Rashtrasant Tukadoji Maharaj Nagpur University 2011 B.E Electronics & Communication Engineering Faculty of Engineering and Technology, FIELDS AND RADIATING SYSTEM - Question Paper

part A
1. (a) Derive the field component of parallel plane waveguide using Maxwells equations in the free space ranging from perfectly conducting planes.
(b) Show that the waveguide for TE and TM waves in parallel plane waveguide behaves like a High Pass Filter. Determine the waveguide for TEM wave.

2. (b) Derive the expression for attenuation factor of parallel plane waveguide for TEM wave.
(b) A parallel plane waveguide is formed using 2 parallel sheets of copper spaced 4cm apart in free space, the conductivity and permeability of copper wire being provided by s= 5.8*107 O/m and µr=µ0=4p*10-7 H/m respectively. If the frequency of the wave is 10GHz, obtain the attenuation coefficient due to conductor losses due for
(i) TE10 mode
(ii) TEM mode

3. (a) Show that if a rectangular waveguide of dimensions a and b is filled with a dielectric material of e=e0er, the guide wavelength corresponding to TE10 mode is provided by:
?g= ?0/v(er-(?0/2a)^2 ) where ?0 is the free space wavelength.
(b) Derive the field components for TM wave in Rectangular waveguide.

4. (a) Prove that input impedance of an infinite transmission line is equal to its characteristics impedance. Also, determine the input impedances for the subsequent conditions:
(i) For Lossless Transmission line.
(ii) For Short circuited Transmission line
(iii) For Open circuited Transmission line
(b) Derive and discuss the expression for Reflection coefficient, extended of length l along the (+ve) x-direction of propagation.

5. (a) describe the terms characteristics Impedance and propagation constant for a Transmission line. compute characteristics impedance and propagation constant for a line having R= 0.2Om, L= 15mH/m, G=2O/m and C=15µF/m.
(b) The characteristics impedance of a transmission line is 50O and VSWR is two when the line is loaded. The minima shift 0.16? towards the load, when the load is shorted. Determine the load Impedance using Smith Chart.

part B

6. (a) Derive the expression for near and far fields for alternating current element situated at origin in spherical coordinate system.
(b) Show that effective area is the ratio of power available at the antenna terminals to the power per unit area of the incident wave.

7. (a) A short current element of length ?/20 carries a current of 10A at a frequency of 10MHz. compute the electric field intensity at a distance of 2Km from the current element. compute the Radiation Resistance of the above current element.
(b) State and prove the Reciprocity theorem applied to antenna.

8. (a) Prove that power gain of lossless antenna using a paraboloid reflector is provided by:
AP=6?(D/?)?^2, where D is the diameter of the paraboloid.
(b) compute the Directivity of an antenna which radiates uniformly is all directions.

9. (a) What is broadside and endfire arrays? Derive the expression for the array factor of linear broadside array of n-elements.
(b) compute the directivity and HPWB of major lobe for an end fire array of 2 vertically oriented half wave dipoles spaced half wavelength apart to form an array.

10. Write short notes on (any THREE):
(i) Travelling wave antenna
(ii) trend Antenna
(iii) Horn antenna
(iv) Yagi antenna
(v) Dish antenna

Earning:   Approval pending.