Design of a UHF Pyramidal Horn Antenna Using...
Transcript of Design of a UHF Pyramidal Horn Antenna Using...
Design of a UHF Pyramidal Horn Antenna Using CST
Biswa Ranjan Barik and A.Kalirasu
Department of EEEM, AMET University , Chennai, India
[email protected] and [email protected]
Abstract
This technical paper highlights about design of pyramidal horn
antenna and simulation of its parameters using computer simulation
technology. Horn antennas are extensively used in the fields of T.V.
broadcasting, microwave devices and satellite communication. Since
horn antennas do not have any resonant elements they operate at
wide range of frequencies and have a wide bandwidth. They are also
used as high gain devices in phased arrays and as a feeder for
reflector and lens antennas in satellite communication. The material
used in the design of antenna is Perfect Electric Conductor (PEC).
The designed Pyramidal horn antenna is functional for each UHF-
band applications and here it is having gain of 5dB operating at
2.8GHz frequency. The performance parameters like Directivity,
impedance, Efficiency, s-parameters are evaluated using CST
Key Words:- Horn Antenna, resonant element, Phased arrays,
Feeder, PEC,CST
1. Introduction
The horn antenna is most widely used simplest form of microwave
antenna, which comes from the aperture antenna family. The first horn
antenna was constructed by an Indian radio researcher and one of the father
of radio science Jagadish Chandra Bose (1858-1937), in the year 1897. The
horn makes a transition of EM waves propagating in a waveguide, and
launches it into free space. The flaring of the metal helps in the gradual
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matching of the impedance of the waveguide, usually 50 Ω, to that of the
free space i.e., 377 Ω. The advantages of a horn are its wide bandwidth, low
VSWR and simplicity of construction and adjustment. They are designed in
variety of shapes and sizes to fulfill many practical applications, such as
communication systems, electromagnetic sensing, directive antenna
applications, microwave applications, biomedical applications and as a
reference source for testing of other antennas. These horns can be used as
feeds for other antennas such as reflectors, compound and lens antennas.
Due to such a vast area of application and advantages, the horn antenna can
be preferred over other aperture antennas. Basically the horn antennas are
classified as rectangular horn antennas and circular horn antennas. The
rectangular horns are further divided into sectoral horn and pyramidal horn.
The sectoral horn is divided into two types based on the direction of flaring
in accordance of the field vectors. The E – plane sectoral horn is obtained
when the flaring is done in the direction of the electric field vector . The H
– plane sectoral horn is obtained when the flaring is done in the direction of
the magnetic field vector. When the flaring of the walls of the waveguide is
done along the direction of both E and H field vectors, it gives rise to a horn
called Pyramidal Horn The pyramidal horn antennas are the most
extensively used antennas since they have the combined characteristics of
both E – plane and H – plane sectoral horns.
2. Antenna Parameters
The characteristics of an antenna can be understood by the antenna
parameters. The various parameters such as radiation pattern, beam width,
directivity, radiation intensity help us for the analysis of an antenna.
2.1 Antenna Radiation Pattern
It is the graphical representation of electric and magnetic fields at all points
equi-distance from the antenna. It gives radiation properties of an antenna
as a function of space coordinates. If it is measured in terms of volts/m then
it is called “Field Radiation Pattern”. If it is measured in terms of power per
unit solid angle, then it is called “Power Radiation Pattern”. The relative
measure of magnitude of the antenna’s ability to direct or concentrate the
electromagnetic energy in a particular direction or pattern is called “Gain”.
It is measured in decibels. The expression to calculate the Gain is
max( , )
...........(1)( , )average
PD
P
The Directivity of an antenna is its capability to direct or concentrate the
radiated power in a particular direction and attenuate in undesirable
directions.
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4
4 4...................(2)
( , ) An
DP d
Radiation intensity is the measure of the power radiated from an antenna per unit
solid angle in a given direction. It is a far-field parameter. Total power radiated is
given by
2
0 0
sin .............(3)radP Ud U d d
3. Design Equations of Horn Antenna
The electromagnetic horn produces uniform phase front with larger aperture
as compared to wavelength. Because the horn aperture, at higher
frequencies, is electrically larger when compared to wavelength. Due to
this the directivity increases. Assuming that there is a line source which
radiates cylindrical waves, and the dimensions of the imaginary apex of
the horn as shown in the figure. Where, δ is the difference in the path of
travel, θ is the flare angle, h is the height of aperture, ρ is length of aperture.
Fig:1 Section view of Horn Antenna
Then from geometry[4]
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.....................................(4)COS
Also
2tan ..................................(5)
2
hh
Hence we get
1 1tan .................(6)
2
hCOS
The angle θ represented in equation is called the optimum aperture angle.
The directivity of maximum value can be obtained at the largest flare angle
for which the path difference does not exceed typical values of 0.32 λ for
conical horn, 0.25 λ for plane horn and 0.40 λ for H – plane sectoral horn
antenna. Because of more than one flare angle the pyramidal and conical
horn antenna has the highest directivity compared to any other horns.
For optimum flare horn, the half power beam width can be approximated as
67
......................(7)H
Ha
And
56........................(8)E
Ea
Directivity in terms of effective aperture of the horn as
2 2
44...................(9)
ap peAA
D
Where Ae is effective aperture, in m2,
Ap is physical aperture, in m2 ,εap = Ae /Ap is Aperture efficiency
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4. Pyramidal Horn Antenna using CST
The pyramidal antenna is generally excited using a waveguide which is fed
with a coaxial cable. The antenna here is constructed using a simulation
software called Computer Simulation Technology (CST) and it is assumed
that antenna is made up of PEC; the plates of finite thickness are modeled
as infinitesimally thin plates resulting in surface currents that represent the
sum of interior and exterior antenna currents. This software has the
maximum of 30,000 cells.The geometry of a horn antenna with spatial
coordinates is as xmin = -25; xmax = 25 and ymin = -14; ymax = 14 and zmin = 0
and zmax = 70 modeled as shown in Figure. Pyramidal flare of horn antenna
is the most significant part in the antenna design, which varies the
impedance of waveguide from 50Ω at the feeding point to 377Ω at the
aperture of the antenna. The symmetry feature in both electric and magnetic
planes can be used, so as only half or quarter of given antenna can be
modeled. The gain obtained is 5.50 dB approximately, near field is
observed and analysis characteristics for different models of antenna at
various frequencies are observed.
Fig. 2 Pyramidal Horn Antenna using CST
5. Simulation and Experimental Results
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Fig. 3. S- Parameter
Fig. 4 VSWR
Fig. 5. Power Excitation Signals
Fig. 6. Input Excitation Signal
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Fig. 7. 3D Plot of gain for 3GHz
Fig. 8. Polar Plot of gain for 3GHz
Fig. 9. Polar Plot of gain for 6GHz
Fig. 10. 3D Plot of gain for 6GHz
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Figure-1 Shows the analysis of the design with S(1,1) parameters. S-
parameters are called complex scattering parameters because both the
magnitude and phase of the input signal are altered by the network. Due to
impedance mismatch some energy is reflected back in the system which is
called as return loss (dB). It is a numerical measure of dissimilarity between
impedances of loads and metallic transmission lines. It is important in
applications that use simultaneous bidirectional transmission. Larger values
of it indicate less reflection. The value of -15 to-20 dB and higher are
considered acceptable.
Figure-2 shows VSWR graph. Voltage standing wave ratio gives the
value that how our antenna is matched with transmission line impedance or
with load resistance. The simulated value for voltage standing wave ratio is
less than 2 and hence can be fair for signal transmission when low
attenuation is present. It also concludes that the designed antenna is
matched to the operating frequency. Both VSWR and Return loss play an
important role in the study of transmission from antenna and reception of
signal.
Figure-3 shows the power excitation of the designed antenna. The
amount of power accepted, radiated, Power outgoing of all port and power
stimulated
Figure-4 shows the default excitation signal which is used to activate the
antenna.
Figure-5 shows the 3D and polar plot of gain which shows the magnitude
of main lobe for the designed Pyramidal horn antenna. The value is found
to be 5.49 dBi.
6. Conclusion
The successful implementation and simulation of pyramidal horn antenna is
done by using CST. As a result of experimental studies, it is evident that
signal integrity be intercepted or transmitted depend on the design
considerations of the pyramidal horn antenna. These antennas can be
enhanced using dielectric lens, good conductive materials and ridges. They
are used significantly where directivity of signal is of main concern. CST is
a useful tool for better 2D and 3D analysis and design of antenna structure
within small time. By using CST simulation results, we have designed our
antenna of gain 5dB with a resonant frequency of 2.8GHz, VSWR is 2 and
normalized impedance of 50Ώ.
References
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[1] Ayodele S.Oluwole,viranjan M.Srivastava, “Design of smart antenna using waveguide-fed pyramidal horn antenna for wireless communication systems”, IEEE(INDCON),2015. [2]. N.Smitha,Vipula Singh,S.N.Sridhara, “Pyramidal horn antenna for ground penetrating radar application”, IEEE(INDICON), 2016. [3] Katsushige Harima, Makato Sakasai, Katsumi Fujji, “Determination of gain for pyramidal horn antenna on basis of phase center location”, IEEE (ISEC), 2008. [4]. Deqinsyang, Sihaolio, Bao Sun, Jin Pan, “Research on Pyramidal Horn Antenna using integrating optical E – field probe”, IEEE (APMC), Vol.3, 2015. [5] Chintin A. Patel, Shobhit K. Patel, “Pyramidal Horn antenna design loaded by meta – material for performance enhancement”, IEEE (MEMO), 2015. [6]. Aniket Bhumkar, “Design and Implementation of Pyramidal Horn Antenna,” IJRASET, Vol. 3 Issue V, May 2015. [7] Arvind Roy, “Design and Analysis of X band Pyramidal Horn Antenna Using HFSS,” IJARECE, Vol. 4 Issue 3, March 2015. [8] Daniyan O.L., “Horn Antenna Design: The Concepts and Considerations,” IJETAE, Vol. 4 Issue 5, May 2014. [9]Priyanka Bhagwat, “High gain Conical Horn Antenna for short range communications”, IJERA, Vol 3 Issue 6, Nov-Dec 2013. [10]. Arvind Roy, Isha Puri, “Design and Analysis of X band Pyramidal Horn Antenna Using HFSS”, IJARECE, Volume 4, Issue 3, March 2015. [11]. G.Abhignya, B.Yogita, C.Abhinay, B.Balaji, MBR Murthy, “Design, fabrication and testing of pyramidal horn antenna”, IJEAS ISSN: 2394-3661, Volume-2, Issue-4, April 2015
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