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.       Which one of the following is a passive element?

 

(A) A BJT. (B) An Inductor.

(C) A FET. (D) An Op-amp.

b. Millman theorem yields

(A)  equivalent resistance of the circuit.

(B)  equivalent voltage source.

(C)  equivalent voltage OR current source.

(D) value of current in milliamperes input to a circuit from a voltage

source.

c. The z-parameters of the shown T-network at Fig.1 are given by
 
 


(A)    5, 8, 12, 0

(B)    13, 8, 8, 20

(C)    8, 20, 13, 12

(D)    5, 8, 8, 12

 

 

 

 

d.      To a highly inductive circuit, a small capacitance is added in series. The angle between voltage and current will

 

(A) decrease. (B) increase.

(C) remain nearly the same. (D) become indeterminant.

 

e. The equivalent inductance of Fig.2 at terminals is equal to
 

(A)    

(B)    

(C)

(D)

 

 

 

 

f. The characteristic impedances of a transmission line is given by, (where R, L, G, C are the unit length parameters)

 

(A) (B)

(C) (D)

 
 
g. The relation between for the given symmetrical lattice attenuator shown in Fig.3 is

 

(A)    

(B)    

(C)    

(D)   

 

 

 

h. If Laplace transform of x(t) = X(s), then Laplace transform of x(t-t0) is given by

 

(A)   (B)

(C) (D)

PART I

Answer any THREE Questions. Each question carries 14 marks.

 

Q.2 a. The current in a conductor varies according to the equation

Find the total charge in coulomb that passes through the conductor. (7)

 

b. A current I = 10t A flows in a condenser C of value 10 . Calculate the voltage, charge and energy stored in the capacitor at time t= 1 sec. (7)

 

Q.3 a. Define Laplace transform of a time function x(t) u(t). Determine Laplace transforms for

(i) (the impulse function)

(ii) u(t) (the unit step function)

(iii) tn eat, n +ve integer (7)

b.      Find the Inverse Laplace transform for

(i)

(ii) (3+4)

 

Q.4 For the circuit shown, at Fig.4 the switch K is closed at t=0. Initially the circuit is fully dead (zero current and no charge on C). Obtain complete particular solution for the current i(t). (14)
 
 

 

 

 

 

 

 

 


Q.5 a. Derive necessary and sufficient condition for maximum power transfer from a voltage source, with source impedance , to a load . What is the value of the power transferred in this case? (7)

 
 
b. By using Nortons theorem, find the current in the load resistor for the circuit shown in Fig. 5. (7)

 

 

 

 

 

 

 

Q.6 a. Differentiate between Bilateral and Unilateral elements with suitable examples. (7)

 

b. Determine the ABCD parameters for the -network shown at Fig.6. Is this network bilateral or not? Explain. (7)
 
 

 

 

 

 

 


PART II

Answer any THREE Questions. Each question carries 14 marks.

Q.7 a. Determine the relationship between y-parameters and ABCD parameter for 2-Port networks. By using these relations determine y-parameters of circuit given in Fig.7 and then deduce its ABCD parameters. (7)
 
 

 

 

 

 

 

 

 


b. What is the significance of poles and zeros in network functions. What is the criteria of stability of a network? For the transform current , plot its poles and zeros in s-plane and hence obtain the time domain response. (7)

 

Q.8 Solve the differential equation given below and determine the steady state solutions.

(i)

(ii) (7+7)
 
Q.9 Determine the condition for resonance for the parallel circuit as shown in Fig.8. Determine its

(i) resonant frequency (3)

(ii) impedance z (j) at (3)

(iii) half power bandwidth (4)

(iv) quality factor of the circuit. (4)

 

 

Q.10 a. For the case of distributed parameters, determine the expressions for:

(i) Characteristic impedance ()

(ii) Propagation constant ()

(iii) Attenuation and phase constants (7)

 

b. A transmission line is terminated by an impedance . Measurements 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 is 300 . Find the value of . (7)

 

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

(i)      Low-pass filter and its approximation/design.

(ii)     T and - attenuators.

(iii)    Single stub matching in transmission line.

(iv)   H-parameters, its relations with z-parameters and y-parameters. (2x7=14)