Module 5.3
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Apr 3, 2024
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Friis Transmission Formula
Name
ENGR 101-Introduction to Engineering
April 23, 2023
Abstract
In this experiment, we tested a dipole and dish antenna to determine whether the basic elements of the antennas contributed to the amount of RSSI under a change of distance. This was done in the ERAU Hub Communications Lab by supplying a 0.75-watt power supply to each antenna at a different distance to measure the received signal strength (RSSI). The Friis Equation was used to determine the amount of power an antenna receives from sending the antenna at various distances. The findings of this experiment will show that the RSSI of the dish antenna slowly decreased with Friis equation when the distance was increased while the dipole antenna’s RSSI decreased at a faster rate. This experiment proves that the amount of RSSI is dependent on the distance between two antennas.
1. Purpose
This experiment aims to study the design and performance of two types of antennas in free space. The basic antenna theory was used to observe the performance of a dish and a dipole antenna at various distances with a power of 0.75 watts. By testing two types of antennas at different distances, we can determine whether the basic design elements of each antenna contributed to the amount of power of the RSSI. The findings of this experiment will be represented by the procedures, results, and conclusions.
2. Theory
Unmanned aircraft systems, commonly referred to as drones, operate at various levels of autonomy. When operating at the lowest scale, UAS navigation relies heavily on
radio frequency (RF) to transmit and receive signals from a power source. The received signal diminishes under idealized conditions, limiting the vehicle's operating range. In this lab, the Friis Equation was used to determine the relationship between the amount of power an antenna receives from sending the antenna at various distances. Fig 1
. Friis Equation Basics
P
t
: power at receiving antenna.
P
t
: output of transmitting antenna
G
r
, G
r
: gain of the transmitting and receiving antenna.
: Wavelength
R: distance between antennas
3. Equipment and Supplies
To test the two types of antennas, the ERAU Hub Communications Lab was utilized to stimulate a change in the distance between the sending and receiving antennas. Microsoft Excel was used to generate a graph from the data exported from this lab. The figures below demonstrate the findings of this experiment.
Fig. 1
– Experiment Setup
Figure 1 displays the dish antenna in the initial setup of the lab in the ERAU Hub Communications Lab. On the right-hand side, the figure displays the user control panel. This allows the user to navigate between dipole and dish. Additionally, this panel allows the user to adjust the obstacle, power, pitch, and heading data. Hence, the “pitch”, “heading”, and “change obstacles” controls remained constant in this experiment. Currently, the power supply is set at 0.5 watts 20 feet away from the UAS with an RSSI measuring -7.2176 dB.
.
Fig 2
- Dish antenna
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Figure 2 shows the dish antenna with a power supply of 0.75W 3000 feet away from the UAS. The RSSI is currently measuring at -49.1551 dB. The “pitch”, ‘distance” and “change obstacles” controls were not altered during this testing. .
Fig 3-
Dipole Antenna Figure 3 demonstrates the dipole antenna 3000 feet away from the UAS with a power supply of 0.75 watts. The “pitch”, ‘distance” and “change obstacles” controls were not altered during this testing. We can observe that the RSSI of the dish antenna significantly dropped from -7.21dB at the initial setup to -57.782 dB when the antenna was moved farther away. 4. Observations/Measurements Table 1 – Antenna Properties
P
t
0.75
W
-5.155
dB
Gt
6
dB
Gr
6
dB
Freq
2.4
GHz
Wavelength
0.1249
m
The following design parameters were set to perform this experiment.
a.
Set up the dipole and dish antenna at a fixed P
t
of 0.75W.
b.
For each antenna, use the “distance” control to gradually increase the distance from 20 feet to 3000 feet.
c.
Once done, export the data into Microsoft Excel.
d.
Utilizing the Friis Equation, calculate the RSSI for the various distances for each antenna.
e.
Compare and contrast the RSSI values from each antenna with the theoretical values of the Friis Equation.
f.
To calculate the RSSI, we used: 0
500
1000
1500
2000
2500
3000
3500
0
500
1000
1500
2000
2500
3000
3500
0
2
4
6
8
10
12
-70
-60
-50
-40
-30
-20
-10
0
RSSI vs Distance
Friis Equation
Dipole
Dish
R (ft)
RSSI (dBm)
Fig 4
-RSSI v. Distance Graph
Figure 4 shows the relationship between the Friis equation and the two types of antennas. The graph shows that both antennas decreased gradually with the Friis equation from 20 feet to 3000 feet. The RSSI of the dipole antenna decreased at an average of 1 dB while the dish antenna gradually decreased by 0.4 dB. The graph shows
the dish antenna as having a wider beam than the dish antenna when moving from 0 to 250 feet.
5. Discussion
We were able to apply a 0.75-watts power supply effectively to the dish and dipole antennas when testing these antennas at various distances. A factor that introduced
uncertainly in this experiment is when we manually toggled the distances of each antenna. As a result, the measurements of the received signal strengths only produced estimated measurements in comparison to the Friis equation. Based on the graph, we can observe that the RSSI is dependent upon the distance between two antennas. 6. Conclusion
a.
In the conclusion, restate the labs purpose. b.
Describe in detail what you learned and how the lab might be useful in the future. In this experiment, we aimed to study the design and performance of two types of antennas in free space. The basic antenna theory was used to characterize the difference in the performance of a dish and dipole antenna with a power of 0.75 watts by
measuring the RSSI as a function of distance. This was done by testing the dish and dipole antenna at various distances. Based on our data, we can observe that both antennas decreased in RSSI when the antenna moved farther away from the UAS. Additionally, the theoretical values of these antennas showed a clear relationship between the distance and the amount of received signal strength when compared to the Friis equation. The results proved that the amount of distance between two antennas limits the range of the RSSI. This experiment is important because antennas are a major component in our wireless communications. An antenna is designed to receive and transmit guided waves within a transmission line to radiated free-space waves (Balanis, 1992). The directional function of this device allows us to transmit information efficiently to a UAS. The results of this experiment prove that the receiving signal strength weakens when an antenna is moved farther away. The Friis basic equation used allows us to measure the amount of power from two antennas under idealized conditions which are critical for our UAS.
References
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C. A. Balanis, "Antenna theory: a review," in
Proceedings of the IEEE
, vol. 80, no. 1, pp. 7-
23, Jan. 1992, doi: 10.1109/5.119564