# GTU previous question paper BE VII Sem Microwave Engineering June 2012

## Subject Name: Microwave Engineering

Instructions:

1. Attempt all questions.

2. Make suitable assumptions wherever necessary.

3. Figures to the right indicate full marks.

Q.1 (a) What are microwaves? Explain advantages of microwave and its applications.

(b) Derive necessary equations for attenuation constant and phase constant with

reference to EM wave propagating along transmission line.

Q.2 (a) Sketch circular and rectangular waveguide and compare their dominant mode ,advantages and disadvantages.

(b) The dimension of a waveguide is 2.5X1cms.The frequency is 8.6GHz Find the possible modes that can propagate through the waveguide also find the cutoff frequencies for the same.

OR

(b) A rectangular waveguide is filled by dielectric material of _r =9, with inside dimension of 7X3.5cm. It operates in the dominant TE10 mode. Determine (i) cut off frequency (ii) phase velocity at a frequency of 2 GHz (iii) guided wavelength at the same frequency.

Q.3 (a) Draw and explain waveguide band, corners and twist in detail with their

applications.

(b) What is the purpose of directional Coupler. Define coupling factor, directivity, isolation of Directional coupler and write expression for each.

OR

Q.3 (a) A typical transmission line has a resistance of 6_ /km, inductance of 2.2mH/km, a capacitance of 0.005 μF/km and a conductance of 0.05μmho/km. Calculate the characteristic impedance, attenuation constant and phase constant of the transmission line at a frequency of 1kHz.Alo calculate the phase velocity of the signal

(b) Explain the operation of Magic TEE with its s-parameter. Also list some applications of magic TEE

Q.4 (a) Explain the mechanism of oscillations of Magnetron Oscillator with the aid of suitable diagram and discuss its performance characteristics.

(b) Explain the amplification process for a helix type travelling wave tube. What are its different applications?

OR

Q.4 (a) Describe the construction and working of a reflex klystron. Explain how velocity and current modulation takes place using the Applegate diagram.

(b) Explain the Tunnel diode characteristics with the aid of Energy band diagram.

Q.5 (a) Derive the radar range equation. Calculate the maximum range of a radar system which operates with a wavelength at 3 cm with a peak pulse power of 600KW if effective aperture of antenna Ae is 5 m2, minimum detectable signal is 10-13 W and the radar cross sectional area of the target is 20 m2.

(b) Explain Gunn effect using two valley theory.

OR

Q.5 (a) What is a pulsed radar? Explain the pulsed radar with its block diagram.

(b) Explain IMPATT Diode with its construction, working and application.