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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
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International Journal of Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
DOI : 10.5121/ijcnc.2011.3501 1
EFFECT OF TEMPERATURE ON THE
PERFORMANCE OF A CYLINDRICAL MICROSTRIP
PRINTED ANTENNA FOR
TM
01
MODE USING
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
ABSTRACT
A temperature is one of the parameters that have a great effect on the performance of microstrip antennas
for TM01 mode. 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 for a microstrip antenna for its flexibility on cylindrical bodies.
KEYWORDS
Temperature, Voltage Standing Wave Ratio VSWR, Return loss S11, effective dielectric constant,
Transverse Magnetic TM01 model.
1. INTRODUCTION
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 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
International Journal of Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
2
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. BACKGROUND
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
ɛ
r
International Journal of Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
3
y
x
L
ε
r
z
The length of the patch is extended on each end by ΔL is a function of effective dielectric
constant and the width to height ratio (W/h). ΔL 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+2ΔL (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
ΔL
L
ΔL
International Journal of Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
4
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, 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. TEFLON AS A SUBSTRATE IN MICROSTRIP PRINTED ANTENNAS
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. EFFECT OF TEMPERATURE ON A TEFLON SUBSTRATE
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. TEMPERATURE EFFECT ON THE ANTENNA PERFORMANCE
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.
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.
International Journal of Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
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The linear Equation for that relation is illustrated in the following Equation:
= 0.00072 +
( ℃)
(5)
Linear thermal expansion can be calculated as in the following formula [25]:
= × × (6)
where: ΔL
thermal
is the expansion in length.
L is the original length at certain temperature.
α is the coefficient of thermal expansion.
ΔT is the difference of temperature.
So, the linear thermal expansion which is represents the ratio between ΔL
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:
= 7.2 × 10 + 3.5 × 10 + 0.013 0.26 (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 Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
5
The linear Equation for that relation is illustrated in the following Equation:
= 0.00072 +
( ℃)
(5)
Linear thermal expansion can be calculated as in the following formula [25]:
= × × (6)
where: ΔL
thermal
is the expansion in length.
L is the original length at certain temperature.
α is the coefficient of thermal expansion.
ΔT is the difference of temperature.
So, the linear thermal expansion which is represents the ratio between ΔL
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:
= 7.2 × 10 + 3.5 × 10 + 0.013 0.26 (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 Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
5
The linear Equation for that relation is illustrated in the following Equation:
= 0.00072 +
( ℃)
(5)
Linear thermal expansion can be calculated as in the following formula [25]:
= × × (6)
where: ΔL
thermal
is the expansion in length.
L is the original length at certain temperature.
α is the coefficient of thermal expansion.
ΔT is the difference of temperature.
So, the linear thermal expansion which is represents the ratio between ΔL
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:
= 7.2 × 10 + 3.5 × 10 + 0.013 0.26 (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 Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
6
Figure 4. Linear thermal expansion vs. temperature for Teflon substrate.
2. Results
For a range of GHz, the dominant mode is TM
01
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 7.
The relation between curvature and effective dielectric constant was introduced in [27], and by
using the generated model we can caudate the input impedance, VSWR and return loss.
a) RT/duroid-5880 PTFE substrate
Resonance frequency for TM
01
as a function of curvature with different values of temperatures
is introduced in Figure 8. The resonance frequency decreases with increasing temperature
because of inverse relation between effective dielectric constant and temperature. Due to
temperature, decreasing in resonance frequency for every 50
0
C in temperature is almost 20
MHz.
Real part of input impedance at 50 mm radius of curvature at different values of temperatures is
illustrated in Figure 9. As notice from the previous Figures, the resonance frequency decreases
with increasing temperature by 20 MHz for every 50
0
C. The same thing is also noted from
Figure 9, for every 50
0
C increasing in temperature, the resonance frequency is decreasing by
almost 20 MHz. The peak value is also increasing with increasing temperature by very small
values.
International Journal of Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
6
Figure 4. Linear thermal expansion vs. temperature for Teflon substrate.
2. Results
For a range of GHz, the dominant mode is TM
01
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 7.
The relation between curvature and effective dielectric constant was introduced in [27], and by
using the generated model we can caudate the input impedance, VSWR and return loss.
a) RT/duroid-5880 PTFE substrate
Resonance frequency for TM
01
as a function of curvature with different values of temperatures
is introduced in Figure 8. The resonance frequency decreases with increasing temperature
because of inverse relation between effective dielectric constant and temperature. Due to
temperature, decreasing in resonance frequency for every 50
0
C in temperature is almost 20
MHz.
Real part of input impedance at 50 mm radius of curvature at different values of temperatures is
illustrated in Figure 9. As notice from the previous Figures, the resonance frequency decreases
with increasing temperature by 20 MHz for every 50
0
C. The same thing is also noted from
Figure 9, for every 50
0
C increasing in temperature, the resonance frequency is decreasing by
almost 20 MHz. The peak value is also increasing with increasing temperature by very small
values.
International Journal of Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
6
Figure 4. Linear thermal expansion vs. temperature for Teflon substrate.
2. Results
For a range of GHz, the dominant mode is TM
01
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 7.
The relation between curvature and effective dielectric constant was introduced in [27], and by
using the generated model we can caudate the input impedance, VSWR and return loss.
a) RT/duroid-5880 PTFE substrate
Resonance frequency for TM
01
as a function of curvature with different values of temperatures
is introduced in Figure 8. The resonance frequency decreases with increasing temperature
because of inverse relation between effective dielectric constant and temperature. Due to
temperature, decreasing in resonance frequency for every 50
0
C in temperature is almost 20
MHz.
Real part of input impedance at 50 mm radius of curvature at different values of temperatures is
illustrated in Figure 9. As notice from the previous Figures, the resonance frequency decreases
with increasing temperature by 20 MHz for every 50
0
C. The same thing is also noted from
Figure 9, for every 50
0
C increasing in temperature, the resonance frequency is decreasing by
almost 20 MHz. The peak value is also increasing with increasing temperature by very small
values.
International Journal of Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
7
Figure 10 shows the effect of temperature on the imaginary part of input impedance which
gives the same results as a real part. Reactance equal to zero at the same value of frequency of a
peak value for a real part of input impedance, this frequency is called a resonance frequency.
VSWR and Return loss are shown in Figures 11 and 12 respectively for 50 mm radius of
curvature and temperatures -50, 27 and 75
0
C. We can easily notice that, decreasing in
temperature by 50
0
C leads to increasing in frequency for minimum values of VSWR and return
loss by 20 MHz. VSWR values are between 1 and 2 at the resonance frequencies also, return
losses are between -23 and -24 dB which is very efficient in the antenna manufacture process
and gives a good performance.
Normalized electric and magnetic fields as a function of temperature at 50 mm radius of
curvature and for different values of temperatures, -25, 27, 75 and 150
0
C, are shown bellow
in Figures 13 and 14 respectively. The effect of temperature for a wide range, from -25 to 150
0
C, in the electric field at the same value of frequency shows the effect of temperature is in the
range of 10% of the value. The same results are obtained in the normalized magnetic field
values as a function of temperature.
Hence, we can note that, the effect of temperature on radiation patterns is less than the effect of
curvature. So, the radiation pattern angle is almost the same and field strength is slightly
different in a range of 200
0
C.
Figure. 7. Effective dielectric constant versus radius of curvature for cylindrical-rectangular and a flat
microstrip printed antenna at different temperatures 75, 25 and -25
0
C.
International Journal of Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
7
Figure 10 shows the effect of temperature on the imaginary part of input impedance which
gives the same results as a real part. Reactance equal to zero at the same value of frequency of a
peak value for a real part of input impedance, this frequency is called a resonance frequency.
VSWR and Return loss are shown in Figures 11 and 12 respectively for 50 mm radius of
curvature and temperatures -50, 27 and 75
0
C. We can easily notice that, decreasing in
temperature by 50
0
C leads to increasing in frequency for minimum values of VSWR and return
loss by 20 MHz. VSWR values are between 1 and 2 at the resonance frequencies also, return
losses are between -23 and -24 dB which is very efficient in the antenna manufacture process
and gives a good performance.
Normalized electric and magnetic fields as a function of temperature at 50 mm radius of
curvature and for different values of temperatures, -25, 27, 75 and 150
0
C, are shown bellow
in Figures 13 and 14 respectively. The effect of temperature for a wide range, from -25 to 150
0
C, in the electric field at the same value of frequency shows the effect of temperature is in the
range of 10% of the value. The same results are obtained in the normalized magnetic field
values as a function of temperature.
Hence, we can note that, the effect of temperature on radiation patterns is less than the effect of
curvature. So, the radiation pattern angle is almost the same and field strength is slightly
different in a range of 200
0
C.
Figure. 7. Effective dielectric constant versus radius of curvature for cylindrical-rectangular and a flat
microstrip printed antenna at different temperatures 75, 25 and -25
0
C.
International Journal of Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
7
Figure 10 shows the effect of temperature on the imaginary part of input impedance which
gives the same results as a real part. Reactance equal to zero at the same value of frequency of a
peak value for a real part of input impedance, this frequency is called a resonance frequency.
VSWR and Return loss are shown in Figures 11 and 12 respectively for 50 mm radius of
curvature and temperatures -50, 27 and 75
0
C. We can easily notice that, decreasing in
temperature by 50
0
C leads to increasing in frequency for minimum values of VSWR and return
loss by 20 MHz. VSWR values are between 1 and 2 at the resonance frequencies also, return
losses are between -23 and -24 dB which is very efficient in the antenna manufacture process
and gives a good performance.
Normalized electric and magnetic fields as a function of temperature at 50 mm radius of
curvature and for different values of temperatures, -25, 27, 75 and 150
0
C, are shown bellow
in Figures 13 and 14 respectively. The effect of temperature for a wide range, from -25 to 150
0
C, in the electric field at the same value of frequency shows the effect of temperature is in the
range of 10% of the value. The same results are obtained in the normalized magnetic field
values as a function of temperature.
Hence, we can note that, the effect of temperature on radiation patterns is less than the effect of
curvature. So, the radiation pattern angle is almost the same and field strength is slightly
different in a range of 200
0
C.
Figure. 7. Effective dielectric constant versus radius of curvature for cylindrical-rectangular and a flat
microstrip printed antenna at different temperatures 75, 25 and -25
0
C.
International Journal of Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
8
Figure. 8. Resonance frequency versus radius of curvature for cylindrical-rectangular and a flat
microstrip printed antenna at different temperatures 75, 25 and -25
0
C.
Figure. 9. 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. 10. Imaginary part of the input impedance as a function of frequency at different temperatures 75,
25 and -25
0
C and radius of curvature 50 mm.
International Journal of Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
8
Figure. 8. Resonance frequency versus radius of curvature for cylindrical-rectangular and a flat
microstrip printed antenna at different temperatures 75, 25 and -25
0
C.
Figure. 9. 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. 10. Imaginary part of the input impedance as a function of frequency at different temperatures 75,
25 and -25
0
C and radius of curvature 50 mm.
International Journal of Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
8
Figure. 8. Resonance frequency versus radius of curvature for cylindrical-rectangular and a flat
microstrip printed antenna at different temperatures 75, 25 and -25
0
C.
Figure. 9. 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. 10. Imaginary part of the input impedance as a function of frequency at different temperatures 75,
25 and -25
0
C and radius of curvature 50 mm.
International Journal of Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
9
Figure. 11. VSWR versus frequency at different temperatures 75, 25 and -25
0
C and radius of curvature
50 mm.
Figure. 12. Return loss (S11) as a function of frequency at different temperatures 75, 25 and -25
0
C and
radius of curvature 50 mm.
Figure. 13. 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 Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
9
Figure. 11. VSWR versus frequency at different temperatures 75, 25 and -25
0
C and radius of curvature
50 mm.
Figure. 12. Return loss (S11) as a function of frequency at different temperatures 75, 25 and -25
0
C and
radius of curvature 50 mm.
Figure. 13. 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 Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
9
Figure. 11. VSWR versus frequency at different temperatures 75, 25 and -25
0
C and radius of curvature
50 mm.
Figure. 12. Return loss (S11) as a function of frequency at different temperatures 75, 25 and -25
0
C and
radius of curvature 50 mm.
Figure. 13. 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 Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
10
Figure. 14. 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.
b) 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 Figure 15.
Using Figure 15, 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 mode TM
01
as a function of curvature for different values of
temperatures is shown in Figure 16; resonance frequency decreases with increasing in
temperature, almost 15 MHz decreasing in resonance frequency for 50
0
C increasing in
temperature.
Peak values of a real part of input impedance are shifted to the left as shown in Figures 17 and
18 respectively, decreasing in frequency, with increasing in temperature. The difference
between peaks of real part of input impedance is almost 15 MHz due to change in temperature
by 50
0
C. The same scenario occurred in case of reactance, imaginary part of input impedance,
increasing temperature leads to shifting in imaginary part to left.
VSWR and return loss are shown in Figures 19 and 20 respectively. 15 MHz between
resonance frequencies for three different temperatures are simply notice in these Figures.
The effect of temperature on normalized electric and magnetic fields are given in Figures 21
and 22 respectively for a wide range of temperatures, -25, 27, 75 and 150
0
C, and for angle θ
International Journal of Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
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Figure. 14. 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.
b) 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 Figure 15.
Using Figure 15, 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 mode TM
01
as a function of curvature for different values of
temperatures is shown in Figure 16; resonance frequency decreases with increasing in
temperature, almost 15 MHz decreasing in resonance frequency for 50
0
C increasing in
temperature.
Peak values of a real part of input impedance are shifted to the left as shown in Figures 17 and
18 respectively, decreasing in frequency, with increasing in temperature. The difference
between peaks of real part of input impedance is almost 15 MHz due to change in temperature
by 50
0
C. The same scenario occurred in case of reactance, imaginary part of input impedance,
increasing temperature leads to shifting in imaginary part to left.
VSWR and return loss are shown in Figures 19 and 20 respectively. 15 MHz between
resonance frequencies for three different temperatures are simply notice in these Figures.
The effect of temperature on normalized electric and magnetic fields are given in Figures 21
and 22 respectively for a wide range of temperatures, -25, 27, 75 and 150
0
C, and for angle θ
International Journal of Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
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Figure. 14. 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.
b) 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 Figure 15.
Using Figure 15, 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 mode TM
01
as a function of curvature for different values of
temperatures is shown in Figure 16; resonance frequency decreases with increasing in
temperature, almost 15 MHz decreasing in resonance frequency for 50
0
C increasing in
temperature.
Peak values of a real part of input impedance are shifted to the left as shown in Figures 17 and
18 respectively, decreasing in frequency, with increasing in temperature. The difference
between peaks of real part of input impedance is almost 15 MHz due to change in temperature
by 50
0
C. The same scenario occurred in case of reactance, imaginary part of input impedance,
increasing temperature leads to shifting in imaginary part to left.
VSWR and return loss are shown in Figures 19 and 20 respectively. 15 MHz between
resonance frequencies for three different temperatures are simply notice in these Figures.
The effect of temperature on normalized electric and magnetic fields are given in Figures 21
and 22 respectively for a wide range of temperatures, -25, 27, 75 and 150
0
C, and for angle θ
International Journal of Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
11
from 0 to 2π and φ equal to zero. The effect of temperature for a wide range is not very big; it is
in a very small range from 90% to 100%.
Figure. 15. Effective dielectric constant versus radius of curvature for cylindrical-rectangular and flat
microstrip printed antenna at different temperatures 75, 25 and -25
0
C.
Figure. 16. Resonance frequency versus radius of curvature for cylindrical-rectangular and flat microstrip
printed antenna at different temperatures 75, 25 and -25
0
C.
Figure. 17. Real part of the input impedance as a function of frequency at different temperatures 75, 25
and -25
0
C and radius of curvature 50 mm.
International Journal of Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
11
from 0 to 2π and φ equal to zero. The effect of temperature for a wide range is not very big; it is
in a very small range from 90% to 100%.
Figure. 15. Effective dielectric constant versus radius of curvature for cylindrical-rectangular and flat
microstrip printed antenna at different temperatures 75, 25 and -25
0
C.
Figure. 16. Resonance frequency versus radius of curvature for cylindrical-rectangular and flat microstrip
printed antenna at different temperatures 75, 25 and -25
0
C.
Figure. 17. Real part of the input impedance as a function of frequency at different temperatures 75, 25
and -25
0
C and radius of curvature 50 mm.
International Journal of Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
11
from 0 to 2π and φ equal to zero. The effect of temperature for a wide range is not very big; it is
in a very small range from 90% to 100%.
Figure. 15. Effective dielectric constant versus radius of curvature for cylindrical-rectangular and flat
microstrip printed antenna at different temperatures 75, 25 and -25
0
C.
Figure. 16. Resonance frequency versus radius of curvature for cylindrical-rectangular and flat microstrip
printed antenna at different temperatures 75, 25 and -25
0
C.
Figure. 17. Real part of the input impedance as a function of frequency at different temperatures 75, 25
and -25
0
C and radius of curvature 50 mm.
International Journal of Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
12
Figure. 18. Imaginary part of the input impedance as a function of frequency at different temperatures 75,
25 and -25
0
C and radius of curvature 50 mm.
Figure. 19. VSWR versus frequency at different temperatures 75, 25 and -25
0
C and radius of curvature
50 mm.
Figure. 20. Return loss (S11) as a function of frequency at different temperatures 75, 25 and -25
0
C and
radius of curvature 50 mm.
International Journal of Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
12
Figure. 18. Imaginary part of the input impedance as a function of frequency at different temperatures 75,
25 and -25
0
C and radius of curvature 50 mm.
Figure. 19. VSWR versus frequency at different temperatures 75, 25 and -25
0
C and radius of curvature
50 mm.
Figure. 20. Return loss (S11) as a function of frequency at different temperatures 75, 25 and -25
0
C and
radius of curvature 50 mm.
International Journal of Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
12
Figure. 18. Imaginary part of the input impedance as a function of frequency at different temperatures 75,
25 and -25
0
C and radius of curvature 50 mm.
Figure. 19. VSWR versus frequency at different temperatures 75, 25 and -25
0
C and radius of curvature
50 mm.
Figure. 20. Return loss (S11) as a function of frequency at different temperatures 75, 25 and -25
0
C and
radius of curvature 50 mm.
International Journal of Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
13
Figure. 21. 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.
Figure. 22. 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.
c) 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 as shown in Figure 23. 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.
Figure 24 shows the resonance frequency as a function of curvature for different temperatures.
The difference between resonance frequencies due to increasing in temperature by 50
0
C is
almost 18 MHz.
The real part of input impedance is shown in Figure 25, the resonance value, resistance, of
input impedance at temperature 75
0
C is 0.959 GHz and 0.9608 GHz at temperature 27
0
C
which means, the difference is 18 MHz.
International Journal of Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
13
Figure. 21. 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.
Figure. 22. 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.
c) 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 as shown in Figure 23. 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.
Figure 24 shows the resonance frequency as a function of curvature for different temperatures.
The difference between resonance frequencies due to increasing in temperature by 50
0
C is
almost 18 MHz.
The real part of input impedance is shown in Figure 25, the resonance value, resistance, of
input impedance at temperature 75
0
C is 0.959 GHz and 0.9608 GHz at temperature 27
0
C
which means, the difference is 18 MHz.
International Journal of Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
13
Figure. 21. 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.
Figure. 22. 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.
c) 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 as shown in Figure 23. 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.
Figure 24 shows the resonance frequency as a function of curvature for different temperatures.
The difference between resonance frequencies due to increasing in temperature by 50
0
C is
almost 18 MHz.
The real part of input impedance is shown in Figure 25, the resonance value, resistance, of
input impedance at temperature 75
0
C is 0.959 GHz and 0.9608 GHz at temperature 27
0
C
which means, the difference is 18 MHz.
International Journal of Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
14
Imaginary part of input impedance is illustrated in Figure 26 for radius of curvature 50 mm and
three values of temperatures -25, 27 and 75
0
C. Resonance values are the same as in real part,
peaks of real parts are at the same frequency of zeros for imaginary parts.
VSWR and return loss are shown in Figures 27 and 28 respectively, minimum values of VSWR
and return loss are in the same frequency for a peak values real part of input impedance and
same values of imaginary parts that give a zeros. Return loss value is almost -16 dB for all
values of temperatures.
Effect of temperature on normalized electric and magnetic fields are given in Figures 29 and 30
respectively. The effect of temperature on electric and magnetic fields is very small and we
could not determine the difference between curves. So, we can conclude that, the temperature
has no major effect on the radiation pattern on Epsilam-10 ceramic-filled Teflon substrate for
dielectric constant 10 and tangent loss 0.0015.
Figure. 23. Effective dielectric constant versus radius of curvature for cylindrical-rectangular and flat
microstrip printed antenna at different temperatures 75, 25 and -25
0
C.
Figure. 24. Resonance frequency versus radius of curvature for cylindrical-rectangular and flat microstrip
antenna for TM
01
at different temperatures 75, 25 and -25
0
C.
International Journal of Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
14
Imaginary part of input impedance is illustrated in Figure 26 for radius of curvature 50 mm and
three values of temperatures -25, 27 and 75
0
C. Resonance values are the same as in real part,
peaks of real parts are at the same frequency of zeros for imaginary parts.
VSWR and return loss are shown in Figures 27 and 28 respectively, minimum values of VSWR
and return loss are in the same frequency for a peak values real part of input impedance and
same values of imaginary parts that give a zeros. Return loss value is almost -16 dB for all
values of temperatures.
Effect of temperature on normalized electric and magnetic fields are given in Figures 29 and 30
respectively. The effect of temperature on electric and magnetic fields is very small and we
could not determine the difference between curves. So, we can conclude that, the temperature
has no major effect on the radiation pattern on Epsilam-10 ceramic-filled Teflon substrate for
dielectric constant 10 and tangent loss 0.0015.
Figure. 23. Effective dielectric constant versus radius of curvature for cylindrical-rectangular and flat
microstrip printed antenna at different temperatures 75, 25 and -25
0
C.
Figure. 24. Resonance frequency versus radius of curvature for cylindrical-rectangular and flat microstrip
antenna for TM
01
at different temperatures 75, 25 and -25
0
C.
International Journal of Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
14
Imaginary part of input impedance is illustrated in Figure 26 for radius of curvature 50 mm and
three values of temperatures -25, 27 and 75
0
C. Resonance values are the same as in real part,
peaks of real parts are at the same frequency of zeros for imaginary parts.
VSWR and return loss are shown in Figures 27 and 28 respectively, minimum values of VSWR
and return loss are in the same frequency for a peak values real part of input impedance and
same values of imaginary parts that give a zeros. Return loss value is almost -16 dB for all
values of temperatures.
Effect of temperature on normalized electric and magnetic fields are given in Figures 29 and 30
respectively. The effect of temperature on electric and magnetic fields is very small and we
could not determine the difference between curves. So, we can conclude that, the temperature
has no major effect on the radiation pattern on Epsilam-10 ceramic-filled Teflon substrate for
dielectric constant 10 and tangent loss 0.0015.
Figure. 23. Effective dielectric constant versus radius of curvature for cylindrical-rectangular and flat
microstrip printed antenna at different temperatures 75, 25 and -25
0
C.
Figure. 24. Resonance frequency versus radius of curvature for cylindrical-rectangular and flat microstrip
antenna for TM
01
at different temperatures 75, 25 and -25
0
C.
International Journal of Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
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Figure. 25. Real part of the input impedance as a function of frequency at different temperatures 75, 25
and -25
0
C and radius of curvature 50 mm.
Figure. 26. Imaginary part of the input impedance as a function of frequency at different temperatures 75,
25 and -25
0
C and radius of curvature 50 mm.
Figure. 27. VSWR versus frequency at different temperatures 75, 25 and -25
0
C and radius of curvature
50 mm.
International Journal of Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
15
Figure. 25. Real part of the input impedance as a function of frequency at different temperatures 75, 25
and -25
0
C and radius of curvature 50 mm.
Figure. 26. Imaginary part of the input impedance as a function of frequency at different temperatures 75,
25 and -25
0
C and radius of curvature 50 mm.
Figure. 27. VSWR versus frequency at different temperatures 75, 25 and -25
0
C and radius of curvature
50 mm.
International Journal of Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
15
Figure. 25. Real part of the input impedance as a function of frequency at different temperatures 75, 25
and -25
0
C and radius of curvature 50 mm.
Figure. 26. Imaginary part of the input impedance as a function of frequency at different temperatures 75,
25 and -25
0
C and radius of curvature 50 mm.
Figure. 27. VSWR versus frequency at different temperatures 75, 25 and -25
0
C and radius of curvature
50 mm.
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Figure. 28. Return loss (S11) as a function of frequency at different temperatures 75, 25 and -25
0
C and
radius of curvature 50 mm.
Figure. 29. 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.
Figure. 30. 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.
International Journal of Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
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Figure. 28. Return loss (S11) as a function of frequency at different temperatures 75, 25 and -25
0
C and
radius of curvature 50 mm.
Figure. 29. 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.
Figure. 30. 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.
International Journal of Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
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Figure. 28. Return loss (S11) as a function of frequency at different temperatures 75, 25 and -25
0
C and
radius of curvature 50 mm.
Figure. 29. 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.
Figure. 30. 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.
International Journal of Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
17
Conclusion
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
01
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
01
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.
References
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[10] S. Jacobsen, and P. Stauffer, “Multifrequency radiometric determination of temperature profiles in a
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Wireless Communications and Networking, July-Dec 2011, Accepted
International Journal of Computer Networks & Communications (IJCNC) Vol.3, No.5, Sep 2011
19
BIBLIOGRAPHIES
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.
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
implantable devices. He is also working on developing biomedical instruments and computation tools for
bioinformatics.
... Nevertheless, current automotive computing design is mostly based on semiconductor vendors' methods and models, typically neglecting temperature effects on interconnects. The effects of temperature performance have been studied mainly for antenna applications with Teflon based materials such as Polytetra Fluroethylene (PTFE) and Tetra Fluroethylene (TFE) as in [3], and also with Poly Vinylidene Fluoride (PVDF) materials which performance is studied in [4]. It's important to remark that Teflon based materials are not cost-effective for automotive electronics' applications. ...
... Its end launch SMA connectors are Johnson Components part number 142-0701-851 and are rated at an operating temperature of −65 to 165 °C, which makes the Samtec Golden Standard an ideal candidate for this work. 3 Device under test (DUT) was placed inside a Thermotron Industries model S-1.5-3800 environmental test chamber and connected to the VNA through Semflex 2121-DKF-0036 3.5 mm coaxial assembly cables. These cables were chosen since they are rated up to 26 GHz and have a temperature range from −65 to 200 °C. ...
Conference Paper
This work discerns the frequency response (up to 15 GHz) of several automotive-grade microstrip transmission line structures over a temperature span from-40 to 105 Celsius degrees. To ensure precise measurements, S-parameter responses from several test PCBs based on Cu over FR4 substrate are attained through a vector network analyzer in a controlled environment. Results show that temperature has a major impact on these high speed interconnects in frequencies above a few GHz, setting the need of employing accurate multi-physical models.
... Elrashidi et. al. 5 have done a detailed study on the effect of temperature on the resonance frequency of RT/Duroid 5880 PTFE substrate (manufactured by Rogers Corporation) which is one of the common substrate materials chosen for RF or microwave circuit fabrication. These authors have observed that a decrease in resonance frequency of almost 20 MHz occurs for a 50 C rise in temperature. ...
Conference Paper
Full-text available
For effective thermal management of high power and dense electronics, the heat sink forms the bulkiest component, and aluminum, owing to its light weight and easy machinability, is the preferred choice for airborne PCB devices used in aerospace and defense telecommunications. In this paper, we present a versatile and robust fabrication method to build circuit boards used for RF and microwave telecommunication devices over a large frequency of interest from MHz up to several tens of GHz range. Typically, 1 mil of copper is plated in the blind holes, followed by the desired final finish applied to it (nickel/gold, tin/lead, chromate). There can be several inner copper layers anchored to the blind holes. Cross sectional examination showed that the connectivity of the inner layer(s) with the barrel wall was very good and no delamination of the hole wall occurred even after 1,000 thermal cycles of (-40°C to +100°C) excursions were carried out in an automated thermal cycling chamber. Resistivity of the blind hole coupons with the 1 mil copper layer (protected by a 0.1 mil tin coating), with 300 mA of current applied, was always less than 0.0006 milli ohm even after 1000 thermal cycles.
... Elrashidi et. al. 5 have done a detailed study on the effect of temperature on the resonance frequency of RT/Duroid 5880 PTFE substrate (manufactured by Rogers Corporation) which is one of the common substrate materials chosen for RF or microwave circuit fabrication. These authors have observed that a decrease in resonance frequency of almost 20 MHz occurs for a 50 C rise in temperature. ...
... Hence, the value of Z 12 and Z 21 are given by Equation (19). (19) and the value of Z 11 and Z 22 are given by Equation (20). ...
Chapter
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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
... 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 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 cu rvature on the performance of a microstrip antenna as a function of temperature for TM 01 and TM 10 is introduced in [16], [17]. ...
Conference Paper
Full-text available
Curvature has a great effect on fringing field of a microstrip antenna and consequently fringing field affects effective d ielectric constant and then all antenna parameters. A new mathematical model for inpu t 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 RT/duroid-5880 PTFE substrate material. The range of operation is around 4.7 GHz.
Article
Multifunctional composites endowed with signal transmission and excellent mechanical properties show promising applications in aviation and aerospace. In this study, in combination with copper yarn, Kevlar yarn and polyimide resin, a light-weight 3D woven spacer composite antenna (3DWSCA) was developed for effective wireless signal transmitting. Based on the advanced 3D structural design, the Kevlar/Polyimide composite substrate with high specific strength (11.2 MPa/g·cm⁻³), ultra-low density (0.34 g/cm³), superb dielectric properties and small temperature coefficient of resonant frequency (TCF: -12.6 ppm/°C) was constructed. Accordingly, the 3DWSCA realized a gain value of 4.95 dB near designed frequency (2.34 GHz) with a good impedance matching (S11 value < −25 dB). Moreover, the 3DWSCA demonstrated broad temperature adaptability, maintaining stable resonance frequency and radiation properties in the temperature range of −160–200 °C. With these excellent performances, 3DWSCAs can be integrated into the component structure of high-velocity aircrafts to operate in a wide range of temperature, without sacrificing their mechanical and signal transmission functions.
Conference Paper
The cloud computing is considered as the next-generation of IT technology that can provide various elastic and scalable IT services in pay-as-you-go. This technology has been used by worldwide companies to improve their business performance. Therefore, authentication of both clients and services is a significant issue for the trust and security of the cloud computing. At present, to protect the security of the cloud, many ideas have been proposed. In this paper, we present DSA protocol concentrated on authentication of clients. It is an improved protocol based on Kerberos, which prevents password guessing attack by using dynamic session key. We also solved the problem of service availability by introducing two additional messages in the scheme.
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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.
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
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A half-wavelength long Teflon cable is part of a tuned circuit for the measurement of polarization in nuclear polarized targets. In trying to improve this measurement, the author noticed a large change in electrical cable length as the Teflon went through a room temperature chemical-molecular phase transition. Some test results on commercially available cables are reported. Teflon has room temperature phase transitions. The measurements indicated that the electrical length of the cable changed by 1000 ppm over a 13-19°C change. The thermal equilibrium signal peak is equivalent to a change of 1 ppm in the cable length. In the experiment the cables were heated to 26°C and hence improved this measurement by more than two orders of magnitude
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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.
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Space power systems and components are often required to operate efficiently and reliably in harsh environments where stresses, such as high temperature, are encountered. These systems must, therefore, withstand exposure to high temperature while still providing good electrical and other functional properties. Experiments were carried out to evaluate Teflon and ceramic capacitors for potential use in high temperature applications. The capacitors were characterized in terms of their capacitance and dielectric loss as a function of temperature, up to 200 C. At a given temperature, these properties were obtained in a frequency range of 50 Hz to 100 kHz. DC leakage current measurements were also performed in a temperature range from 25 to 200 C. The results obtained are discussed and conclusions are made concerning the suitability of the capacitors studied for high temperature applications.
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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.