Name of the College : Noorul Islam College of Engineering
University : Anna University
Degree : B.E
Department : Electronics and Communication Engineering
Subject Code/Name : EC 1305 – Transmission Lines & Wave Guides
Year : III
Semester : V
Document Type : Question Bank
Website : niceindia.com
Download :https://www.pdfquestion.in/uploads/ni…WAVEGUIDES.pdf
NICE Transmission Lines & Wave Guides Question Paper
Unit I-Transmission Line Theory :
1.Define the line parameters? :
The parameters of a transmission line are :
** Resistance (R) is defined as the loop resistance per unit length of the wire. Its unit is ohm/Km
** Inductance (L) is defined as the loop inductance per unit length of the wire. Its unit is Henry/Km
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** Capacitance (C) is defined as the loop capacitance per unit length of the wire. Its unit is Farad/Km
** Conductance (G) is defined as the loop conductance per unit length of the wire. Its unit is mho/Km
2. What are the secondary constants of a line? : Why the line parameters are called distributed elements?:
The secondary constants of a line are :
** Characteristic Impedance
** Propagation Constant
Since the line constants R, L, C, G are distributed through the entire length of the line, they are called as distributed elements. They are also called as primary constants.
3.Define Characteristic impedance :
Characteristic impedance is the impedance measured at the sending end of the line. It is given by Z0 = Z/Y,where
Z = R + jL is the series impedance
Y = G + jC is the shunt admittance
4. Define Propagation constant :
Propagation constant is defined as the natural logarithm of the ratio of the sending end current or voltage to the receiving end current or voltage of the line. It gives the manner in the wave is propagated along a line and specifies the variation of voltage and current in the line as a function of distance.
5.What is a finite line? : Write down the significance of this line?:
A finite line is a line having a finite length on the line. It is a line, which is terminated, in its characteristic impedance (ZR=Z0), so the input impedance of the finite line is equal to the characteristic impedance (Zs=Z0).
6.What is an infinite line? :
An infinite line is a line in which the length of the transmission line is infinite. A finite line, which is terminated in its characteristic impedance, is termed as infinite line. So for an infinite line, the input impedance is equivalent to the characteristic impedance.
8.What are the types of line distortions? :
The distortions occurring in the transmission line are called waveform distortion or line distortion. Waveform distortion is of two types :
a) Frequency distortion
b) Phase or Delay Distortion.
9.How frequency distortion occurs in a line? :
When a signal having many frequency components are transmitted along the line, all the frequencies will not have equal attenuation and hence the received end waveform will not be identical with the input waveform at the sending end because each frequency is having different attenuation. This type of distortion is called frequency distortion.
10.How to avoid the frequency distortion that occurs in the line? :
In order to reduce frequency distortion occurring in the line, a) The attenuation constant should be made independent of frequency. b) By using equalizers at the line terminals which minimize the frequency distortion. Equalisers are networks whose frequency and phase characteristics are adjusted to be inverse to those of the lines, which result in a uniform frequency response over the desired frequency band, and hence the attenuation is equal for all the frequencies.
11.What is delay distortion? :
When a signal having many frequency components are transmitted along the line, all the frequencies will not have same time of transmission, some frequencies being delayed more than others. So the received end waveform will not be identical with the input waveform at the sending end because some frequency components will be delayed more than those of other frequencies. This type of distortion is called phase or delay distortion.
12. How to avoid the frequency distortion that occurs in the line? :
In order to reduce frequency distortion occurring in the line,
a) The phase constant should be made dependent of frequency.
b) The velocity of propagation is independent of frequency.
c) By using equalizers at the line terminals which minimize the frequency distortion. Equalizers are networks whose frequency and phase characteristics are adjusted to be inverse to those of the lines, which result in a uniform frequency response over the desired frequency band, and hence the phase is equal for all the frequencies.
13.What is a distortion less line? : What is the condition for a distortion less line?:
A line, which has neither frequency distortion nor phase distortion is called a distortion less line. The condition for a distortion less line is RC=LG. Also,
a) The attenuation constant should be made independent of frequency.
b) The phase constant should be made dependent of frequency.
d) The velocity of propagation is independent of frequency.
14.What is the drawback of using ordinary telephone cables? :
In ordinary telephone cables, the wires are insulated with paper and twisted in pairs, therefore there will not be flux linkage between the wires, which results in negligible inductance, and conductance. If this is the case, the there occurs frequency and phase distortion in the line.
15.How the telephone line can be made a distortion less line? :
For the telephone cable to be distortion less line, the inductance value should be increased by placing lumped inductors along the line.