of High-Performance GPS Receiving
Antenna Designs , IEEE Trans Antennas and Propagation, vol 45, no 4,
pp 698-706, 1997
[10] D. Pozar and S. Duffy, A Dual-Band Circularly Polarised Aperture
Coupled Stacked Microstrip Antenna for Global Positioning System , IEEE
Trans Antennas and Propagation, vol 45, no 11, Nov 1997, pp1618-1625;
[11] L. Boccia et al, A high performance dual frequency microstrip antenna
for Global Positioning System , IEEE Antennas and Propagation Soc Int
Symp, vol 4, pp 66-69, 2001
[12] X. Lan, A novel high performance GPS microstrip antenna , IEEE
Antennas and Propagation Soc Int Symp, vol 2, pp. 988-991, 2000
[13] Fan Yang and Rahmat-Samii, A single layer dual band circularly
polarized microstrip antenna for GPS applications IEEE Antennas and
Propagation Soc Int Symp, vol 4,pp 720-723, 2002[14] B.R. Rao et al, Triple Band GPS Trap Loaded Inverted L Antenna Array ,
MITRE Corporation, 2002, http://www.mitre.org/work/tech papers/tech
papers 02/rao triband/
[15] E. E. Altshuler, Hemispherical Coverage Using a Double-Folded
Monopole , IEEE Trans on Antennas and Propagation, VOL. 44, NO. 8,
pp 1112-1119, 1996
[16] C. Balanis, Antenna Theory: Analysis and Design 3rd Ed., London,
England: Wiley, 2005