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EXPERIMENT NO.4

Analysis of Microstrip Patch Antenna

Time

( min)

Content

Learning Aid / Methodology

Faculty Approach

Typical Student Activity

Skill / Competency Developed

10

Relevance and significance of experiment

Chalk & Talk , Presentation

Introduces, Facilitates, Monitors

Listens, Participates, Discusses

Knowledge, Communication, intrapersonal

20

Explanation of experiment

Chalk & Talk , Presentation

Introduces, Facilitates, Explains

Listens

Knowledge, Communication, intrapersonal, Application

60

Reading

demonstration

Explains,

Monitors

Participates, Discusses

comprehension, Hands on experiment

20

Calculations

N/A

Explains,

Monitors

Participates, Discusses

Knowledge, Communication, Intrapersonal, Application

10

Results and conclusions

Keywords

Lists, Facilitates

Listens, Participates, Discusses

Knowledge, Communication, intrapersonal, Comprehension

Practical Session Plan


Title: Analysis of Microstrip Patch Antenna

Objectives: Mount & connect the set up of microstrip patch antenna to compute practical parameters & compare it with the standard parameters.

Aim: To analysis the Microstrip Patch antenna and find following parameters related to antenna

1) 2D Radiation Pattern

2) Return Loss

3) Gain in dB

4) Front to Back Ratio

5) Beamwidth

Apparatus: Antenna Trainer Kit, Half Wavelength Dipole antenna, Directional Coupler, coaxial connectors.

Theory:

1) Basic type of antenna: Microstrip Patch

2) Antenna Subtype of antenna: Square Microstrip Patch

3) Antenna Operating frequency of antenna: 1.25 GHz

4) Theoretical Information

A patch antenna is a narrowband, wide-beam antenna fabricated by etching the antenna element pattern in metal trace bonded to an insulating dielectric substrate, such as a printed circuit board, with a continuous metal layer bonded to the opposite side of the substrate which forms a ground plane. Common microstrip antenna shapes are square, rectangular, circular and elliptical, but any continuous shape is possible. Some patch antennas do not use a dielectric substrate and instead made of a metal patch mounted above a ground plane using dielectric spacers; the resulting structure is less rugged but has a wider bandwidth.

Fig. 1: Microstrip Antenna Top and side view

Because such antennas have a very low profile, are mechanically rugged and can be shaped to conform to the curving skin of a vehicle, they are often mounted on the exterior of aircraft and spacecraft, or are incorporated into mobile radio communications devices. Microstrip antennas are relatively inexpensive to manufacture and design because of the simple 2-dimensional physical geometry. They are usually employed at UHF and higher frequencies because the size of the antenna is directly tied to the wavelength at the resonant frequency.

A single patch antenna provides a maximum directive gain of around 6-9 dBi. It is relatively easy to print an array of patches on a single (large) substrate using lithographic techniques. Patch arrays can provide much higher gains than a single patch at little additional cost; matching and phase adjustment can be performed with printed microstrip feed structures, again in the same operations that form the radiating patches. The ability to create high gain arrays in a low-profile antenna is one reason that patch arrays are common on airplanes and in other military applications.

Procedure:

1) Mount the Microstrip Patch antenna on receiver stand of antenna trainer kit; connect a coaxial cable between antenna and input section of transreceiver meter.

2) Mount Yagi-Uda antenna on stand of transmitter stand of antenna trainer kit, connect a coaxial cable between antenna and output section of transreceiver meter.

3) Apply a frequency of 1250 MHz (1.25 GHz) to transmitter antenna by varying knob on transreceiver meter.

4) Take the reading of field strength of receiver antenna, which indicated on transreceiver meter, note this reading as first reading for angle of 0 degree.

5) Rotate the receiver antenna mount with an increment of 5 degree and take respective readings.

6) Plot the 2D radiation pattern of antenna using observed readings.

7) To find VSWR of antenna connect the coaxial cable from antenna under test to input terminal of directional coupler,

8) Output terminal of directional coupler is connected to input terminal of transreceiver meter, and common terminal is connected to input terminal of transreceiver meter.

9) Press VSWR button on transreceiver meter you get value of Vi (incident Voltage).

10) Now reverse the direction of input & output of directional coupler and press VSWR button you get value of Vr (Reflected voltage) & VSWR.

Observations:

The observation table of reading obtained is:

Angle

(Degree)

Field Strength

Angle

(Degree)

Field Strength

Angle

(Degree)

Field Strength

0

130

260

5

135

265

10

140

270

15

145

275

20

150

280

25

155

285

30

160

290

35

165

295

40

170

300

45

175

305

50

180

310

55

185

315

60

190

320

65

195

325

70

200

330

75

205

335

80

210

340

85

215

345

90

220

350

95

225

355

100

230

105

235

110

240

115

245

120

250

125

255

Sample Calculations:

1) VSWR = Vi / Vr =

2) Front to Back ratio = maximum reading / minimum reading =

3) Return Loss = (VSWR-1) / (VSWR+1) =

4) Gain of antenna = ( Maximum reading of AUT â€" Maximum reading of dipole antenna) +7=

5) Beamwidth can be calculated by observing 2D radiation pattern.

HPBW =

FNBW =

Radiation Pattern:

Results:

1) VSWR =

2) Front to Back ratio =

3) Return Loss =

4) Gain of antenna =

5) HPBW =

FNBW =

Conclusion:

The Microstrip Patch antenna was analyzed on the antenna trainer kit. Field Strength of various angle were obtained and radiation pattern were plotted for same.

Upon completion of experiment students will be able to:

Students will able to demonstrate the radiation pattern of the Micro strip patch antenna, compute the performance parameters practically and compare the performance parameters with the standard parameters

Oral Question Bank

Theory Question Bank

Q. No

Description

1

Microstrip patch antennas are used for which frequency range?

2

List the applications of microstrip patch antenna?

3

What is the main drawback of microstrip patch antenna?

4

Which type of polarization is achieved with microstrip patch antenna?

5

How to increase bandwidth of microstrip patch antenna?

6

How to increase the directivity of microstrip patch antenna?

7

Which different types of shapes can be used for the patch of microstrip patch antenna? Which shape is generally preferred?

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