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A temperature is one of the parameters that have a great effect on the performance of microstrip antennas for TM 10 mode at 2.4 GHz frequency range. The effect of temperature on a resonance frequency, input impedance, voltage standing wave ratio, and return loss on the performance of a cylindrical microstrip printed antenna is studied in this paper. The effect of temperature on electric and magnetic fields are also studied. Three different substrate materials RT/duroid-5880 PTFE, K-6098 Teflon/Glass, and Epsilam-10 ceramic-filled Teflon are used for verifying the new model. KEYWORDS Temperature, Voltage Standing Wave Ratio VSWR, Return loss S11, effective dielectric constant, Transverse Magnetic TM 10 model.
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International Journal of Next-Generation Networks (IJNGN) Vol.3, No.3, September 2011
DOI : 10.5121/ijngn.2011.3301 1
The Performance of a Cylindrical Microstrip
Printed Antenna for
TM
10
Mode as a Function of
Temperature for Different Substrates
A. Elrashidi *, K. Elleithy
* and Hassan Bajwa†
*Department of Computer and Electrical Engineering
† Department of Electrical Engineering
University of Bridgeport, 221 University Ave,
Bridgeport, CT, USA
aelrashi@Bridgeport.edu
A
BSTRACT
A temperature is one of the parameters that have a great effect on the performance of microstrip antennas
for TM
10
mode at 2.4 GHz frequency range. The effect of temperature on a resonance frequency, input
impedance, voltage standing wave ratio, and return loss on the performance of a cylindrical microstrip
printed antenna is studied in this paper. The effect of temperature on electric and magnetic fields are also
studied. Three different substrate materials RT/duroid-5880 PTFE, K-6098 Teflon/Glass, and Epsilam-10
ceramic-filled Teflon are used for verifying the new model.
K
EYWORDS
Temperature, Voltage Standing Wave Ratio VSWR, Return loss S11, effective dielectric constant,
Transverse Magnetic TM
10
model.
1. I
NTRODUCTION
Due to unprinted growth in wireless applications and increasing demand of low cost solutions for
RF and microwave communication systems, the microstrip flat antenna, has undergone
tremendous growth recently. Though the models to analyze microstrip structures have been
widely accepted, effect of curvature on dielectric constant and antenna performance has not been
studied in detail. Low profile, low weight, low cost and its ability of conforming to curve surfaces
[1], conformal microstrip structures have also witnessed enormous growth in the past few years.
Applications of microstrip structures include Unmanned Aerial Vehicle (UAV), planes, rocket,
radars and communication industry [2]. Some advantages of conformal antennas over the planer
microstrip structure include, easy installation (randome not needed), capability of embedded
structure within composite aerodynamic surfaces, better angular coverage and controlled gain,
depending upon shape [3, 4]. While Conformal Antenna provide potential solution for many
applications it has some drawbacks due to bedding [5], those drawbacks include phase,
impedance, and resonance frequency errors due to the stretching and compression of the
dielectric material along the inner and outer surfaces of conformal surface. Changes in the
International Journal of Next-Generation Networks (IJNGN) Vol.3, No.3, September 2011
2
dielectric constant and material thickness also affect the performance of the antenna. Analysis
tools for conformal arrays are not mature and fully developed [6]. Dielectric materials suffer from
cracking due to bending and that will affect the performance of the conformal microstrip antenna.
In some applications, a microstrip antenna is required to operate in an environment that is close to
what is defined as room or standard conditions [7]-[11]. However, antennas often have to work in
harsh environments characterized by large temperature variations [12]. In this case, the substrate
properties suffer from some variations. The effect of that variation on the overall performance of
a microstrip conformal antenna is very important to study under a wide range of temperature.
2.
B
ACKGROUND
Conventional microstrip antenna has a metallic patch printed on a thin, grounded dielectric
substrate. Although patch can be of any shape rectangular patches, as shown in Figure 1 [13], are
preferred due to easy calculation and modeling.
Figure. 1. Rectangular microstrip antenna
Fringing field has a great effect on the performance of a microstrip antenna. In microstrip
antennas the electric field in the center of the patch is zero. The radiation is due to the fringing
field between the periphery of the patch and the ground plane. For rectangular patch shown in the
Figure 2, there is no field variation along the width and thickness. The amount of fringing field is
a function of the dimensions of the patch and the height of the substrate. Higher the substrate the
more is the fringe fields.
Due to effect of fringing a microstrip patch antenna would look electrically wider compared to its
physical dimensions. As shown in Figure 2, waves travel both in substrate and air. Thus an
effective dielectric constant ε
reff
is to be introduced. The effective dielectric constant ε
reff
take in
account both the fringing and the wave propagation in the line.
Figure 2. electric field lines (Side View).
The expression for the effective dielectric constant is introduced by A. Balanis [13], as shown in
Equation 1.
(1)
h
L
W
r
International Journal of Next-Generation Networks (IJNGN) Vol.3, No.3, September 2011
3
x
L
ε
r
R
z
The length of the patch is extended on each end by L is a function of effective dielectric
constant and the width to height ratio (W/h). L can be calculated according to a practical
approximate relation for the normalized extension of the length [14], as in Equation 2.
(2)
The effective length of the patch is L
eff
and can be calculated as in Equation 3.
L
eff
= L+2L (3)
By using the effective dielectric constant (Equation 1) and effective length (Equation 3), we can
calculate the resonance frequency of the antenna f
r
and all the microstrip antenna parameters.
Figure. 3. Physical and effective lengths of rectangular microstrip patch.
Cylindrical-Rectangular Patch Antenna
All the previous work for a conformal rectangular microstrip antenna assumed that, the curvature
does not affect the effective dielectric constant and the extension on the length. Effect of
curvature on the resonant frequency has been presented previously [15]. In this paper we present
the effect of fringing field on the performance of a conformal patch antenna. A mathematical
model that includes the effect of curvature on fringing filed and on antenna performance is
presented. The cylindrical-rectangular patch is the most famous and popular conformal antenna.
The manufacturing of this antenna is easy with respect to spherical and conical antennas.
Figurer 4: Geometry of cylindrical-rectangular patch antenna
W
L
L
L
International Journal of Next-Generation Networks (IJNGN) Vol.3, No.3, September 2011
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Effect of curvature of conformal antenna on resonant frequency been presented by Clifford M.
Krowne [15] as:
(4)
Where 2b is a length of the patch antenna, a is a radius of the cylinder, 2θ is the angle bounded
the width of the patch, ε represents electric permittivity and µ is the magnetic permeability as
shown in Figure 4.
3. T
EFLON AS A
S
UBSTRATE IN
M
ICROSTRIP
P
RINTED
A
NTENNAS
T. Seki et.al. introduced a highly efficient multilayer parasitic microstrip antenna array that is
constructed on a multilayer Teflon substrate for millimeter-wave system [16]. This antenna
achieves a radiation efficiency of greater than 91% and an associated antenna gain 11.1 dBi at 60
GHz. The antenna size is only 10 mm × 10 mm. So, using Teflon as a substrate material in
microstrip antennas is highly recommended nowadays, especially in conformal microstrip
antennas for its ability to bend over any surface [17].
4.
E
FFECT OF
T
EMPERATURE ON A
T
EFLON
S
UBSTRATE
P. Kabacik et.al. studied the effect of temperature on substrate parameters and their effect on
microstrip antenna performance [18]. Dielectric constant and dispersion factor are plotted as a
function of temperature for a wide temperature ranges equivalent to those in airborne
applications. The authors used Teflon-glass and ceramic-Teflon materials as a substrate for
microstrip antenna. Also, the authors conclude that, the measured dielectric constant value was
greater than the one specified in the data sheets.
The effect of temperature on Teflon material on the electrical properties is studied by A.
Hammoud et.al. [19]. In this work, the authors indicated that the dielectric properties of Teflon is
temperature dependence as illustrated in the next chapter.
The effect of high temperature on a Teflon substrate material on electrical properties, dielectric
constant, mechanical properties, and thermal properties are also studied [20] - [23].
5. T
EMPERATURE
E
FFECT ON THE
A
NTENNA
P
ERFORMANCE
For a microstrip antenna fixed on a projectile that fly at a long distance, the temperature will be
an issue for the performance of that antenna. A large variation of temperature (-25
0
C, 25
0
C and
75
0
C) will be considered during the studying. The effect of the temperature on the substrate
material of the microstrip antenna is studied in this paper [24].
The Temperature affects the dielectric constant of the substrate and also affects expansion of the
material which increase or decrease the volume of the dielectric with increasing or decreasing the
temperature [25]. The recorded dielectric constant of the Teflon at low frequencies is 2.07 at
room temperature but due to the dependency of the dielectric constant on the operating frequency
[26], the dielectric constant decreases to be around 2.02 at the range of Giga hertz.
International Journal of Next-Generation Networks (IJNGN) Vol.3, No.3, September 2011
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The measured relationship between temperature and dielectric constant is given in [26] as shown
in the Figure 3 as an actual data, and the fitted data that we already did using MATLAB software,
as a linear relation, is also shown bellow.
The linear Equation for that relation is illustrated in the following Equation:
(5)
Linear thermal expansion can be calculated as in the following formula [25]:
(6)
where: L
thermal
is the expansion in length.
L is the original length at certain temperature.
α is the coefficient of thermal expansion.
T is the difference of temperature.
So, the linear thermal expansion which is represents the ratio between L
thermal
and L is given by
[26], which is shown in Figure 4. The actual and fitted curves and the fitted Equation are given
bellow:
(7)
Figure 3. Dielectric constant vs. temperature for Teflon substrate at the range of GHz.
Hence, we can calculate the effect of temperature on the expansion of the dimensions of the
substrate and on the dielectric constant of the microstrip antenna. The new length or width of the
microstrip antenna will be due to the effect of fringing field and thermal expansion, so the new
length or width will take the form of Equation (8):
(8)
Also, the effect of fringing field and temperature on the dielectric constant of the substrate will be
considered in the calculations of antenna parameters.
International Journal of Next-Generation Networks (IJNGN) Vol.3, No.3, September 2011
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Figure 4. Linear thermal expansion vs. temperature for Teflon substrate.
6. R
ESULTS
For a range of GHz, the dominant mode is TM
10
for h<<W which is the case. Also, for the
antenna operates at the range of 2.4 GHz we can get the following dimensions; the original length
is 41.5 mm, the width is 50 mm, substrate height is 0.8 mm and for different lossy substrate we
can get the effect of curvature on the effective dielectric constant and the resonance frequency.
Three different substrate materials RT/duroid-5880 PTFE, K-6098 Teflon/Glass, and Epsilam-10
ceramic-filled Teflon are used for verifying the new algorithm. The dielectric constants for the
used materials are 2.07, 2.5 and 10 respectively with a tangent loss 0.0015, 0.002 and 0.0004
respectively.
The relation between the effective dielectric constant and radius of curvature for different values
of temperature, -25, 25 and 75
0
C is shown in Figure 5.
The relation between curvature and effective dielectric constant was introduced in [27], and by
using the generated model in [27] we can caudate the input impedance, VSWR and return loss.
6.1
RT/duroid-5880 PTFE substrate
Resonance frequency for TM
10
mode is shown in Figure 5. Due to temperature, decreasing in
resonance frequency for every 50
0
C in temperature is almost 40 MHz at radius of curvature 50
mm.
The real and imaginary parts of input impedance are shown in Figure 6 and 7 consequently. The
peak value of input impedance for a real part is 1800 which is higher than the values of TM
01
mode by 800 .
VSWR is given in Figure 8, and gives a minimum value around 4 which is higher than the value
from TM
01
mode. Return loss is around -12 dB, as in Figure 9, which is higher than the value
from TM
01
mode by -10 dB. So, one can note that, better performance can be obtained in case of
TM
01
mode than in case of TM
10
mode, lower return loss and lower VSWR.
The effect of temperature is almost the same for TM
01
and TM
10
modes in normalized electric and
magnetic fields. The effect of temperature is given in Figures 10 and 11 for normalized electric
and magnetic fields respectively.
International Journal of Next-Generation Networks (IJNGN) Vol.3, No.3, September 2011
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Increasing temperature increases the angle of radiation of the radiation pattern for electric and
magnetic fields by very small amount for a large value of temperature from -25
0
C to 150
0
C.
Figure 5. Resonance frequency versus radius of curvature for cylindrical-rectangular
and flat microstrip printed antenna at different temperatures 75, 25 and -25
0
C.
Figure 6. Real part of the input impedance as a function of frequency at different
temperatures 75, 27 and -25
0
C and radius of curvature 50 mm.
Figure 7. Imaginary part of the input impedance as a function of frequency at
different temperatures 75, 27 and -25
0
C and radius of curvature 50 mm.
International Journal of Next-Generation Networks (IJNGN) Vol.3, No.3, September 2011
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Figure 8. VSWR versus frequency at different temperatures 75, 27 and -25
0
C and
radius of curvature 50 mm.
Figure 9. Return loss (S11) as a function of frequency at different temperatures 75, 27
and -25
0
C and radius of curvature 50 mm.
Figure 10. Normalized electric field for different temperatures 150, 75, 27 and -25
0
C
at θ=0:2π and φ=0
0
and radius of curvature 50 mm
.
International Journal of Next-Generation Networks (IJNGN) Vol.3, No.3, September 2011
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Figure 11. Normalized magnetic field for different temperatures 150, 75, 27
and -25
0
C at θ=0:2π and φ=0
0
and radius of curvature 50 mm.
6.2 K-6098 Teflon/Glass substrate
Effect of temperature on a performance of K-6098 Teflon/Glass material is studied in this section.
The effect of temperature on the effective dielectric constant is shown in [23]. Using Figure 12,
we can note that, increasing in temperature leads to increasing in the value of effective dielectric
constant by 0.0007 for each Celsius degree.
Effective dielectric constant increases with increasing the temperature due to two reasons:
1. Increasing temperature leads to increasing the collision between atoms and electrons inside
the material and hence the speed of light inside the material will decrease which leads to
increases the effective dielectric constant.
2. Increasing temperature expands the dielectric material and hence, the distance which electric
field goes inside the substrate increases which means, the effective dielectric constant
increases.
Resonance frequency for TM
10
is shown in Figure 12. AS clearly notice from the Figure the
resonance frequency decreases by 30 MHz for increasing in temperature b 50
0
C. The peak value
of real part of input impedance is higher than in case of TM
01
mode by 300 as shown in Figure
13. Imaginary part is also given in Figure 14.
The value of VSWR is between 2 and 3 as shown in Figure 15 and the value of return loss is
almost -21 dB as shown in Figure 16.
Normalized electric and magnetic fields are shown in Figures 17 and 18 respectively. The same
results are almost obtained as in case of TM
01
mode, small change in radiation patterns due to
temperature change.
International Journal of Next-Generation Networks (IJNGN) Vol.3, No.3, September 2011
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Figure 12. Resonance frequency versus radius of curvature for cylindrical-rectangular
and flat microstrip printed antenna at different temperatures 75, 25 and -25
0
C.
Figure 13. Real part of the input impedance as a function of frequency at different
temperatures 75, 27 and -25
0
C and radius of curvature 50 mm.
Figure 14. Imaginary part of the input impedance as a function of frequency at
different temperatures 75, 27 and -25
0
C and radius of curvature 50 mm.
International Journal of Next-Generation Networks (IJNGN) Vol.3, No.3, September 2011
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Figure 15. VSWR versus frequency at different temperatures 75, 27 and -25
0
C and
radius of curvature 50 mm.
Figure 16. Return loss (S11) as a function of frequency at different temperatures 75, 27
and -25
0
C and radius of curvature 50 mm.
Figure 17. Normalized electric field for different temperatures 150, 75, 27 and -25
0
C.
at θ=0:2π and φ=0
0
and radius of curvature 50 mm.
International Journal of Next-Generation Networks (IJNGN) Vol.3, No.3, September 2011
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Figure 18. Normalized magnetic field for different temperatures 150, 75, 27 and -25
0
C.
at θ=0:2π and φ=0
0
and radius of curvature 50 mm.
6.3 Epsilam-10 ceramic-filled Teflon substrate
For Epsilam-10 ceramic-filled Teflon substrate; the same parameters are also studied in this
section. Due to temperature, the effective dielectric constant increases by 0.00068 for increasing
temperature by one Celsius degree. This value is less than the other two substrates, which is
0.0007 for K-6098 Teflon/Glass and 0.00074 for RT/duroid-5880 PTFE substrate. Hence; we can
conclude that, as the dielectric constant increases, the effect of temperature on the effective value
of dielectric constant decreases.
The resonance frequency for TM
10
mode is shown in Figure 19. The difference between
resonance frequencies due to increasing in temperature by 50
0
C is almost 10 MHz. The effect of
temperature on the real and imaginary parts of input impedance is not as in case of using
substrates of lower dielectric constants. As shown in Figures 20 and 21 respectively, the peak
value is less than in case of TM
01
mode by almost 150 for real and imaginary parts of input
impedance. VSWR and Return loss are shown in Figures 22 and 23 consequently. As in the
previous substrates, the performance in case of TM
01
is better than in case of TM
10
.
Normalized electric and magnetic fields are shown in Figures 24 and 25. As shown in the Figures,
the effect of temperature is very small in case of using substrates have high dielectric constant. In
both transverse magnetic modes and for high range of temperatures, the effect is almost vanishing
for both electric and magnetic fields radiation patterns.
International Journal of Next-Generation Networks (IJNGN) Vol.3, No.3, September 2011
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Figure 19. Resonance frequency versus radius of curvature for cylindrical-rectangular
and flat microstrip printed antenna at different temperatures 75, 25 and -25
0
C.
Figure 20. Real part of the input impedance as a function of frequency at different
temperatures 75, 27 and -25
0
C and radius of curvature 50 mm.
Figure 21. Imaginary part of the input impedance as a function of frequency
at different temperatures 75, 27 and -25
0
C and radius of curvature 50 mm.
International Journal of Next-Generation Networks (IJNGN) Vol.3, No.3, September 2011
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Figure 22. VSWR versus frequency at different temperatures 75, 27 and -25
0
C and
radius of curvature 50 mm.
Figure 23. Return loss (S11) as a function of frequency at different temperatures 75, 27
and -25
0
C and radius of curvature 50 mm.
Figure 24. Normalized electric field for different temperatures 150, 75, 27 and -25
0
C.
at θ=0:2π and φ=0
0
and radius of curvature 50 mm.
International Journal of Next-Generation Networks (IJNGN) Vol.3, No.3, September 2011
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Figure 25. Normalized magnetic field for different temperatures 150, 75, 27 and -25
0
C.
at θ=0:2π and φ=0
0
and radius of curvature 50 mm.
7. C
ONCLUSION
The effect of temperature on the performance of a conformal microstrip printed antenna used for
a projectile flight on a high distance is very important to study. The temperature affects the three
different substrates effective dielectric constant and hence affect the operating resonance
frequency for TM
10
mode. The effect of temperature on input impedance, VSWR and return loss
are also studied for a radius of curvature of 50 mm. We notice that, as the temperature increases,
the effective dielectric constant is also increases for different materials used. On the other hand,
the resonance frequency decreases with increasing temperature. VSWR and return loss are
decreasing as the temperature increases.
The change in resonance frequency is between 40 MHz for TM
10
mode. This shift is very small
for a wide range of temperature used, but it is very effective in case of using frequency hopping
technique.
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Accepted
Authors
Ali Elrshidi, Ali is Ph.D student in University of Bridgeport. Ali received the Bachelor in
communication engineering from the University of Alexandria, Egypt 2002. He got his
master degree in fiber optics field in 2006 from the same university under supervision of
Prof: Ali Okaz, Prof. Moustafa Hussien, and Dr: Keshk. He works in a project funded by
US Army, to control the motion of a small projectile using two small stepper motors. Also,
Ali has designed a microstip printed antenna works at 2.4 GHz and gives a high
performance.
Dr. Elleithy is the Associate Dean for Graduate Studies in the School of Engineering at the
University of Bridgeport. He has research interests are in the areas of network security,
mobile communications, and formal approaches for design and verification. He has
published more than one hundred fifty research papers in international journals and
conferences in his areas of expertise. Dr. Elleithy is the co-chair of the International Joint
Conferences on Computer, Information, and Systems Sciences, and Engineering (CISSE).
CISSE is the first Engineering/Computing and Systems Research E-Conference in the world to be
completely conducted online in real-time via the internet and was successfully running for four years.Dr.
Elleithy is the editor or co-editor of 10 books published by Springer for advances on Innovations and
Advanced Techniques in Systems, Computing Sciences and Software.
Dr. Elleithy received the B.Sc. degree in computer science and automatic control from Alexandria
University in 1983, the MS Degree in computer networks from the same university in 1986, and the MS
and Ph.D. degrees in computer science from The Center for Advanced Computer Studies at the University
of Louisiana at Lafayette in 1988 and 1990.
International Journal of Next-Generation Networks (IJNGN) Vol.3, No.3, September 2011
18
Hassan Bajwa, Ph.D., is an Assistant Professor of Electrical Engineering at The
University of Bridgeport. He received his BSc degree in Electrical Engineering from
Polytechnic University of New York in 1998. From 1998 to 2001 he worked for
Software Spectrum and IT Factory Inc, NY. He received his MS from the City College
of New York in 2003, and his Doctorate in Electrical Engineering from City University
of New York in 2007. Dr. Hassan research interests include low power sensor networks,
flexible electronics, RF circuit design, Antennas, reconfigurable architecture, bio-
electronics, and low power implantable devices. He is also working on developing
biomedical instruments and computation tools for bioinformatics.
... The effect of curvature on a fringing field and on the resonance frequency of the microstrip printed antenna is studied in [19]. Also, the effect of curvature on the performance of a microstrip antenna as a function of temperature for TM 01 and TM 10 is introduced in [21], [21]. ...
... The effect of curvature on a fringing field and on the resonance frequency of the microstrip printed antenna is studied in [19]. Also, the effect of curvature on the performance of a microstrip antenna as a function of temperature for TM 01 and TM 10 is introduced in [21], [21]. ...
... By using Equations (15) and (18), we can get Equation (21) for Z 21 as follow: (21) and by substituting in Equation (18), the mutual coupling coefficient can be calculated. ...
Chapter
Full-text available
Curvature has a great effect on fringing field of a microstrip antenna. Consequently, the fringing field affects the effective dielectric constant and then all antenna parameters. A new mathematical model for return loss mutual coupling coefficient as a function of curvature for two element array antenna is introduced in this paper. These parameters are given for TM10 mode and using three different substrate materials RT/duroid-5880 PTFE, K-6098 Teflon/Glass and Epsilam-10 ceramic-filled Teflon. Index Terms— Fringing field, Curvature, effective dielectric constant and Return loss (S11), mutual coupling coefficient (S12), Transverse Magnetic TM 10 mode
... To overcome above limitations, various attempts have been made recently to make an antenna insensitive to changing environment. Adding a superstrate layer over patch antennas or by placing the antenna under plastic covers is one of the solutions for protecting the antenna from environmental hazards like moisture and temperature [4]. Numerous superstrates and their configurations were reported by the various researchers in the literature to improve the antenna performance. ...
... Further to enhance the bandwidth, the ground defects are introduced. The geometry of the patch antenna is shown in figure 5. 1 4 mm w 2 20 mm l 2 4 mm w 3 4.1 mm l 3 4 mm w 4 3.1 mm ...
Article
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For the protection of antenna from external environmental conditions, there is a need that antenna should be covered with a stable, non-reactive, highly durable and weather resistive material which is insensitive to changing external environment. Hence, in this paper silicone rubber is proposed as a superstrate layer for patch antenna for its protection. The electrical properties of silicon rubber sealant are experimentally found out and its effect of using as superstrate on coaxial fed microstrip patch antenna using transmission line model is observed. The overall performance is degraded by slightly after the use of superstrate. Further to improve the performance of superstrate loaded antenna, patch slots and ground defects have been proposed. The proposed design achieves the wideband of 790 MHz (13.59 %), gain of 7.12 dB, VSWR of 1.12 and efficiency of 83.02 %.
... The effect of curvature on a fringing field and on the resonance frequency of the microstrip printed antenna is studied in [15]. Also, the effect of curvature on the performance of a microstrip antenna as a function of temperature for TM 01 and TM 10 is introduced in [16], [17]. ...
... (16) By using Equations (6), (11), (14), (16) and substitute in (15), we can obtain the input impedance for a rectangular microstrip antenna conformal in a cylindrical body as in the following Equation: (17) ...
Article
Full-text available
Curvature has a great effect on fringing field of a microstrip antenna and consequently fringing field affects effective dielectric constant and then all antenna parameters. A new mathematical model for input impedance, return loss and voltage standing wave ratio is introduced in this paper. These parameters are given for TM 10 mode and using two dif-ferent substrate materials K-6098 Teflon/Glass and Epsilam-10 Ceramic-Filled Teflon materials. Keywords Fringing field, Curvature, effective dielectric constant and Return loss (S11), Voltage Standing Wave Ratio (VSWR), Transverse Magnetic TM 10 mode.
... The effect of curvature on a fringing field and on the resonance frequency of the microstrip printed antenna is studied in [15]. Also, the effect of curvature on the performance of a microstrip antenna as a function of temperature for TM 01 and TM 10 is introduced in [16], [17]. III. ...
Article
Full-text available
Curvature has a great effect on fringing field of a microstrip antenna and consequently fringing field affects effective dielectric constant and then all antenna parameters. A new mathematical model for input impedance, return loss, voltage standing wave ratio and electric and magnetic fields is introduced in this paper. These parameters are given for TM 01 mode and using two different substrate materials RT/duroid-5880 PTFE and K-6098 Teflon/Glass. Experimental results for RT/duroid-5880 PTFE substrate are also introduced to validate the new model. Keywords: Fringing field, Curvature, effective dielectric constant and Return loss (S11), Voltage Standing Wave Ratio (VSWR), Transverse Magnetic TM 01 mode.
... The effect of curvature on a fringing field and on the resonance frequency of the microstrip printed antenna is studied in [15]. Also, the effect of curvature on the performance of a microstrip antenna as a function of temperature for TM 01 and TM 10 is introduced in [16,17]. ...
Article
Full-text available
Curvature has a great effect on fringing field of a microstrip antenna and consequently fringing field affects effective dielectric constant and then all antenna parameters. A new mathematical model for input impedance, return loss and voltage standing wave ratio is introduced in this paper. These parameters are given for TM 01 mode and using two dif-ferent substrate materials K-6098 Teflon/Glass and Epsilam-10 Ceramic-Filled Teflon materials.
Article
Full-text available
A novel hypothesis is proposed for the radiation pattern of a Rec-tangular Microstrip Patch Antenna sensitive to temperature variations from the ideal room temperature tolerance under which it was manufactured. In order to validate this hypothetical model, equations relating the resonating frequency, patch length and dielectric constant of the antenna to variations from the room temperature were improved. Simulations were carried out to validate the hypoth-esis in the drifts in ambient temperature effects on dimensions of the patch an-tenna and its field radiation patterns; including its directivity, power pattern, max-imum radiation in the electric-field plane.
Article
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This paper describes the effect of temperature vari ation on microstrip patch antenna for different sub strate materials. Eight materials are chosen as substrate and the effect of temperature variation is studied on each substrate material. A technique of temperature compensation has also be en developed with substrate height variation. It is also seen that the change in resonance frequency due to variation of t emperature can be compensated by varying the height of the substrate. The proposed antenna is designed and simulated by u sing HFSS software.
Article
Full-text available
The fringing field has an important effect on the accurate theoretical modeling and performance analysis of microstrip patch antennas. Though, fringing fields effects on the performance of antenna and its resonant frequency have been presented before, effects of curvature on fringing field have not been reported before. The effective dielectric constant is calculated using a conformal mapping technique for a conformal substrate printed on a cylindrical body. Furthermore, the effect of effective dielectric constant on the resonance frequency of the conformal microstrip antenna is also studied. Experimental results are compared to the analytical results for RT/duroid-5880 PTFE substrate material. Three different substrate materials RT/duroid-5880 PTFE, K-6098 Teflon/Glass, and Epsilam-10 ceramic-filled Teflon are used for verifying the new model. KEYWORDS Fringing field, microstrip antenna, effective dielectric constant and Resonance frequency.
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This reference guide brings together a wide range of critical data on the effect of temperature on plastics and elastomers, enabling engineers to make optimal material choices and design decisions. The effects of humidity level and strain rate on mechanical and electrical properties are also covered. The data are supported by explanations of how to make use of the data in real world engineering contexts. High (and low) temperatures can have a significant impact on plastics processing and applications, particularly in industries such as automotive, aerospace, oil and gas, packaging, and medical devices, where metals are increasingly being replaced by plastics. Additional plastics have also been included for polyesters, polyamides and others where available, including polyolefins, elastomers and fluoropolymers. Entirely new sections on biodegradable polymers and thermosets have been added to the book. The level of data included - along with the large number of graphs and tables for easy comparison - saves readers the need to contact suppliers, and the selection guide has been fully updated, giving assistance on the questions which engineers should be asking when specifying materials for any given application.
Chapter
IntroductionThe ProblemElectrically Small SurfacesElectrically Large SurfacesTwo ExamplesA Comparison of Analysis Methods Appendix 4A—Interpretation of the ray theoryReferences
Article
A novel antenna structure formed by combining the Yagi-Uda array concept and the microstrip radiator technique is discussed. This antenna, called the microstrip Yagi array, has been developed for the mobile satellite (MSAT) system as a low-profile, low-cost, and mechanically steered medium-gain land-vehicle antenna. With the antenna's active patches (driven elements) and parasitic patches (refl 5a8 ector and director elements) located on the same horizontal plane, the main beam of the array can be tilted, by the effect of mutual coupling, in the elevation direction providing optimal coverage for users in the continental United States. Because the parasitic patches are not connected to any of the lossy RF power distributing circuit the antenna is an efficient radiating system. With the complete monopulse beamforming and power distributing circuits etched on a single thin stripline board underneath the microstrip Yagi array, the overall L -band antenna system has achieved a very low profile for vehicle rooftop mounting, as well as a low manufacturing cost. Experimental results demonstrate the performance of this antenna
Article
It is recognized that, with progressive increases in the working temperature of gas turbines, metallic alloys may no longer be adequate for rotor or stator blading. The use of more refractory but more brittie materials, i.e., ceramics and ceramic-metal mixtures (cermets) was suggested. An evaluation is given of the major properties involved, viz. creep strength, fatigue strength, resistance to thermal fatigue (i.e., to repeated thermal shocks), oxidation- resistance, and impact-resistance. The materials evaluated include oxides, oxide- metal cermets, carbides, carbide-metal cermets, molybdenum disilicide, and silicon nitride. The equipment for determining the effects of alternating and steady mechanical stresses to 1200 deg C is described. The relative merits of the test materials are discussed. It is concluded that the resistance to thermal fatigue and to impact of the ceramics and cermets is inferior to that of metallic alloys in current use. (auth)
Chapter
In this chapter we describe the characteristics of cylindrical microstrip antennas excited by a coax feed or through a coupling slot fed by a microstrip feed line. Typical types of rectangular, triangular, circular, and annular-ring microstrip antennas are analyzed. Characterization of curvature effects on the input impedance and radiation characteristics is of major concern. Calculated solutions obtained from various theoretical techniques, such as the full-wave approach, cavity-model analysis, and the generalized transmission-line model (GTLM) theory, are shown and discussed. Some experimental results are also presented for comparison.
Article
A novel antenna structure formed by combining the Yagi-Uda array concept and the microstrip radiator technique is discussed. This antenna, called the microstrip Yagi array, has been developed for the mobile satellite (MSAT) system as a low-profile, low-cost, and mechanically steered medium-gain land-vehicle antenna. With the antenna's active patches (driven elements) and parasitic patches (reflector and director elements) located on the same horizontal plane, the main beam of the array can be tilted, by the effect of mutual coupling, in the elevation direction providing optimal coverage for users in the continental United States. Because the parasitic patches are not connected to any of the lossy RF power distributing circuit the antenna is an efficient radiating system. With the complete monopulse beamforming and power distributing circuits etched on a single thin stripline board underneath the microstrip Yagi array, the overall L-band antenna system has achieved a very low profile for vehicle's rooftop mounting, as well as a low manufacturing cost. Experimental results demonstrate the performance of this antenna.
Book
This publication is the first comprehensive treatment of conformal antenna arrays from an engineering perspective. There are journal and conference papers that treat the field of conformal antenna arrays, but they are typically theoretical in nature. While providing a thorough foundation in theory, the authors of this publication provide readers with a wealth of hands-on instruction for practical analysis and design of conformal antenna arrays. Thus, readers gain the knowledge they need, alongside the practical know-how to design antennas that are integrated into structures such as an aircraft or a skyscraper. Compared to planar arrays, conformal antennas, which are designed to mold to curved and irregularly shaped surfaces, introduce a new set of problems and challenges. To meet these challenges, the authors provide readers with a thorough understanding of the nature of these antennas and their properties. Then, they set forth the different methods that must be mastered to effectively handle conformal antennas. This publication goes well beyond some of the common issues dealt with in conformal antenna array design into areas that include: Mutual coupling among radiating elements and its effect on the conformal antenna array characteristics Doubly curved surfaces and dielectric covered surfaces that are handled with a high frequency method Explicit formulas for geodesics on surfaces that are more general than the canonical circular cylinder and sphere With specific examples of conformal antenna designs, accompanied by detailed illustrations and photographs, this is a must-have reference for engineers involved in the design and development of conformal antenna arrays. The publication also serves as a text for graduate courses in advanced antennas and antenna systems.
Conference Paper
The conformal FDTD algorithm is employed to analyze the characteristics of the probe-fed conically conformal microstrip patch antenna. The non-uniform meshing technique in Cartesian coordinate system is used. The numerical results show that the conformal algorithm is efficient and accurate enough, besides its better adaptability in dealing with arbitrary antenna structures and shapes.
Conference Paper
This paper proposes a high efficiency multi-layer parasitic microstrip array antenna that is constructed on a multi-layer TEFLON substrate for millimeter-wave system-on-package modules. The design and performance of the proposed array antenna are described. The proposed antenna achieves the antenna gain of 11.1 dBi and its radiation efficiency is greater than 91%. This paper demonstrates a 60-GHz band prototype antenna employing a multi-layer TEFLON substrate that is well suited to achieving high gain and a wide bandwidth. The measured performance of the prototype antenna is also described.