Previous year question paper for NFTL (Diploma Electronics and Communication Engineering 4th)

Network Filters and Transmission Lines

Previous year question paper with solutions for Network Filters and Transmission Lines from 2014 to 2018

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1. Networks (14 hrs)

a) Two port (four terminals) network: Basic concepts of the following terms:

- Symmetrical and asymmetrical networks: Balanced and unbalanced network;

T-network, Л network, Ladder network; Lattice network; L-network and Bridge


b) Symmetrical Network:

- Concept and significance of the terms characteristic impedance, propagation constant,

attenuation constant, phase shift constant and insertion loss of T-network and

Л Network

c) Asymmetrical Network

- Concept and significance of iterative impedance, image impedance, image transfer

constant and insertion loss. - The half section (L-section); symmetrical T and Л sections into half sections

2. Attenuators (05 hrs)

a) Units of attenuation (Decibels and Nepers): General characteristics of attenuators

b) Analysis and design of simple attenuator of following types; Symmetrical T and Л type,

L type.

3. Filters (13 hrs)

a) Brief idea of the use of filter networks in different communication systems, concept of low

pass, high pass, band pass and band stop filters.

b) Prototype Filter Section:


- Impedance characteristics vs frequency characteristics of a low and high pass filter

and their significance

- Attenuation Vs frequency; Phase shift Vs frequency, characteristics impedance vs

frequency of T and Л filters and their significance

- Simple design problems of prototype low pass filter. c) M-Derived Filter Sections

Limitation of prototype filters, need of m-derived filters

d) Crystal Filters

Crystal and its equivalent circuits, special properties of piezoelectric filters and their use

e) Active Filters

Basic concept of active filters and their comparison with passive filters.

4. Transmission Lines (16 hrs)

a) Transmission Lines, their types and applications.

b) Distributed constants, T and Л representation of transmission line section.

c) Definition of characteristic impedance, propagation constant, attenuation constant and

phase shift constant.

d) Concept of infinite line

e) Condition for minimum distortion and minimum attenuation of signal on-the-line and

introduction to loading methods.

f) Concept of reflection and standing waves, definition of reflection coefficient, SWR & VSWR

and their relation (no derivation).

g) Transmission line equation, expression for voltage, current and impedance at a point on

the line.

h) Concept of transmission lines at high frequencies.

i) Introduction to stubs. (single, open and short stubs).