Circuits and Transmission Lines - May 2015

Electronics & Telecomm. (Semester 3)

TOTAL MARKS: 80
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any three from the remaining questions.
(3) Assume data if required.
(4) Figures to the right indicate full marks.

1 (a) Determine y-parameter for the network. (5 marks)

1 (b) The constants of a transmission line are R=6Ω/km, L=2.2 mH/Km.G=0.25×10^-6 ℧/km, C=0.005×10^-6 F/km.
Determine the characteristics impedance, propagation constant and attenuation constant at 1 KHZ. (5 marks)

1 (c) Test if F(S)=2S⁶+4S⁵+6S⁴+8S³+6S²+4S+2 is a Hurwitz polynomial. (5 marks)

1 (d) The current I(S) in network is given by $$ I(S) = \dfrac {2(S)} {(S+1)(S+2)}. $$ Plot the pole-zero pattern in the S-plane and hence obtain i(t). (5 marks)

2 (a) Find the current through 10Ω resistor using Norton's theorem. (10 marks)

2 (b) Find the current i(t) for t>0. (10 marks)

3 (a) Find Foster I and Foster II forms of the driving points function: $$ F(S) = \dfrac {S^3 + 9S^2 + 23S + 15 } {S(S^3+ 12S^2 + 44S + 48)} $$ (10 marks)

3 (b) Determine ABCD parameters of the network shown: (10 marks) 4 (a) A transmission line has a characteristics impedance of 150 Ω and terminated in a load Z_L=75 - J100&Omega. Using switch chart, find
i) VSWR
ii) Reflection coefficient
iii) Input impedance at a distance 0.1λ from the load.
iv) location of first voltage maximum and first voltage minimum from the load.(10 marks)

4 (b) Find I₂ using mesh analysis. (10 marks)

5 (a) For the network shown, capacitor C has an initial voltage V_C(-0) of 10V and at the same instant current in the inductor L is zero. The switch is closed at time t=0. Obtain the expression for voltage V(t) across the inductor L. (10 marks)

5 (b) For the network shown, determine $$ \dfrac {V1} {I_1} \ and \ \dfrac {V_2} {I_1} $$ . Plot the poles and zeros. (10 marks)

6 (a) For the network shown, find the equivalent T-network. (10 marks)

6 (b) Derive condition for reciprocity in terms of Z parameters and symmetry in terms of h parameters. (10 marks)