RF Modelling and Antennas - Dec 2011

Electronics & Telecomm. (Semester 5)

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.

Write short notes on following :-

1 (a) Chip components(5 marks) 1 (b) Microstrip lines and strip lines(5 marks) 1 (c) Large signal FET model(5 marks) 1 (d) ABCD Parameters(5 marks) 2 (a) Explain what is Skin depth? Calculate the skin depth for copper and aluminium at 0.86 and 1.2 GHz? Also find the resistance of an 8 cm wire with diameter of 1.5 mm? $$ \sigma_{CU}=64.516 \times 10^6 (s/m), \ \sigma_{Al}=40\times 10^6 (s/m) $$(10 marks) 2 (b) Explain with the equivalent circuits the Radio frequency behavior of Resistor, Inductor and Capacitor?(10 marks) 3 (a) Explain the folllowing terms related to the filter Design? Insertion Loss, Ripple Factor, Bandwidth(6 marks) 3 (b) Explain why the ideal filter response cannot be realized?(4 marks) 3 (c) Design the Butterworth High pass filter having cutoff frequency of 250 MHz and -15dB response at 200 MHz?(10 marks) 4 (a) Plot the following Impedance points on the smith chart? Z₀=50Ω
23+j 42Ω, 12-j 109Ω, 72+j 42.5Ω and 115-j 22Ω
Calculate their equivalent admittance using smith chart?(8 marks) 4 (b) Calculate the input impedance of the Transmission line using equations and the smith Chart, for Z₀=50Ω, Z₁=110+j 22Ω, ε_r=1.0, length of the line = 20 cm and operating frequency equal to 1.8 GHz?(12 marks) 5 (a) Explain the equivalent circuit of the transmission line?(5 marks) 5 (b) Derive the input impedance equation of Transmission line of length 'I'>(5 marks) 5 (c) Using the input impedance equation of Transmission line, derive the input impedance equation for shorted and open circuit transmission line and draw their voltage, current and impedance waveform?(10 marks) 6 (a) Define and derive AC parameter for BJT and FETs?(10 marks) 6 (b) Write short notes on,
(i) High Electron Mobility Transistor
(ii) Small signal BJT model?(10 marks) 7 (a) How the capacitor and inductors are realized using the sections of transmission line? Explain the same using the smith charts ?(6 marks) 7 (b) What are Kuroda Identities? How they are used in realization of RF filters?(10 marks) 7 (c) Explain what are Schottky Contacts?(4 marks)