Saturday, November 19, 2016

EC6503 Transmission Lines and Waveguides Nov Dec 2016 Important Questions

Important questions for Nov Dec 2016 EC6503 Transmission Lines and Waveguides examinations conducting by Anna University Chennai
05th Semester / III Year
Electronics and Communication Engineering
EC6503 Transmission Lines and Waveguides
(Regulation 2013)
Nov Dec 2016 Important Questions

Important 16 Marks Questions with answers (All five units) are listed for EC6503 Transmission Lines and Waveguides subject

1. i) Describe the general transmission line equation for the voltage and current at any point on a
transmission line.(12)
ii) Illustrate Delay or phase distortion (4)

2.  i) Discuss in detail about inductance loading of telephone cables and derive the attenuation constant, phase constant and velocity of signal transmission for the uniformly loaded cable.(8)
ii) Explain in detail about the reflection on a line not terminated in its characteristic impedance.(8)

3. i) Discuss the types of loading of lines.(8)
ii) Write a short note on reflection factor and reflection loss and give expressions.(8)

4. i) Explain in detail about the waveform distortion and also derive the waveform distortion and also
derive the condition for distortion less line. (10)
ii) Derive the expression for open and short circuited impedance. (6)

5. i) A transmission line has the following per unit length parameters: L = 0.1μH, R =5 Ω, C = 300 pF and G = 0.01 ohm. Calculate the Propagation constant and characteristic impedance at 500 MHz.(8)
ii) A telephone cable 64Km long has a resistance of 13Ω/Km and a capacitance of 0.008 µF/Km. Calculate the attenuation constant, velocity and wavelength of the line at 1000Hz.(8)

6. i) Derive the expressions for voltage and current at any point on the radio frequency line terminated in ZR. Obtain the expressions for the same for different receiving end conditions. Support with the graph of voltage and current on a line for all conditions. (8)
ii) Explain briefly about the power and impedance measurement on lines.(8)

7. i) Explain the parameters of open wire line and co-axial at RF. Mention the standard assumptions
made for radio frequency line. Give condition for dissipation less.(8)
ii) Enumerate the Line constants for zero dissipation.(8)

8. i) The VSWR measured on UHF transmission line at a frequency of 300MHz found to be 2.if the
distance between load and voltage minimum is 0.8m, solve the normalized load impedance.(8)
ii) A lossless transmission line with Z0 = 75 ohm and of electrical length l = 0.3λ is terminated with
load impedance of ZR = (40+j20)Ω. Determine the reflection coefficient at load, SWR of line, input impedance of the line.(8)

9. i) Analyse the expressions for the input impedance of the dissipation less line. Deduce the input impedance of open and short circuited dissipation less line. (8)
 ii) Discuss about Reflection losses on the unmatched line and make a relation between power absorbed by the load and power transmitted by the source as a function S. (8)

10. i) Derive the voltage and currents at any point on the dissipation less line along with incident and
reflected voltage wave phasor diagrams which should satisfy the conditions such as open circuit,
short circuit, RR=R0. (10)
ii) Explain standing waves with neat diagram. (6)

11. i) Show the technique of double stub matching with neat diagram. (8)
ii) A lossless line with ZO =70Ω is terminated with ZR =115-80jΩ. Wavelength of transmission is 2.5
λ. Using smith chart find SWR, K, input impedance and input admittance. (8)

12. i) Consider a line of RO = 55 ohms terminated in 115+j75 ohms. If the total length of the line is
1.183λ, find the VSWR, input impedance and admittance (8)
ii) Find the input impedance and admittance of a co-axial line having RO = 95 ohms and the line is
20m long short circuited at far end operated at 10MHz. (8)

13.  i) What is the procedure for double stub matching on a transmission line with an example.(8)
ii) Write notes on Eight wave line and half wave line. (8)

14. Explain the transmission line circle diagram by deriving the expression for constant S and constant βs circle. (16)

15. A transmission line is terminated in ZL. Measurements indicate that the standing wave minima are 102 cm apart and that the last minimum is 35 cm from the load end of the line. The value of standing wave ratio is 2.4 and R0 = 250Ω. Determine frequency, wavelength, Real and reactive components of the terminating impedance. Also Verify the results obtained from equations using the smith chart.(16)

16. i) Show the expression for the characteristics impedance of symmetrical T and Π section networks. (6)
ii) How would you explain the properties of symmetrical network in terms of characteristic impedance and propagation constant (6)
iii) Bring out the expression of attenuation in Neper and Decibel (4)

17. i) Draw and Show the design and operation of m derived low pass filter with necessary equations
and diagrams (8)
ii) Draw and Show the design and operation of m derived high pass filter with necessary equations
and diagrams (8)

18. i) What do you mean by composite filter? Discuss its construction, design and characteristics
briefly (8)
ii) Find the characteristics impedance and propagation constant of the symmetrical T network whose series arm is 50 ohms and shunt arm is 5000 ohms. (8)

19. i) How would you design a high pass filter having a cutoff frequency of 1 KHz with a load resistance of 600Ω. (6)
ii) Examine and design an m-derived low pass filter to work into load of 400Ω with cut off frequency at 1KHz and resonant frequency 1100Hz (10)

20. Develop a composite High pass filter to operate into the load of 600Ω and have a cutoff frequency of 1.2 KHz. The filter is have one constant k section, one m derived section with f∞ =1.1 KHz and suitably terminated half section.

21. (i) Discuss the principle of operation and applications of resonant cavities (10)
(ii) Explain the excitation of various modes in rectangular cavities (6)

22. (i) Derive the field component of a Transverse Electric wave in rectangular wave guides. (8)
(ii) Derive the expression of wave impedance of TE, TM and TEM wave between a pair of perfectly
conducting planes. (8)

23. A pair of perfectly conducting plates is separated by 10 cm in air and carries a signal frequency of 6 GHz in TE1 mode. Find Cut-off frequency, Angle of incidence on planes, Phase velocity, group velocity, Phase constant, Cut-off wavelength, characteristic wave impedance, and wavelength along guiding walls. Is it possible to propagate TE3 mode. (16)

24. (i) Explain about bessel functions of first and second kind and state its properties (10)
(i) A rectangular cavity resonator excited by TE101 mode at 20GHz has dimensions a = 2cm, b=1cm.
Calculate the length of the cavity (6)

25. A rectangular air filled copper waveguide with dimension 0.9 inch x 0.4 inch cross section and 12 inch length is propagated at 9.2 GHz with a dominant mode. Find the cutoff frequency, Guide wavelength, Phase velocity, characteristic impedance and the loss. (16)
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