VHDL Adavanced VHDL Arithmetic-Circuits

VHDL Concurrent-Statements

Counters

Flipflops

Logic-Circuits

Logic-Gates

Sequential-Statements

Shift-Registers

EXPERIMENT NO.5

Analysis of Parabolic Reflector

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 Parabolic Reflector

Objectives: Mount and set up the connections of Parabolic Reflector antenna to analyze the performance parameters

Aim:

1) To sketch the radiation pattern of Parabolic Reflector antenna

2) To compute gain ,beam width ,return loss & impedance of Parabolic Reflector antenna

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

Theory:

1) Basic type of antenna: Reflector antenna

2) Theoretical Information:

A parabolic antenna is an antenna that uses a parabolic reflector, a curved surface with the cross-sectional shape of a parabola, to direct the radio waves. The most common form is shaped like a dish and is popularly called a dish antenna or parabolic dish. The main advantage of a parabolic antenna is that it has high directivity. It functions similarly to a searchlight or flashlight reflector to direct the radio waves in a narrow beam, or receive radio waves from one particular direction only.

Parabolic antennas have some of the highest gains, that is they can produce the narrowest beam width, of any antenna type. In order to achieve narrow beamwidths, the parabolic reflector must be much larger than the wavelength of the radio waves used, so parabolic antennas are used in the high frequency part of the radio spectrum, at UHF and microwave (SHF) frequencies, at which the wavelengths are small enough that conveniently-sized reflectors can be used.

Fig.1: Parabolic Reflector

Parabolic antennas are used as high-gain antennas for point-to-point communications, in applications such as microwave relay links that carry telephone and television signals between nearby cities, wireless WAN/LAN links for data communications, satellite communications and spacecraft communication antennas. They are also used in radio telescopes.

The other large use of parabolic antennas is for radar antennas, in which there is a need to transmit a narrow beam of radio waves to locate objects like ships, airplanes, and guided missiles.

Procedure

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

2) Mount Half wavelength dipole 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

By observing the radiation pattern of antenna & obtained readings, we have value of maximum & minimum reading, value of Vi & V r, with these data we have to calculate antenna parameter as:

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) Beam width can be calculated by observing 2D radiation pattern.

HPBW =

FNBW =

Radiation Pattern:

Result:

1) VSWR =

2) Front to Back ratio =

3) Return Loss =

4) Gain of antenna =

5) HPBW =

FNBW =

Conclusion: The parabolic reflector antenna was analyzed on antenna trainer kit. Field Strength of various angle were obtained and radiation pattern were plotted for same: highly directional having maximum lobe in one direction.

Upon completion of experiment students will be able to:

Students will able to demonstrate the radiation pattern of the Parabolic Reflector 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

Explain parabolic reflector antenna.

2

What are the different types of parabolic reflectors?

3

What are factors affecting parabolic reflector antenna gain

4

Parabolic reflectors are generally used for which frequency range?

5

List the formulae for

a) First null beam width

b) HPBW

c) Directivity

Of parabolic reflector

6

List different feeds used for parabolic reflector.

7

What is the advantage of cassegrain feed?

8

What is the main advantage of parabolic reflector antenna?

9

Draw the radiation pattern for parabolic reflector antenna?

FaceBook
Likes
Additonal Information