International Journal of Engineering Trends and Technology (IJETT) – Volume 8 Number 5- Feb 2014
Comparative Analysis of Rectangular Waveguide
and Coaxial Cable Using H.F.S.S
SK Masud Hossain1, Syed Mahammad Ashif1, Subhajit Ghosh1, Diptyajit Das2, Samsur Rahaman3
1Department of Electronics and Communication Engineering, WBUT, Kolkata, India,
2Department of Bio Medical Engineering, WBUT, Kolkata, India ,
3Department of Electronics and Communication Engineering, Bengal Engineering & Science University, Shibpur,India
Abstract— This paper proposes new designs to eliminate
attenuations present in the transmission line by means of
perfect matching of the ports through two models coaxial cable and rectangular waveguide. This paper also
depicts the various conditions for propagation of waves
through the structures.
Keywords— Lumped Port, Wave Port, Standing wave
pattern, Perfect Matching, E & H field.
1. INTRODUCTION
Coaxial
cable is
a
type
of
cable
for
high bandwidth data transmission use that typically
consists of a single copper wire that is surrounded by
a layer of insulation and then by a grounded shield
of braided wire or an extruded metal tube. The whole
thing is usually wrapped in another layer of
insulation and, finally, in an outer protective layer.
The grounded metal tube or braided wire shield
minimizes electrical interference and radio frequency
interference (RFI) and results in a much greater
bandwidth (i.e., data transmission capacity) than does
conventional copper wire cable (but less than optical
fiber cable). The metal tube type has a greater data
transmission capacity but is rigid and thus is used
only for specials situations; the braided type is much
more flexible and easier to use. Connections to the
ends of coaxial cables are usually made with
specially designed RF (radio frequency) connectors.
Whereas waveguides are used principally at
frequencies in the microwave range; inconveniently
large guides would be required to transmit radiofrequency power at longer wavelengths. In the XBand frequency range of 8.2 to 12.4 GHz, for
example, the U.S. standard rectangular waveguide,
WR-90, has an inner width of 2.286 cm (0.9 in.) and
an inner height of 1.016 cm (0.4 in.). Rectangular
waveguides are commonly used for power
transmission at microwave frequencies. Their
physical dimensions are regulated by the
frequency of the signal being transmitted. In this
paper we discuss various criteria for propagation of
ISSN: 2231-5381
the waves through coaxial cable and rectangular
waveguide. The paper depicts the perfect modeling of
coaxial cable and rectangular waveguide for perfect
propagation of waves and without any distortion or
attenuation.
2. MODEL ANALYSIS
2. A. Coaxial Cable Model
2. A.1.Design. Coaxial cable is a self-shielded cable
used for transmission of communications signals,
such as those for television, telephone, or computer
networks. A coaxial cable consists of two conductors
laid
concentrically
along the
same
axis.
One conducting wire is surrounded by a dielectric
insulator, which is in turn surrounded by the other,
outer conductor, producing an electrically shielded
transmission circuit. The whole cable is wrapped in a
protective plastic sheathing. The signal propagates
within the dielectric insulator, while the associated
current flow is restricted to adjacent surfaces of the
inner and outer conductors. Our design is a coaxial
cable of length l=200 mm, inner radius r1=0.6375
mm, intermediate radius r2=2.0125 mm, outer
radius=2.5 mm. The substrate is kept between inner
and outer cylinders and it has a dielectric constant €r
of 1.9. The frequency of operation is fixed about 4
GHz.
Fig.1 Designed Diagram of Coaxial cable.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 8 Number 5- Feb 2014
2. A.2.Observations. We observed the E & H field
and the direction of propagation of wave along a line
created just above the inner cylinder when all the
afore mentioned aspects are gratified.
Fig. 2 Line of observation in between the inner and outer cylinder.
2. A.2.1. BOTH PORTS ARE MATCHED AND HAVE
RESISTANCE 50 OHMS
After both the ports are matched perfectly and are
assigned resistances of 50Ωs in each port ,we
observed E-field along Y-axis, H-field along X-axis
and full transmission happens with no attenuation or
very little attenuation in the Z direction. The wave
behavior is presented in sequential order.
Fig. 3 Schematic diagram represents wave propagation in different
axis in sequential order.
2. A.2.2 PORT 2 IS ASSIGNED WITH LUMPED
PORT AND ALLOTED A RESISTANCE OF 0.005
mΩ (VERY LOW RESISTANCE).
When port1 is assigned a resistance of 50Ωs and
port2 of 0.005mΩ we observed E-field along Y-axis,
H-field along X-axis but no propagation of wave in
the cable and a standing wave pattern is observed.
The wave manner is displayed in a sequential order.
ISSN: 2231-5381
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International Journal of Engineering Trends and Technology (IJETT) – Volume 8 Number 5- Feb 2014
Fig. 5 Schematic diagram represents wave propagation in different
axis in sequential order.
2. B. Rectangular Waveguide Model
Fig. 4 Schematic diagram represents wave propagation in different
axis in sequential order.
2. A.2.3 PORT 2 IS ASSIGNED WITH LUMPED
PORT AND ALLOTED A RESISTANCE OF 1400
MΩ (VERY HIGH RESISTANCE).
When port1 is assigned a resistance of 50Ωs and
port2 of 1400 MΩ again we observed E-field along
Y-axis, H-field along X-axis but no propagation of
wave and a standing wave pattern is observed. The
wave behavior is shown in sequential order
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2. B.1.Design. In general, a waveguide consists of a
hollow metallic tube of arbitrary cross section
uniform in extent in the direction of propagation.
Common waveguide shapes are rectangular, circular,
and ridged. The rectangular waveguide has a width a
and height b as shown in figure. In our design inside
a cuboid another cuboid is placed and the cavity is
kept hollow. In this model length l=100mm, width
a=0.9 inch, height b= 0.4 inch and thickness t= 2 mm.
Substrate is not used in this model and the frequency
of operation is set at 10GHz.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 8 Number 5- Feb 2014
Fig. 6 Designed diagram of rectangular waveguide.
2. B.2.Observations. We observed the E & H field
and the direction of propagation of wave along an
experimental vertical plane when all the afore
mentioned aspects are satisfied.
Fig.7 Observation along experimental vertical plane for the above
condition.
2. B.2.1 BOTH PORTS ARE MATCHED AND
ASSIGNED RESISTANCES OF 50 OHMS
When observed along any experimental vertical
plane, we get the following wave pattern. We can
observe-E-field along Y-direction, H-field along Xdirection and the wave propagates in z direction with
no attenuation or very tiny attenuation. The wave
behavior is presented in successive order.
ISSN: 2231-5381
Fig.8 Schematic diagram represents wave propagation in different
axis in sequential order.
2. B.2.2 PORT 2 IS ASSIGNED WITH LUMPED
PORT AND ALLOTED A RESISTANCE OF 0.001
mΩ (VERY LOW RESISTANCE).
Very similarly in this case when port1 is assigned a
resistance of 50Ωs and port2 of 0.001mΩ we can
observe E-field along Y-axis, H-field along X-axis
but no propagation of wave and a standing wave
pattern is observed. The wave actions are shown in
sequential order.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 8 Number 5- Feb 2014
3. CONCLUSION
All the above results have been done in Ansoft
H.F.S.S 11.0 wbb version. By regulating the
frequency of the transmitted signal and by means of
perfect matching of wave ports a signal can be
transmitted all through the transmission lines and
wave guides without any distortion. In waveguides
the electric and magnetic fields are confined to the
space within the guides. Thus no power is lost to
radiation. Since the guides are normally filled with
air, dielectric losses are negligible. However, there is
some I2R power lost to heat in the walls of the
guides, but this loss is usually very small.
4. REFERENCES
Fig.9 Schematic diagram represents wave propagation in different
axis in sequential order.
2. B.2.3 PORT 2 IS ASSIGNED WITH LUMPED
PORT AND ALLOTED A RESISTANCE OF 2000
MΩ (VERY HIGH RESISTANCE).
Very similarly in this case when port1 is assigned a
resistance of 50Ωs and port2 of 2000 MΩ we can
observe E-field along Y-axis, H-field along X-axis
but no propagation of wave and a standing wave
pattern is observed. The wave behavior is shown in
sequential order.
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Fig.10 Schematic diagram represents wave propagation in different
axis in sequential order.
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