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END TERM EXAMINATION
FIFTH SEMESTER [B.TECH.] JAN 2024
Programme: B.TECH. Maximum Marks: 75
Paper Code: ECC-309 Duration: 03:00 Hrs
Subject: TRANSMISSION LINES, WAVEGUIDES & ANTENNA DESIGN
Note: Attempt any five questions including Q.No 1 which is compulsory. Select one question from each unit.
Q.1. (a) Define dominant, degenerate and evanescent modes. (3)
(b) Write wave equations for voltage and current for a transmission line. (3)
(c) Define loaded and unloaded Q for series and parallel resonance circuits. (3)
(d) Define the following with respect to antenna: (3)
i) Major lobe & Minor lobe
ii) Antenna efficiency & Radiation Efficiency
iii) Directivity & Gain of an antenna
(e) What is fringing in Microstrip transmission line? How to account for this in the microstrip (3)
transmission line?
Unit-I
Q.2. (a) Derive impedance for shorted and open circuited transmission line. (5)
(b) A telephone line has R=30Ω/km, L=100 mH/km, G=0 and C=20μF/km. At f=1 KHz, obtain (5)
i) Characteristics impedance of the line
ii) Propagation Constant
iii) Phase Velocity
(c) Write short note on the following (any two): (5)
i) Characteristic Impedance
ii) Voltage standing wave ratio
iii) Reflection Coefficient
Q.3. (a) Explain the design of the Smith Chart. Also explain how to find impedance at the distance ‘l’ (5)
from the load using Smith Chart.
(b) A 600Ω lossless transmission line is fed by 50Ω generator. If the line is 200m long (5)
terminated by a load of 500Ω. Determine in dB,
i) Reflection Loss
ii) Transmission Loss
iii) Return Loss
(c) Write short note on the following (any two): (5)
i) Quarter wave transformer
ii) Stub matching
iii) Microstrip Transmission Line
Unit-II
Q.4. (a) Derive field components of TE waves in rectangular waveguide. Also deduce instantaneous (10)
field expressions for TE01 mode.
(b) In a rectangular waveguide for which a=1.5cm, b=0.8cm, σ=0, μ=μ 0 and ϵ=4ϵ0. (5)
( ) ( ) ( )
Determine:
i) The mode of operation
ii) The cutoff frequency
iii) The phase constant
iv) The propagation constant
v) The internal wave impedance
Q.5. (a) Derive field components of TE waves in circular waveguide. Show dominant mode in (10)
circular waveguide.
(b) An air-filled circular waveguide having an inner radius of 0.8cm is excited in dominant mode (5)
at 10 GHz. Find the cut off frequency of dominant mode, guide wavelength and bandwidth
for operating in dominant mode.
Unit-III
Q.6. (a) Derive an expression for unloaded Q of a transmission line resonator consisting of a short- (5)
circuited transmission line λ/2 long.
(b) A circular cavity resonator with d=2a is to be designed to resonate at 5.0 GHz in the TE 011 (5)
mode. If the cavity is made from copper and is Teflon filled (ϵr=2.1, tanδ=0.0004), find its
dimension and unloaded Q.
(c) Compute the resonant frequency of a cylindrical resonator with ϵr=10.8, 2a=11.71mm and (5)
L=2.14mm.
Q.7. (a) Derive the unloaded Q for the TM111 mode of a rectangular cavity, assuming lossy (5)
conducting walls and lossless dielectric.
(b) A rectangular cavity resonator is constructed from 3.0 cm length of aluminum X-band (5)
waveguide. The cavity is air filled. Find the resonant frequency and unloaded Q of the TE 101
and TE102 resonant modes.
(c) Explain in detail development of gap-coupled microstrip resonator. (5)
Unit-IV
Q.8. (a) Define and derive power spectral density of an antenna. Establish relation between radiation (7)
intensity and total power radiated by an antenna.
(b) Derive Friis transmission equation for transmitting and receiving antennas. (5)
(c) An antenna has a normalized radiation intensity given by U(θ)=cos2(3θ) for 0≤θ≤Π/2 and (3)
0≤φ≤2Π. Find HPBW and FNBW in degrees.
Q.9. (a) Obtain the expression for Electric Field Intensity and Magnetic Field Intensity due to (10)
magnetic vector potential A for electric current source J only. Write expressions for ⃗⃗⃗ and ⃗
for Magnetic current source ⃗⃗ using duality theorem.
(b) State Reciprocity theorem for antennas in differential and integral form. (5)
