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

**GUJARAT TECHNOLOGICAL UNIVERSITY**

**BE- VII****th ****SEMESTER–EXAMINATION – MAY/JUNE- 2012**

**Subject code: 171001 **

**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. ** **

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