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Electromagnetic Tools for Precise Ceramic Radome
and Antenna Characterization
Cynthia Junqueira*, Mario A. R. Canto**, Ediana Gambin*, Daniela Ronsó Lima*, Diovana de Moura Silva*,
Maurício Weber B. da Silva*, Gustavo R. Silvério*, Francisco C. L. de Melo*, Francisco Piorino Neto*, João M.
Kruszynski de Assis*, Marcelo B. Perotoni***, Marcelo Antonio Santos da Silva ****, Antonio Sérgio B. Sombra****
*Institute of Aeronautics and Space, IAE, Brazil {cyjunqueira@uol.com.br, edigambin@gmail.com,
dronsolima@yahoo.com, dbms10@gmail.com, mauricio.weber@gmail.com, gustavorsilverio@hotmail.com,
franciscofclm, franciscofpn, joaojmka@iae.cta.br}
**Industrial Fostering and Coordination Institute, IFI, Brazil, {marioafonsomarc@ifi.cta.br}
***Federal University of ABC, UFABC, Brazil{marcelo.perotoni@ufabc.edu.br}
****Federal University of Ceará, LOCEM, UFC, Brazil {marceloassilva@yahoo.com.br, sombra@ufc.br}
Résumé
Les applications aérospatiales requièrent l'emploi de matériaux supportant des ambiances extrêmes et les céramiques
sont un des candidats possibles. Ici le focus porte sur la caractérisation par des méthodes électromagnétiques
d'échantillons de radome réalisés en céramique. Cette contribution décrit la méthodologie de développement d'une
antenne de transpondeur en bande C recouverte d'un radome en céramique et destiné à un vol spatial. La céramique
retenue est de type aluminium-silicate (Mullite) pour laquelle trois compositions différentes sont analysées et les tests
standards accomplis. L'évaluation électromagnétique des échantillons (permittivité) a été effectuée avec des méthodes
non-destructives telles que Hakki-Colleman ou de type espace-libre. Un ensemble radome-antenne en bande C a été
conçu en technologie microstrip et employant une céramique Mullite d'épaisseur 5 mm, le prototype a été construit puis
évalué au laboratoire. Enfin, des mesures effectuées dans une chambre anéchoïde ont indiqué un excellent accord entre
simulations et résultats pratiques.
Mots-clefs: méthodes en électromagnétisme, radome céramique, méthodes non destructives, antenne.
Abstract
Aerospace applications demand materials that support critical environmental conditions and ceramics are one of the
candidates. Here, the focus is the application of electromagnetic methods to precisely characterize ceramic radome
samples. This work describes a steady methodology in development of a C band transponder antenna covered with
ceramic radome for flight applications. The chosen ceramic was the aluminum silicate (Mullite) and three different
compositions were analyzed and the ceramic standard tests were accomplished. Electromagnetic samples evaluation
(electrical permittivity) was performed with the application of non destructive methods as Hakki-Colleman and FreeSpace. A C band set radome-antenna was designed with microstrip technology and employing a Mullite ceramic with 5
mm thickness, the prototype was build and evaluated at the laboratory. Finally, measurements in anechoic chamber
indicates excellent conformance between the simulations and practical results.
Index Terms: electromagnetic methods, ceramic radome, nondestructive methods, antenna.
Introduction
In aerospace applications, ceramic radomes play an important role and deserve special attention. Aerospace
applications demand materials that support critical environmental conditions and ceramics are one of the best candidates
due to their characteristics. This kind of component works together with a communications system and contributes
decisively for the resultant array pattern, so its proper characterization is very important.
In this scenario, it is important to have a holistic view over all the parameters involved in the project, because,
altogether with the material electromagnetic characterization, it is necessary that the used materials follow the
aerodynamic, structural, environmental and mechanical constraints.
The chosen ceramic was the aluminum silicate (Mullite) [1-2] mainly due to the low specific mass, good resistance
to thermal shock and low dielectric loss properties. The development was based in three different compositions and
sintering temperatures.
The designed Mullite material was checked by X-ray diffraction. During the samples development several tests
were performed: Vickers hardness, bulk density, shrinkage rate and fracture toughness. The micro structural
characterization was done by electron microscopy scanning (SEM). The best observed results for density and formation
of the Mullite phase were presented for samples sintered at 1650°C.
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Regarding the electromagnetic evaluation, measurements using the Hakki-Coleman and Free-Space methods were
performed. Both are of non-destructive type and establish a complete understanding of the samples behavior during the
design process. Additionally they can be done at the current laboratory installations. The first one is based on the theory
of dielectric resonators and is well known in the literature [3-5]. The dielectric permittivity was obtained using an inhouse software based on the Kobayashi & Katoth [6] methodology.
The Free Space method, on the other hand, performs the characterization of planar material samples positioned
between a transmitter source and a receiver antenna [7], [8]. Associated to the instrumentation setup is the Thru-ReflectLine (TRL) calibration [9] and the Nicolson Ross Weiss (NRW) method [10]. For the electric permittivity computation,
a code was developed and validated against measurements [11]. Current laboratory installations allow the measurement
with the Ground-Reflect-Line (GRL) calibration method together with Keysight tools [12] and a Line-Reflect-Line
(LRL) calibration method using Anritsu vector network analyzer [13].
Here, the main analyzed problem is the application of electromagnetic methods to precisely characterize developed
ceramic radome samples. A methodology for the development of an aerospace C band transponder antenna covered
with ceramic radome is also presented. This developed laboratory will be also applied to characterize different others
planar materials, dielectric or magnetic.
This paper is organized in five sections. Mullite material and tests results of the methodology used in its
development are briefly discussed in section 1. Section 2 has the electromagnetic evaluation analyzed in detail. In
section 3 are presented the main measurements results of the characterization methods and the developed prototype.
Finally, concluding remarks are given in section 4.
1. Mullite
Mullite (3Al2O3.2SiO2) is a rare natural mineral. Being the only stable intermediate phase in the Alumina-Silica
(Al2O3-SiO2) system at atmospheric pressure, it is one of the most important ceramic materials. It is a phase of the
binary diagram Alumina-Silica whose mass corresponds to 71.8% of Al2O3 and 28.2% of SiO2. Mullite presents low
specific mass and excellent physical and mechanical properties at high temperatures, good shock response and fracture
resistance, thermal stability, low thermal conductivity and dielectric constant. Due to this, this material may have
optical and electronic device applications [14, 15].
The development was based on three different compositions and sintering temperatures. Mass percentages of
material for each composition are displayed at Table I.
Row Material
Caulim
Alumina CT3000
Fumed Silica
Potassium feldspar
Water
Percentages (%)
Composition I
Composition II
53
50
42
40
0
0
0
5
5
5
Table I Material Composition
Composition III
0
69
26
0
5
The samples were conformed by uniaxial pressure with pressure between 40MPa and 60MPa using mechanical
steel molds as showed in Fig. 1. The size of the samples was optimized for the Hakki-Coleman method electromagnetic
test.
Fig. 1. Mechanical steel mold
Sintering was performed in a rate of 10°C/min and 1 hour of heat treatment. It was studied the evolution of the
Mullita phase formation in the compositions, as a function of the variation of temperature (in a range of 1000°C and
1650°C). The porous, specific mass and water absorption were measured by the Archimedes technique. Results indicate
that compositions I, II and III have values of porosity and water absorption close to zero and density close to the
theoretical value (3.17g/cm3 ) with the increase of the temperature.
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We also observed that the pressure used in the compactation process will result in changes of the sample physical
properties. The test was performed varying the pressure from 40 MPa to 60 MPa. During the samples development
several tests were performed. The Vickers hardness was measured with five indentations in different sample regions. As
was expected, the Vickers hardness (HV) increases with the sample sintering temperature (T). Results are synthesized
on Table II.
T (ºC)
1600
1650
HV (GPa)
Composition I
Composition II
13
9
15
10
Table II Vickers hardness
The thermal shock was performed with a large range of temperature variations. For the temperature variations (∆T)
larger than 400°C it was observed smaller resistance (σ) of the samples in the analyses. For the composition II, samples
sintered at 1650°C shows resistance values in table III.
200ºC 400ºC 600ºC 800ºC 1000ºC
∆T Test
70.5
59.0
Weigth(N) 233.5 115.5 75.5
76.9
39.0
25.5
23.8
19.7
σ (MPa)
Table III Resistance (σ) with thermal shock
The Mullite was checked by X-ray diffraction. During the samples development several tests were performed:
Vickers hadness, bulk density, shringage rate and fracture toughness. The micro structural characterization was done by
electron microscropt scanning (SEM). The best results for density and formation of Mullite phase was presented for
samples sintered at 1650°C.
After the tests, the composition III was discontinued and the best samples reaching 96% of the theoretical density.
The feldspar into the composition seems to promote needle-shape grains. As the sintered temperatures increase, the
physical and mechanical properties of the sample become better and more attractive to be applied as a radome material.
In this context the Mullite, in composition I and II will be the candidates to be characterized as will be described in
the following sections. Fig. 2 shows Mullite cylindrical samples and planar plate build in the development phase.
Fig. 2. Mullite samples
2. Electromagnetic Evaluation
Related with the electromagnetic evaluation, it is possible to perform tests in Hakki-Coleman and Free-Space
methods. Both are non destructive and establishes a complete understand of the samples during the design process and
can be done at laboratory installations.
2.1. Hakki-Coleman Method
This method is based on the theory of dielectric resonators [3-5]. Several configurations were developed for
the Hakki and Coleman setup, and also studied by Courtney [5] and Kobayashi [6]. Hakki and Coleman analyzed the
TE0nl modes not considering the air gap effects between the conductive plates. In the work of Cohn and Kelly [16] the
dielectric constant measurements using the TE011 mode were discussed added to a calculation proposal where the air
gap was taken in account. Courtney in [5] discusses the Hakki and Coleman technique studying a radial setup for more
flexibility in the sample size and frequency range.
The dielectric characteristics measurements in the microwave range done with this methodology consists
basically in a cylindrical sample positioned between two copper plates. This configuration allowed the propagation of
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both TM and TE modes. The TE011 mode generally is the most easily identifiable. The schematic and experimental
setup can be visualized in Fig. 3. The resonator is excited by a vector network analyzer in a transmission mode. The
maximum values indicate the frequencies where the resonance occurs. Larger peaks mean higher losses indicating a
smaller quality factor. Generally, for cylindrical resonators with diameter/height ratios (D/H) close to one, the first
resonant peak is associated with the HEM111 mode and the second resonant peak with the TE011 mode. The TE011 mode
is used for the measurements because its propagations are mainly inside the sample but it is evanescent out of the
sample. Also, with TE011 mode we have only the azimuthal component of the electrical field and the error associated
with gaps between the copper plate and the sample can be negligible [17]. In this way, the second resonant peak is
considered for the dielectric constant and loss calculations by Kobayashi & Katoth [6] methodology. Fig. 4 illustrates
the results of transmission measurement.
Fig. 3. The schematic and experimental setup
Fig. 4. Transmission measurements results
The Hakki-Coleman method and associate software validation was performed together with the LOCEM –
Laboratory of Telecommunications and Materials Science and Engineering from Federal University of Ceará in Brazil
[18] where the validation process, tabulated electrical properties materials as (PTFE) Teflon, Alumina 99% and
polypropylene (PP) samples were measured in both laboratories. The LOCEM employs a Courtney resonator from
Damaskos Inc. [19]. During the period of validation of Mullite developed and produced by Materials Department
(AMR) at Institute of Aeronautics and Space (IAE), also the complete lot of samples were measured at IAE and verified
at LOCEM. In this way, together with the results of tests as described in section I, the best set of samples were
established.
2.2. Free-Space Method
The Free-space method characterizes planar material samples positioned between a transmitter source and a
receiver [7] as shown in Fig 5. Associated to it is applied the Thru-Reflect-Line (TRL) calibration [9] and the Nicolson
Ross Weiss (NRW) method [10].
Fig.5. Schematic diagram of a test setup [7]
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The free space methods may present systematic errors, mainly due to the mismatch between the antennas and the
propagation medium of the waves until the reference planes defined by the two surfaces of the sample. As indicated on
the literature [7], to obtain measurements results with quality, some requirements need to be observed as curvatures and
imperfections in the faces of the sample and metal plate used as a ground plane. They need to have parallel faces
positioned to the planes of the antennas apertures.
The TLR calibration procedure [9] is used to correctly measure the S parameters together with an in- house
developed and validated software [20]. After data calibration, electric permittivity is calculated by another algorithm,
such as the NRW method [21]. Fig. 6 shows a snapshot of the in house software screen for TLR calibration and NRW
calculations.
Fig. 6. Snapshot of the software screen
The Nicolson-Ross-Weir method (NRW) [2], [3] is based on the phenomenon of reflection and transmission on the
material whose characteristics are to be determined. These phenomena occur due to the difference between the complex
permittivity and the complex permeability of the two environments involved (inside and outside the material). The
complete step by step procedure was done by the research group to overcome some obstacles the method understanding.
It is presented in [21].
TLR calibration and NRW procedure by software implemented at the laboratory were performed with collaboration
with the Signature work group from Department of Reconnaissance and Security/Microwave and Radar Institute, from
the German Aerospace Center (DLR) [22]. For the TRL software validation, as can be observed in [20], a sample of
glass was used. This sample calibration was done in two ways, via vector network analyzer (VNA) Anritsu 37269A
embedded software at DLR facilities and via software developed in the laboratory. The frequency range of the
experiment was from 26 to 40 GHz.
The NRW software validation was performed in X band range (8.5 GHz to 12.5 GHz), with materials with tabulated
electrical properties, such as air, glass, FR4, acrylic glass, polyethylene [23] and Rogers RO3210 [24]. This frequency
band was chosen due to the laboratory VNA range limitation.
It was observed conformity between the responses of the software of both institutes, as well as the tabulated values
[24]. This consistency of the obtained results indicates acceptable reliability of the developed software.
As a complementary tool, the laboratory installations were complemented with development of a setup that allows
measurement with the Ground-Reflect-Line (GRL) calibration method [25] together with Keysight VNA and embedded
software [12]. The GRL method allows dielectric and magnetic materials characterization.
Another method of calibration also was performed in the laboratory; the so called Line-Reflect-Line (LRL) [26]
calibration provides an improved error compensation capability when measurements in waveguides, microstrip or
coaxial lines. Instead of using short, open and load patterns, the LRL calibration method uses the information of the
reflector ground plane and about the two distances involved: between transmitter antenna and reflector ground plane
(Line 1) and between the reflector ground plane and receiver antenna (Line 2).
The difference in length between Line 1 and Line 2 creates a set of measurements for the minimization of systematic
errors. The complete calibration consists in two transmission lines, reflection and isolation measurements. The
correction of error in this case is done by a software and using a VNA with temporal option. Equipments from
companies as Anritsu [13] and Rohde-Schwarz [27] are prepared for this kind of calibration and errors correction. In the
laboratory an Anritsu VNA complete our park of equipments. Using the calibrated data, material permittivity or
permeability can be computed with the NRW software.
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3. The Prototype: Results and Analysis
The radome-antenna prototype was analyzed using the developed facilities in the laboratory. A set of radome
samples were built and characterized. The available methods were evaluated in the laboratory and structural and
electromagnetic simulations were performed. The prototype was built, measured and analyzed.
3.1. Hakki-Coleman Measurements
Using the Hakki-Coleman method the electrical permittivity from Mullite samples was characterized. Fig. 7
illustrate one of transmission S parameter measurement with VNA and the values to be considered at the calculations of
dielectric constant (εr) and tangent loss (tanδ).
In general, a wave propagating in a dielectric medium undergoes losses, and the permittivity of the material can no
longer be represented by a real value. These losses can be attributed to a number of causes, including conduction and
relaxation phenomena in the dielectric and in impurities, molecular resonances, and molecular structure [28-30]. Loss
tangent (tanδ) is commonly used to characterize the loss at micro and millimeter wavelengths, even though the losses
may be due to other reasons than conduction. In general, ε’ and ε’’ are functions of frequency, although in many
applications they may be considered to be constant over a limited frequency band of interest [31-34]. The dispersive
dielectric properties can also depend on temperature.
These samples were arranged in sets of Mullite compositions and sintering temperatures. Table IV shows dielectric
constant and loss results from the compositions discussed in section I. The resonant frequency (Fr) is dependent of the
sample size, and for all samples sets were considered the ratio D/H equal to 2. The measurements at room temperature
are made in the TE011 mode at a single frequency dictated by dielectric constant and the size of the cylindrical sample
from as low as about 1GHz and up to 20GHz due to the laboratory VNA up frequency restriction.
Fig. 7. Transmission S parameter measurement from vector network analyzer
T (ºC)
1600
Composition
εr
tanδ
Fr (GHz)
I
6,41
0,0038
11,0943
II
6,34
0,0045
10,7775
1650
I
6,23
0,0071
10,7730
II
5,89
0,0036
11,5415
Table IV Dielectric constant and loss characterization by de Hakki-Coleman method
For a radome-antenna simulation and construction was chosen the Mullite composition sample whose dielectric
constant and loss were in accordance with the Mullite data available in the literature, antenna substrate availability and
the Mullite samples was considered to be reproducible. In this case, composition II with dielectric constant of 5.89 and
loss of 0.0036 were chosen for the electromagnetic simulations.
3.2 Free-Space Measurements
The complete setup for the measurements, the so called bi-static arch for free space measurements was installed at
IFI laboratories inside a semi-anechoic chamber and is showed at Fig. 8. It allows control for the antennas position,
incident angles and sample fixture. The IFI measurement setup is conditioned to measure in the band of frequency of
available conical lens horn antennas, between 4 GHz and 6 GHz. The sample dimensions are related with the antenna
focal area and a good choice ratio is around 2.5. Fig. 9 shows measurements done using TRL/LRL method, Anritsu
VNA and lens corrected conical horn antenna (RA4540-5) from Rozendal Associates [35].
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Fig. 8. Bi-static arch for free space measurements
Fig. 9. TRL/LRL method measurements with Anritsu VNA.
For the correct verification of the setup calibration, before the sample measure, for the required frequency band,
two standards are checked. In our case, the air (sample fixture empty) and a PTFE (teflon) plate were considered.
Figures 10 to 13 shows the results using a GRL method applied together with Keysight VNA and software.
Fig. 10. Permittivity – real part (ε’) - Air
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Fig. 11. Permittivity – Imaginary part (ε’’) - Air
Fig. 12. Permittivity – real part (ε’) – PTFE-Teflon
Fig. 13. Permittivity – Imaginary part (ε’’) – PTFE-Teflon
3.3. Structural Simulations
After measured the electrical permittivity and loss from several Mullite samples, structural simulations by finite
element method [36] were performed for a planar plate radome. These simulations give support for the materials and
mechanical specialists, aiding in decisions aspects as material composition, radome shape and thickness. Moreover,
they allow a pre-visualization of the structural integrity of the set radome-antenna when different forces and
environmental conditions are applied.
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Typical specifications for radome materials are related to each application and usually take into account
aerodynamic effects, wind load, differential values of pressure, space heating and kinetic erosion due to dust, rain or
other destructive impacts as stones or birds, as is the case for aircraft radomes. In this work the object of study will be
applied to the specific thermal and forces operating in the region of attachment of the radar transponder microstrip
antenna into the low orbit atmospheric Reentry Satellite (SARA), being developed by Institute of Aeronautics and
Space (IAE) [37].
The microstrip antenna substrate with dimensions of 34 mm x 36 mm will be protected by the Mullite radome and
will be located in the rear of the SARA module (http://www.iae.cta.br/site/page/view/pt.sara.html), subject to a single
flight at a predetermined period. Fig. 14 displays the forces model for simulations.
Fig. 14. Forces Model (N)
The assembly antenna-radome was analyzed at room temperature. It was fixed by 304 stainless steel screws in a
small rectangular depression in the SARA body. Using the software MSC Patran / Nastran [36], the model uses shell
elements and CQUAD4 topology with the minimum possible CTRIA3 elements [12]. As related in literature [4] and
according IAE internal reports [37], these resultant forces can occur in all SARA axes as briefly illustrated in Fig. 15.
The device will be subject to gravitational and aerodynamic loads.
Fig. 15. Resultant Forces
Table V shows the properties for the case study where it can be seen that the simulation provided a minimum
thickness equal to 4.6 mm. In red it is highlighted the minimum thickness to be considered for the radome material in
the simulated set.
Material Properties
Mullite
Thickeness (mm)
2.7
3
4
Runoff simulated voltage (MPa)
330
261
132
Displacement (mm)
9.42E-2 7.08E-2 3.33E-2
Strength at Yield (MPa)
90
90
90
Strength at Break (MPa)
150
150
150
Modulus of Elasticity (GPa)
145
145
145
Dielectric Permittivity (e')
6.2
6.2
6.2
Tangent of Loss
0.005
0.005
0.005
Table V Mullite properties
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4.6
91.7
2.34E-2
90
150
145
6.2
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Fig. 16 shows the loads at central and peripheral zone for a 4.6 mm radome thickness. Peripheral regions have no
directly loads applied, but are impacted as proximity to the side. Fig. 17 shows the behavior of the yield stress with the
change in thickness to the radome structure.
Fig. 16. Mullite loads in radome 4.6 mm thickness (MPa)
Fig. 17. Yield Stress
3.4. Electromagnetic Simulations
Together with the previous results, a C band radome-antenna assembly was designed using microstrip technology
and employing a Mullite radome with 5 mm thickness. The thickness of radome was chosen bigger then the minimum
appointed in the structural simulations only for the simplicity and to allow the use a pre-existent mold and surface
grinding set possibility. The design was analyzed with CST MWS [38] where the permittivity data collected by
experimental tests with Hakki-Coleman method was considered.
For the microstrip antenna the chosen substrate was Arlon GX-0300-55-11, thickness of 0.762mm, dielectric
constant 2.55, los tangent of 0.0022 and laminate with 1oz. cupper [39].
The Fig. 18 shows a lateral view of the CST antenna model. The prototype has rectangular geometry, coaxial probe
feed and linear polarization. The theoretical resonant frequency was chosen 5.7 GHz and the minimum bandwidth of
100 MHz, considering S11 magnitude ≤ -10dB.
Fig. 18. Microstrip antenna and radome CST model - lateral view
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The simulated results from input impedance and radiation pattern are showed in Fig. 19 and 20. Fig 19 shows the
reflection coefficient magnitude versus frequency. The magnitude of S11 is -26.45 dB at the resonant frequency and
bandwidth around 180 MHz.
Fig. 19. Reflection coefficient magnitude (S11) (dB)
Figure 20 illustrate the directivity on the plane ϕ=90°, where can be observed at the main lobe direction a small
displacement of ∆θ = 6° and amplitude value of 5.3 dBi. In the plane ϕ=0° the directivity shows values of 5.2 dBi,
where the displacement of ∆θ = 1°. These small differences are considered negligible and the antenna was built with the
patch geometric values from the simulations. Fig. 21 shows the radome-antenna assembly in the IFI anechoic chamber.
Fig. 20. Farfield directivity - ϕ=90°
Fig. 21. Radome-antenna assembly
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The measurements results were performed at the IFI anechoic chamber and are shown in fig. 22 to 25. The input
reflection coefficient magnitude can be observed at fig. 22, where the excellent impedance matching at frequency band
from 5.6 GHz to 5.9 GHz is highlighted. The experimental resonant frequency was 5.79 GHz and presents a S11 of 33dB. The measured Smith chart diagram is displayed at Fig. 23.
Fig. 22. Amplitude do coeficiente de reflexão de entrada
Fig. 23. Smith chart diagram
The radiation pattern and gain measurements were performed considering the frequency of 5.7 GHz. The fig. 24
and 25 shows the measurement results in comparison with the radiation pattern of a standard horn for a rectangular and
polar representation at the plane ϕ=90° respectively. The measured gain was 5.26 dBi and the results indicates excellent
conformance between the simulations and practical results.
Fig. 24. Rectangular radiation pattern representation - Gain (dBi) versus Azimuth angle (θ °)
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Fig. 25. Polar radiation pattern and Gain representation (dBi) versus Azimuth angle (θ °)
The displacement values between theoretical and experimental results can be explained by the radome-antenna
assembly and due to the quality in the surface grinding. These differences will be the starting point for future
investigations and process improvements.
4. Conclusions
The focus of this work is the application of electromagnetic methods to precisely characterize ceramic radome
samples. Additionally, a methodology for a radome-covered C-band transponder antenna design is presented, for
aerospace application. The chosen ceramic was Mullite, after its optimum composition and sintering temperature were
determined.
A study of several methods for permittivity and loss characterization was performed. Advantages and
disadvantages of the employed methods were covered, using Matlab and C#.
The measurements with the Hakki-Coleman method at IAE/IFI were validated at LOCEM/UFC. The development
of free-space method, together with TRL calibration was extensively studied and the validation was done together with
the DLR research group. In addition, GRL and LRL methods were also applied in the laboratory with the standard
materials for testing purposes.
The electromagnetic analysis of the prototype radome-antenna was done with the CST simulation software using
microstrip technology. Structural simulations were performed at the Mullite radome-antenna in C band for application
in SARA low orbit satellite to aid the optimum radome thickness parameter.
The complete experimental electromagnetic characterization was performed, involving the radiation pattern, gain
and impedance. These results agree satisfactorily with the CST simulations results.
Additionally to the technical results achieved during the project development, a free-space materials measurement
facility was developed and deployed at IFI facilities. This laboratory is pioneer in Brazil and complements IFI existent
facilities such as anechoic and reverberant chamber. It enables the characterization of different planar dielectric,
magnetic or absorbers materials. Finally, the project in its multidisciplinary approach provides integration and
qualification of human resources between different research groups in Brazil.
Acknowledgment
The work presented in this paper has been supported by National Counsel of Technological and Scientific
Development (CNPq Project no. 559991/2010-0). Special thanks to Stefan Thurner for providing experimental data on
free space measurements at DLR. The authors want to acknowledge the collaboration of Sgt. Bruno Duarte, João Paulo
Hasmann and Cláudio Nogueira from IAE/DCTA.
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