Annauniversity Question Papers

B.E./B.TECH.DEGREE EXAMINATION ,APRIL/MAY 2005 VII -SEMESTER MICROWAVE ENGINEERING TIME :3 hrs MAX MARKS :100 PART -A (10 X 2 = 20 MARKS) 1.Writw down the scattering matrix of an ideal lossless transmission line of length 'l' units. 2. Write down the transmission parameters of an ideal lossless transmission line of length 'l' units. 3. Find the magnitude of scattering parameters of a reciprocal two port microwave component having the VSWR as 1.4 and the insertion loss dB. 4. A wave guide load is used to absorb 2 W of average power .The reflected power is 3mW .Find the magnitudeof VSWR 5. State any two difference between TWT and klystron amplifier. 6. Draw the electrical equivalent of cavity type magnetron 7. Give any two difference between microwave transistors and transferred electron devices. 8. Draw the equivalent circuit in a pin code under reverse bias 9. Compare a barretter with a thermistor 10 What are the minimum and maximum values of VSWR? Give the corresponding values of reflection coefficients. PART - B 11. State and prove the properties of scattering matrix 12 (a) (i) In a two hole directional coupler ,prove that the power coming out in the couplrd port is finite and that in the fourth is zerro (ii) Find the attunation in decibels for an ideal rotary vane attenuator foe vane rotation of 0 degrees and 60 degrees (iii) Deduce the formula used in the above subdividsion (ii) OR (b) Find the scattering matrix of an ideal , symmetrical,lossless,magic T junction 13 (a) (i) Draw schematic diagram of a two cavity Klystron amplifier. (ii) Find the first principle derive the expression for the power output and efficiency of the two cavity klystron amplifier

OR (b) (i) Draw four types of SLOW WAVE structures used in TWT. (ii) For a travelling wave tube Io = 300 mA,Vo = 5 kV, and the impedence of the helixs is 30 ohms. Find the length l of the helix that will give a gain of 60 dB at 9 GHz 14 (a) (i) Using Ridley - Watkins - Hilsum theory, explain two valley model of GaAs (ii) Hence or otherwise show how negative resistance charecteristics is obtained in Gunn diode. OR (b) Show how apin code is used as (i) Switch (ii) AN attenuator (ii) a phase shifter 15 (a) (i) What are the three quantities to be measured to determine the impedence of a load at mocrowave frequencies (ii) Draw the experimental set up to find the frequency of a microwave generator (without using the frequenc meter ) and mention the procedure OR (b) (i) Prove the relationship among guide wavelegth cutoff wave length and free space wavelength of a rectangular waveguide (ii) Draw the experimental set up to find the high VSWR and mention the procedure