Antennas Term Project

[Belge alt konu başlığı]

17 ARALIK 2013

Microstrip Rectangular-Edge Fed Antenna for 2.4 GHz Wi-fi Applications

1) Wi-fi Technology

As of today, Wi-Fi (also known as WLAN) has become a standard in most computers. Almost every modern mobile phone and other gadgets are being implemented with Wi-Fi technology. Wi-Fi makes it possible for the user to connect to the internet or LAN (Local Area Network) through a wireless connection . WLAN uses the technical term “IEEE 802.11” and has standards in the names of 802.11 b/g/n. Wi-fi operates on both 2.4 GHz and 5 GHz and uses 11 carriers to carry data. Wi-fi is a good alternative to LAN’s since it can be used in places where it is hard to run cables such as outdoor and historical places.

2) Microstrip Patch Antenna

The microstrip antenna, because of its small size, lightweight, lowprofile, and low manufacturing cost has many application areas such as mobile satellite communications, directbroadcast satellite services, global positioning system, medical hyperthermia usage, etc.The Basic parameters and shape of the microstrip patch antenna is as follows:

L : Length of the microstrip patch

W : Width of the microstrip patch

t : Thickness of patch

h :Height of the dielectric substrate

3) Microstrip Patch Antenna Design and Simulation

A rectangular edge-fed microstrip patch antenna is designed for 2.4 GHz center frequency, substrate relative permitivity of 2.2 (ε) and substrate height (h) of 1.574 mm. HFSS 13.2 is used for the design of the antenna.Using our chosen design parameters , we should calculate dimensions of the microstrip antenna patch, substrate and feed line.

Using this formula we find the width of the patch W = 41.36 mmThen we calculate dielectric constant of the substrate εreff by the formula:

Εreff = 2.2We need to find length of the patch :

L = 49.41 mm

Necessary condition for finite and infinite ground plane can be satisfied if the dimensions of the ground is 6 times of the h greater than the patch dimensions.

Noting the substrate dimensions are as same as the ground plane,

Lsubstrate = 83.6 mm Wsubstrate = 172.57 mm Edge feed W = 1.885 mm Edge feed L = 23.418 mm Feed width = 4.852 mm Feed length = 38.075 mm

These parameters are used to create and simulate the rectangular edge-fed microstrip antenna in HFSS.

Simulation result of the antenna are as follows:

Return loss

Higher return loss values at the operating frequency are desired since more loss at return means that most of the wave is not reflected but transferred to antenna.

Input Impedance

Input impedance of the antenna must match the impedance of the feed line in order to eliminate loss power due to mismatch.

Radiation pattern (phi 0-180 degrees)

As we can see from the plot, we have maximum radiation intensity at theta = 0.

Intensity values stays almost the same along the horizontal axis.

2-D Gain

Gain has its highest value as we expected from the radiation pattern plot.

Gain (theta =0 ) = 6.94 dB

3-D Gain Pattern

3-D plot of the gain also gives us the radiation pattern of the antenna since radiation intensity and gain is strictly related to each other.

Voltage Standing Wave Ratio

It is expected to have a small value of VSWR around the operating frequency.

VSWR = (1+p)/(1-p)

Where

P : reflection coefficient

Simulation Results

In this work a rectangular edge-fed microstrip patch antenna was designed using Ansoft HFSS for 2.4 GHz wi-fi applications. Substrate with dielectric constant of 2.2 and height 1.574 mm was chosen.Various antenna parameters were studied to evaluate the performance of the antenna. Designed antenna has high return loss, matched input impedance, low VSWR within the desired frequency band. Antenna provides 6.94 dB gain at the chosen frequency.