Code No: V3118/R07

Set No: 1

III B.Tech I Semester Regular & Supplementary Examinations, November 2011 ANTENNAS AND WAVE PROPAGATION (Electronics and Communications Engineering) Time: 3 Hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ***** 1. a) Define the terms Radiation intensity, Gain, Resolution and Beam efficiency b) The field pattern of an antenna is given by En = (Sin / ) i) Plot the normalized power pattern. ii) Estimate the main beam efficiency of the antenna. [8+8] 2. a) State the Reciprocity Theorem for antennas? Prove that the Self Impedance of an antenna in transmitting and receiving mode is same. b) Define directivity, obtain the directivity of an isotropic antenna, short dipole and Half-wave Dipole. [8+8] 3. a) How a unidirectional pattern is obtained in an end fire array. Explain? b) What are the advantages and disadvantages of binomial array?

ar

1 of 1

.o

rg

[8+8]

an

5. a) Derive an expression for the gain of a 900 corner reflector. b) Explain the principle and working of Yagi Antenna.

di

4. a) Explain in detail the constructional features of helical antenna? b) Compare the requirements and radiation characteristics of resonant and non resonant radiators [8+8]

St

[8+8]

U

6. a) What is Zoning? What are its advantages? b) Discuss the applications of Horn Antenna. Sketch the sectoral horns. 7. a) Explain the following: i) Ground Wave ii) Space Wave iii) Surface Wave b) Discuss the characteristics of ionospheric layer

[8+8]

[10+6]

8. A communication link is to be established between two stations using half wave-length antenna for maximum directive gain. Transmitter power is 1 KW, frequency of operation is 100 MHz and distance between transmitter and receiver is 100 Km. what is the maximum power received by receiver? Explain and derive the formulas used. [16] *****

For more Visit: www.UandiStar.org

Code No: V3118/R07

Set No: 2

III B.Tech I Semester Regular & Supplementary Examinations, November 2011 ANTENNAS AND WAVE PROPAGATION (Electronics and Communications Engineering) Time: 3 Hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ***** 1. a) As related to antennas, define and explain the following terms: i ) Radiation Resistance ii) Effective Area iii) Effective Length iv) Efficiency b) Find the effective aperture of an isotropic antenna operating at a wavelength of 10-2 m, deriving its directivity. [8+8] 2. a) Give the expression for electric field due to current element. Find the distance from a radiating element such that Radiation and Induction fields are equal with necessary assumptions. b) What is short magnetic Di-pole? How is it realized? [10+6] 3. a) Derive an expression for the far field pattern of an array with ‘n’ identical isotropic point sources arranged in a line and spaced a distance ‘d’ apart. b) Explain the principle of pattern multiplication. [10+6] 4. a) Sketch and explain the constructional features of Helical Antenna. b) Sketch and explain the basic set up for V-antenna and plot the pattern.

ar

.o

rg

7. a) Write short notes on “Ground wave propagation and effective of earth” b) In case of ionosphere, explain D, E&F layers. 8. a) Discuss Duct Propagation dwell on causes and effects. b) Explain the bending of signals due to earths curvature. How is it useful for propagation? *****

U

5. a) Design Yagi Uda antenna of six elements to provide a gain of 12dB if the operating frequency is 200MHz b) Explain with suitable sketches perpendicular mode of radiation in helical antenna. [8+8] 6. Describe the methods for measuring the below parameters for an antenna a) Gain b) Directivity with a neat block diagram [8+8]

an

di

St

[8+8]

[8+8]

[8+8]

1 of 1

For more Visit: www.UandiStar.org

Code No: V3118/R07

Set No: 3

III B.Tech I Semester Regular & Supplementary Examinations, November 2011 ANTENNAS...