RF Modelling and Antennas - December 2015

MU Electronics and Telecom Engineering (Semester 5)

Total marks: --
Total time: -- INSTRUCTIONS
(1) Assume appropriate data and state your reasons
(2) Marks are given to the right of every question
(3) Draw neat diagrams wherever necessary 1 (a) Explain hazard of electromagnetic radiation. 5 marks

1 (b) Find the attenuation of a 4 element 2.5 db ripple low pass Chebyshev filter at ω/omega_c=2.5. 5 marks

1 (c) What are isotropic pattern and Omnidirectional pattern. Give one example for each. 5 marks

1 (d) Explain near and far field radiation related to antenna. 5 marks

2 (a) Discuss design procedure for filter using image parameter method. 5 marks

2 (b) Design a LPF whose input and output ports are matched to 50Ω impedance with cutoff frequency of 3 GHz, equi-ripple of 0.5 dB and rejection of at least 40 dB at approx. twice the cutoff frequency. 5 marks

3 (a) Explain significance of retarded magnetic vector potential and retarded electric scalar potential. 5 marks

3 (b) Derive radiation resistance of half wave dipole antenna and monopole antenna. 5 marks

4 (a) Find the radiation pattern for an array of 4 elements fed with same amplitude and same phase. Find its HPBW and BWFN. 5 marks

4 (b) State and prove Reciprocity theorem as applicable to antennas. 5 marks

5 (a) Design Dolph-T Chebyshev array of 6 elements with spacing 'd' between elements with a major to minor lobe ratio of 26 dB. Calculate the excitation coefficients. 5 marks

5 (b) Explain the structure of Microstrip antenna. Discuss its feed mechanisms and applicatins. 5 marks

6 (a) Log periodic antennas. 5 marks

6 (b) Schottky diode. 5 marks

6 (c) Broad side and End fire array. 5 marks

6 (d) Feeding methods of Parabolic antenna. 5 marks