Jawaharlal Nehru Technological University Kakinada 2007 B.Tech Electronics and Communications Engineering ANTENNAS AND WAVE PROPAGATION - Question Paper

Telematics)
Time: three hours Max Marks: 80
ans any 5 ques.
All ques. carry equal marks
? ? ? ? ?
1. (a) Distinguish ranging from Directive Gain and Power Gain.
(b) An antenna has a radiation resistance of 73 ohms and a lossy resistance of 7
ohms. If the power gain is 20, compute the directivity and the efficiency of
the antenna. [8+8]
2. (a) Derive an expression for radiance resistance of current element starting from
the expression for radiation fields.
(b) Prove that the impedance of an isolated antenna when used for receiving is
identical as when used for transmitting. [8+8]
3. (a) In order to scan the beam of a linear array to 300 off broadside. compute the
inner element phase shift needed if the elements are spaced at three cms and the
frequency is 64 KHz.
(b) elaborate linear arrays. Compare Broadside array and End fire array. [8+8]
4. (a) Derive an expression for electric field of a Non Resonant antenna of length ‘l’
carrying current.
(b) Sketch and discuss the constructional features of a Helical Antenna. [10+6]
5. (a) What is a Parasitic Element? define the use of various kinds of parasites
in TV receiving antennas.
(b) Derive an expression for aperture field distribution of a parabolidal reflector.
[8+8]
6. (a) define the method of measuring the gain and radiation trend of an an-
tenna.
(b) A standard gain horn antenna with a power gain of 12.5, is used to measure the
gain of a large directional antenna by comparison method. The test antenna
is connected to the receiver and an attenuator adjusted to 23dB in order to
have the identical receiver output. obtain out the gain of the large antenna. [8+8]
7. (a) describe MUF and Critical frequency. Derive the expressions for the identical.
What is Secant law?
(b) define the Ground wave propagation. [8+8]
8. (a) Derive the field strength of tropospheric wave.
1 of 2
Code No: R05310403 Set No. 2
(b) provide an account of effect of earths imperfections and roughness. [8+8]
? ? ? ? ?
2 of 2
Code No: R05310403 Set No. 3
III B.Tech I Semester Regular Examinations, November 2007
ANTENNAS AND WAVE PROPAGATION
( Common to Electronics & Communication Engineering and Electronics &

Earning:   Approval pending.