Code: D-07 Subject: NETWORK AND TRANSMISSION LINES

Time: 3 Hours Max. Marks: 100

NOTE: There are 11 Questions in all.

· Question 1 is compulsory and carries 16 marks. Answer to Q. 1. must be written in the space provided for it in the answer book supplied and nowhere else.

· Answer any THREE Questions each from Part I and Part II. Each of these questions carries 14 marks.

· Any required data not explicitly given, may be suitably assumed and stated.

Q.1 Choose the correct or best alternative in the following: (2x8)

a. The following constitutes a bilateral element

(A) A resistor. (B) FET.

(C) Vacuum tube. (D) metal rectifier.

b. Voltages and in the given circuit are

(A) 20 volts each.

(B) 10 volts each.

(C) 16 volts, 4 volts.

(D) 4 volts, 16 volts.

c. Step response of series RC circuit with applied voltage V is of the form

(A) (B)

(C) (D)

d.

In the given circuit switch S is opened at time t=0, then is

(A) volt / sec.

(B) 100 volt / sec.

(C) volt / sec.

(D) 10 volt / sec.

e. In the circuit shown, maximum power will be transferred when

(A)

(B)

(C)

(D)

f. Voltage Standing Wave Ratio (VSWR) in terms of reflection coefficient is given by

(A) . (B) .

(C) . (D) .

g. For a 2-port network, the output short circuit current was measured with a 1V source at the input. The value of the current gives

(A) (B)

(C) (D)

h. . When i(t) is the unit step function, the value of v (t) in the steady state is given by

(A) . (B) 1.

(C) 0. (D) .

PART I

Answer any THREE Questions. Each question carries 14 marks.

Q.2 a. A 50 capacitor is initially charged to accumulate 100 C. One uncharged capacitor of 200F is connected across it in parallel. How much charge will be transferred? (7)

b. Define Laplace transform of a function f(t). Find the Laplace transforms for the functions (7)

Q.3 a. State and prove the Initial value theorem in Laplace transform domain. (3)

b. Determine the Inverse Laplace transform for the function . (4)

c.

Find i(t) in the circuit if the switch S is closed at t = 0 and the initial charge of 250 on the Capacitor C. (7)

Q.4 a. Explain the significance of causality, linearity and time invariance of a system. Why are they desirable? (4)

b. Obtain the conditions of maximum power transfer from a source to a load . What is the value of transferred power? (5)

c. State and prove the Millman’s theorem and its dual. Give its typical uses. (5)

Q.5 a. Define Z-parameters and Y-parameters of a 2-port network. Determine the relation between Z and Y-parameters. (7)

b. Find the Z-parameters for the 2-P network given in Fig 5 b and deduce h-parameters using the Z-parameters found above. (7)

Q.6 a. What importance do the poles and zeros of a network play? What is the condition that a network is stable? (4)

b. State whether or not the following functions are driving point immittances of LC network.

(i)

(ii) (6)

c. Voltage is applied to a series circuit containing resistor

R, inductor L and capacitor C. Obtain expression for the steady state response.

(4)

PART II

Answer any THREE Questions. Each question carries 14 marks.

Q.7 a. Starting from abinitio, derive the voltage and current equation of a transmission line with distributed per unit parameters L, C, R and G. Derive the values of

(i) Characteristic impedance

(ii) Propagation constant

(iii) Attenuation constant and phase constant (8)

b. Show that the input impedance at the sending end is for an infinite length of the transmission line. (3)

c. What is the input impedance at the sending end if the transmission line is loaded by a load ? (3)

Q.8 a. Define Voltage Standing Wave Ratio (VSWR) for the transmission line. How is VSWR connected with the reflection coefficient ? (7)

b. A transmission line is terminated by an impedance . Measurements taken on the line show that the standing wave minima are 105 cm apart and the first minimum is 30 cm from the load end of the line. The VSWR is 2.3 and . Find . (7)

Q.9 a. What are the commonly used filters? How do we define their passband and stopband. (6)

b. Design a constant-k high pass T and -section filter having cut-off frequency of 6 KHZ and nominal characteristic resistance . (8)

Q.10 a. What is an attenuator. What types of symmetrical attenuators are most popular. Explain, in detail, the design procedure of symmetrical T-attenuator. (7)

b. Design a symmetrical T-attenuator to give 60 dB and to work into a load of impedance. (7)

Q.11 Write short notes on any TWO of the following:

(i) Double stub matching in a transmission line.

(ii) Design of a maximally flat low-pass filter.

(iii) Parallel resonance circuit, its resonance frequency, dynamic resistance

(R_D) at resonance and Quality factor (Q).

(iv) Enunciation of Thevenin’s and Norton’s theorems. Their inter-

relation-ships and practical use be highlighted. (2x7=14)