WiFi Antenna Laborotory Report

Sanzhar Askaruly

Nazarbayev University, School of Engineering

Lab #3 Introduction In this lab work, we are to discover WiFi Antenna of Mobile Phone. Specifically, with the help of Wifi Analyzer app, downloaded from Play Store, we record measurements of WiFi antenna at various conditions. For the equipment part, Lenovo P780 was used. The lab work covers two parts: Part 1: WiFi Antenna Location Part 2a: WiFi Antenna Radiation Pattern Background According to GsmArena (Lenovo P780: Full Phone Specifications), Lenovo P780 uses popular 802.11 a/b/g/n wireless protocol, supports dual-band and Wi-Fi tethering. IEEE 802.11 is a set of specifications for wireless communication, usually working on 2.4, 3.6, 5 and 60 GHz frequency bands. Dual-band phone means that it receives signals on two specific frequencies, always defined. WiFi tethering means that mobile phone can serve as hubspot: it can route other devices to Internet using local WiFi antenna. Methods and Methodology Part 1: WiFi Antenna Location In this part of the Lab Work, we are asked to determine the location of WiFi antenna in the cellphone. Initially, we tried to use foil aluminum foil by covering some parts of the cellphone. However, due to the random results that we got, we tried to look for the information in the Internet. From there, we observed that WiFi antenna is located in the top half of the phone. Indeed, experimentally this hypothesis was proven.

Antenna Location at Lenovo P780

Sanzhar Askaruly

Nazarbayev University, School of Engineering

After covering the top half with aluminum foil, the amplitude of WiFi signal significantly decreases. Channel graph and Signal meter tools of WiFi Analyzer were used to prove the abovesaid.

Part 2a: WiFi Antenna Radiation Pattern In this part of the lab, we are asked to measure the RSSI parameter of the received signal during the horizontal rotation and vertical rotation of mobile phone. During this procedure, the phone was located at the distance of 23 meters from the router, put on a chair. In fact, we used 4 positions during the rotation, from 0 to 270 with the step of 90 degrees for both horizontal and vertical rotation.

Results The wireless network parameters: Name of Network: NUdormitory MAC address: 58:97:1e:ed:2c:c1 Frequency: 2412 MHz Channel: Channel 1 We started from recording the RSSI values for horizontal rotation. Only average values were put into the table: horizontal rotation

without hand

with hand

Angle

Intensity, dBm

Intensity, dBm

0

-52.8

-53.8

90

-50.0

-46.0

180

-44.8

-46.6

270

-49.0

-44.0

Sanzhar Askaruly

Nazarbayev University, School of Engineering

After the data is collected, the plots are generated in MATLAB. The code snippet & appropriate output polar form graph are illustrated below: function WithoutHandsHorizontal theta = 0 : pi/2 : 2*pi; RSSI1 = [-52.8 -50 -44.8 -49.0 polar(theta, RSSI1); hold on function WithHandsHorizontal theta = 0 : pi/2 : 2*pi; RSSI2 = [-53.8 -46 -46.6 -44.0 polar(theta, RSSI2); end

-52.8]

-53.8]

Horizontal Rotation Polar Plot (Red line – handless rotation, black line – with hand) Next, we continue the procedure of WiFi analyzer with vertical rotation. Since we use the same router, no of network parameters is changed. Name of Network: NUdormitory MAC address: 58:97:1e:ed:2c:c1 Frequency: 2412 MHz Channel: Channel 1 The RSSI values for vertical rotation are then recorded. Only average values were put into the table: vertical rotation

without hand

with hand

Angle

Intensity, dBm

Intensity, dBm

0

-51.6

-60.0

90

-50.4

-53.4

180

-51.0

-49.4

270

-52.0

-53.6

After the data is collected, the plots are generated in MATLAB. The code snippet & appropriate output polar form graph are illustrated below: function WithoutHandsVertical theta = 0 : pi/2 : 2*pi; RSSI1 = [-51.6 -50.4 -51.0 -52.0 -51.6] polar(theta, RSSI1); hold on function WithHandsVertical theta = 0 : pi/2 : 2*pi; RSSI2 = [-60 -53.4 -49.4 -53.6 -60] polar(theta, RSSI2); end

Sanzhar Askaruly

Nazarbayev University, School of Engineering

Vertical Rotation Polar Plot (Red line – handless rotation, black line – with hand) Discussion To explain, the power plots The Friis Transmission equation is needed. The given formula (Friis Transmission Equation) shows the ratio of received power to the transmitted power. In idealized conditions, this ratio converges to 1.

or

- Power available at the receiving antenna - Power available at the transmitting antenna - transmitting antenna gain - receiving antenna gain - wavelength - distance between antennas From the formula, it can be noted that power at the input of receiving antenna is inversely proportional to the distance between antennas, with other parameters constant. The further the cellphone antenna, the less power at its input. From the first table for horizontal rotation, it can be seen that at zero degrees (the receiving antenna is at closest position to transmitting antenna) intensity is the largest for both cases (with & without hand). And for 180 degrees (the receiving antenna is at the farthest position), power intensity is the least. For vertical rotation, it is trickier. Here, even if the rotation happens, the distance may not become less, but as opposed, it can even increase, since we should consider three-dimensional space. But generally, with naked eye, we can observe that power intensity also decreases.

Sanzhar Askaruly

Nazarbayev University, School of Engineering

Conclusion In this lab, we learnt how Friis Transmission Formula can be applied to explain power intensity changes of WiFi signals at the mobile phone antenna. We empirically observed intensity dependence on the distance between antennas. Moreover, we discovered one more useful tool in analysis of WiFi signals, called WiFi Analyzer, which was great in assisting in understanding real time WiFi signals.

Reference: Friis Transmission Equation. Retrieved 12/11/2014 from http://en.wikipedia.org/wiki/Friis_transmission_equation Lenovo P780: Full Phone Specifications. Retrieved 12/11/2014 from http://www.gsmarena.com/lenovo_p780-5544.php Yerlan Rizukov. Data obtained from WifiAnalyzer on Lenovo P780 Phone. The data was collaboratively traced due to the absence of personal smartphone