Code: D-07                                              Subject: NETWORK AND TRANSMISSION LINES

Time: 3 Hours                                                                                                     Max. Marks: 100

NOTE: There are 9 Questions in all.

· Question 1 is compulsory and carries 20 marks. Answer to Q. 1. must be written in the space provided for it in the answer book supplied and nowhere else.

· Out of the remaining EIGHT Questions answer any FIVE Questions. Each question carries 16 marks.

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

Q.1       Choose the correct or best alternative in the following:                                         (2x10)

a. An RLC series circuit is said to be inductive if

(A) (B)

(C) (D) 

b. Laplace transform of an unit impulse function is given by

(A) 1                                                  (B)  -1

(C) (D)

             c.   A function  will have a zero at

(A) s = ± j4                                        (B)  Anywhere on the s-plane.

(C)  On the imaginary axis.                   (D)  On the origin.

             d.   For a two port reciprocal network, the three transmission parameters are given by A = 4, B = 7 and C = 5.  The value of D is equal to

(A)  8.5                                              (B)  9

(C)  9.5                                              (D)  8

             e.   Higher the value of Q of a series circuit

(A) Sharper is its resonance.               (B)  Greater is its bandwidth.

(C)  Broader is its resonant curve.        (D)  Narrower is its bandwidth.

             f.    An ideal filter should have

(A) Zero attenuation in the pass band.

(B) Zero attenuation in the attenuation band.

(C) Infinite attenuation in the pass band.   

(D) Infinite attenuation in the attenuation band.

             g.   For an m-derived high pass filter, the cutoff frequency is 4KHz and the filter has an infinite attenuation at 3.6 KHz, the value of m is

(A) 0.436                                           (B)  4.36

(C)  0.34                                             (D)  0.6

             h.   If  and , the characteristic impedance is

(A) (B)

(C) (D)

             i.    The reflection coefficient of a line is .  The line is

(A) Open circuited.                             (B) Short circuited.

(C) Terminated in .                         (D) Of infinite length.

             j.    If a transmission line of length less than  is short circuited, it behaves as

(A)  Pure capacitive reactance.            (B)  Series resonant circuit.

(C)  Parallel resonant circuit.                (D)  Pure inductive reactance.

Answer any FIVE Questions out of EIGHT Questions.

Each question carries 16 marks.

Q.2     a.   Define an ideal voltage source and an ideal current source.                              (2+2)

             b.   Calculate the voltage across the inductor of 2 Henry and the charge in the inductor at time t = 1 sec for the variation of the current as shown in the Fig.1.                                                                    (4)

             c.   A 60 Hz sinusoidal voltage V = 100 sin is applied to a series RL circuit.  Given , and L = 0.01H, find the steady state current and its phase angle.                                                      (8)

Q.3     a.   Find the Laplace transform of the functions:                                                            

(i)  u (t).                                          (ii)   u (t).                                   (4)

             b.   Using partial fraction method, obtain the inverse Laplace transform of

(4)

c.   A capacitor of  which is charged initially to 10 V is connected to resistance of 10 K and is allowed to discharge through the resistor by closing of a switch K at t = 0.  Find the expression for the discharging current.                                                                                                              (8)

Q.4     a.   State the final value theorem and find the final value of the function where the laplace transform is  .                                    (2+3)

b.   A symmetric T section has an impedance of  in each series arm and an impedance of  in each shunt arm.  Find the characteristic impedance and propagation constant of the network.      (5)

c.   Explain how a quarter wave transformer is used for impedance matching.            (6)

Q.5     a.   State Thevenin’s theorem.  Using Thevenin’s, find the current through  resistor as shown in the Fig. 3 below.                                                 (8)

     b.   State the superposition theorem. Using this theorem find the voltage across the  resistor.                                                                     (8)

  Q.6     a. Define ABCD parameters of a two-port network.  Derive the condition of reciprocity and symmetry in ABCD parameters of a two-port network.                                                         (8)

             b.   Calculate the driving point admittance of the network shown in the Fig.5.             (8)

Q.7     a.   A sinusoidal voltage of rms value 20V and frequency equal to frequency of resonance is applied to a series RLC circuit having resistance , inductance L = 0.05H and capacitance .  Calculate the value of current and voltages across R, L and C.                                           (8)

b.   Two coupled coils have a coefficient of coupling, k = 0.9.  Find the mutual inductance , and the turns ratio (n). (4)

c.   Explain how double tuned circuits are used in radio receivers.                             (4)

Q.8     a.   State the types of distortions in a transmission line.  Derive the conditions to eliminate the two types of distortions.                                           (8)

             b.   A generator of 1V, 1000Hz supplies power to 1000 Km long open wire line terminated in its characteristic impedance  and having the following parameters.   L=0.004H, .  Calculate the characteristic impedance, propagation constant and the phase velocity.                                                                  (8)

Q.9     a.   Design a constant K band pass filter section having cutoff frequencies of   2 KHz and 5 KHz and a nominal impedance of .  Draw the configuration of the filter.                                                  (8)

b.   Derive the design equations of an asymmetrical lattice attenuator to have a characteristic impedance of  and attenuation of N in nepers.             (8)