WIRELESS SYSTEMS LABORATORY
LAB-REPORT- 1
EXPERIMENT 1:- DESIGN AND SIMULATION OF HALF-WAVE DIPOLE
ANTENNA
EXPERIMENT 2:- DESIGN AND SIMULATION OF QUARTER-WAVE
MONOPOLE ANTENNA
NAME: MEKONEN AMARE FENTAW
MAT NO: 739523
APRIL 02, 2022
HALF-WAVE DIPOLE AND QUARTER-WAVE MONOPOLE ANTENNA SIMULATION
Design and Simulation of Half-wave dipole antenna
1. Design
The discrete port is used as a generator its input impedance is 73Ω. I selected this value because
from theory I know that at resonance the real part of the impedance of the antenna is 73Ω, which is a
characteristic unique to the antenna. So, I base my choice depending on the previous knowledge of
my antenna. Calculation of parameters:- The frequency chosen is f = 1.5GHz, Wavelength, λ = c/f
Parameters of half-wave dipole antenna:- Input impedance (Zo) = 73Ω, the radius of dipole = .6mm
length of dipole(L) = 93.1mm, feeding gap of antenna = 0.3mm.
2. Result and Discussion
I. Scattering Parameter (reflection coefficient) S11: The reflection coefficient around a frequency
of 1.5 is almost -30 dB which is very small which means almost all the available power is entering
the antenna and will be radiated by the antenna.Originally, the half-wave dipole antenna simulation
isn’t working at 1.5GHz but after organizing and changing the length and radius value of the antenna,
works properly.
Figure 1 S-parameter result for L = 15 cm.
II. Z parameter: The dashed line refers to the imaginary part and the solid line the real part. By
zooming out the curve, I observed that at the resonant frequency which is 1.5GHz, the imaginary
part is become negative(-1.7107) and the real part is 73Ω.
Figure 2 Input impedance of the antenna
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HALF-WAVE DIPOLE AND QUARTER-WAVE MONOPOLE ANTENNA SIMULATION
III. Electric and Magnetic field Measurement:
Electric Field: There is quite a strong electric field in the feeding gap in the center of the antenna
which comes as no surprise because I am exciting the field of that gap. I also have a quite strong
field at the extremities of the cylinders which is also an expected one.
Figure 3 The Electric field distribution in a plane
Magnetic Field: The magnetic field is distributed along the length of the wire revolving around it. Its
distribution is very strong very near to the antenna and diminishes as we go further away and is all
as expected.
Figure 4 The magnetic field distribution view
IV. Radiation Pattern: I generally consider spherical coordinates in a spherically symmetrical
pattern. However, the antenna in practice is not Omnidirectional but has a radiation maximum along
one direction.
Figure 5 Far-Field Radiation Pattern for E-field for 1.5GHz
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HALF-WAVE DIPOLE AND QUARTER-WAVE MONOPOLE ANTENNA SIMULATION
Figure 6 Far-Field Radiation Pattern for Directivity for 1.5GHz
5. Conclusion:
Obtained results were acceptable for the practical implementation of these types of antennas.
Scattering loss obtained -30dB shows the characteristic of the reflection coefficient. Bandwidth was
observed as almost 200 MHz which is good enough to cover various wireless applications.
DESIGN AND SIMULATION OF QUARTER-WAVE MONOPOLE ANTENNA
1. Design:
To excite the antenna, I place a discrete port between the wire and the ground plane. The discrete
port is used as a generator its input impedance is 36 ohm which is half of the impedance used in the
dipole antenna. The calculation for parameters that control the value of the resonant frequency of the
antenna, the frequency chosen is f = 1GHz. Then Wavelength, λ = c/f = 0.3/1.5 [m] = 200mm, the
length of the wire must be, L = λ /4 = 50mm but I used L=92.3mm, Metallic cylinder wire with
radius R = 0.2mm is selected.
Figure 1 Monopole antenna design
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HALF-WAVE DIPOLE AND QUARTER-WAVE MONOPOLE ANTENNA SIMULATION
2. Simulation and Result
I. Scattering Parameter (reflection coefficient) S11: S-parameter of monopole antenna is
measured, the s11 value is measured designed antenna is -14.203 dB ranging at a frequency of
1.4954GHz. The exact position of the resonant frequency is influenced by the radius of the wire
and the thickness of the gap between the wire and the ground plane. scattering coefficient
depends on the reference impedance.
Figure 2 Scattering
Parameter
II. Z parameter: I see that the resonant frequency where the imaginary part is very small at a
frequency of 1.4775Hz. At this point, the real part of the impedance is around 23.48 Ohm. This
value is quite different from what I were expecting, and it is obvious as I am working with a real
device. By tuning the height of the monopole (length of the cylinder) and setting it to 92.3mm,
Figure 3 Input impedance of the antenna
III. Electric and Magnetic field Measurement:
Electric field: There is quite a strong electric field in the feeding gap at the lower end of the antenna and
upper extreme of the cylinder.
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HALF-WAVE DIPOLE AND QUARTER-WAVE MONOPOLE ANTENNA SIMULATION
Figure 4 The Electric field distribution in a plane (2D) at 1.5GHz
Magnetic Field: The magnetic field is distributed along the length of the wire revolving or curling
around it. Its distribution is very strong near to the antenna (the cylinder) and diminishes as we go
further away from the cylinder and is all as expected.
Figure 5 The magnetic field distribution 2D view at 1.5GHz
IV. Radiation Pattern: The radiation pattern looks like a “doughnut” shape, and I get that shape only at
the resonant frequency. By cutting that “doughnut” shape, I should have observed only the upper part
of the radiation pattern which is not the case. That is because there is some current flowing in the
ground plane which is contributing to the radiation pattern.
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HALF-WAVE DIPOLE AND QUARTER-WAVE MONOPOLE ANTENNA SIMULATION
Figure 6 3D plot of radiation pattern obtained at (theta = 90, f = 1.5GHz)
When I changed the side length of the ground plane to 150mm the radiation pattern shapes change a
little difference, the resonance frequency get shifted by 2.825GHz. Changing the resonant frequency
means changing the frequency where the imaginary part of the antenna impedance is zero. And
when that value is changed the scattering coefficient also get changed.
Figure 7 3D plot of radiation pattern obtained at (theta = 90, f = 1.5GHz)
CONCLUSION:
Both monopole and dipole antennas exhibit similar radiation patterns and performance, except that
monopole antennas are not symmetric vertically.
The size and design constraints of requiring a ground plane for monopole antennas is often
restrictive and the radiation pattern of the monopole depends on the orientation of the ground plane.
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