Rr320404-microwave-engineering

Set No. 1

Code No: RR320404

III B.Tech II Semester Supplimentary Examinations, Aug/Sep 2008 MICROWAVE ENGINEERING (Electronics & Communication Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. (a) What are the applications of microwave frequencies? Discuss in detail. (b) Explain the principle of operation of a reflex Klystron oscillator and derive an expression for the bunching parameter. [6+10] 2. (a) What are the desirable properties of slow wave structures to be used in TWT amplifiers. (b) Draw a neat sketch of traveling wave tube and explain its principle of operation with bunching diagrams. [8+8] 3. (a) Draw the sketches of different types of magnetron anodes. (b) Explain Hatree conditions. Derive the voltage under this condition for linear magnetron. [6+10] 4. (a) Describe a non-degenerate negative resistance parametric amplifier. (b) An N type Ga As GUNN diode has the following specification Threshold field: 3KV/m Applied field 3.5KV/m Device length 10 micrometers Doping Constant 1014 electron/ Cm3 Operating freq. 10 GHz Calculate the current density and (-Ve) electron mobility in the device, explaining the relations used. [6+10] 5. (a) Derive the expression for the attenuation of T E10 mode of a rectangular waveguide with finite conductivity. (b) An air filled rectangular cavity with brass walls has σ = 1.54 × 107 (s/m) and the following dimensions a= 4 cm, b = 3 cm and d = 5 cm. Determine: i. The dominant mode and its resonant frequency for this cavity. ii. Find the Q and the time average stored electric and magnetic energies at resonant frequency, assuming H0 to be 0.1 A/m. [8+8] 6. (a) Sketch a 4 port Hybrid junction. Justify that it is basically a 3 dB directional coupler. (b) A 20-mw signal is fed into the series arm of a loss less Magic Tee junction. Calculate the power delivered through each port when other ports are terminated in matched load. [8+8] 1 of 2

Set No. 1

Code No: RR320404

7. (a) What are ferrites? What property do they have different from ordinary conductors or insulators? (b) Describe any one microwave component which make use of Faraday rotation principle, with neat sketches. [8+8] 8. (a) What are the precautions to be taken while setting up microwave bench for measurement of various parameters. (b) How do you measure microwave power using a Bolometer. ⋆⋆⋆⋆⋆

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[8+8]

Set No. 2

Code No: RR320404

III B.Tech II Semester Supplimentary Examinations, Aug/Sep 2008 MICROWAVE ENGINEERING (Electronics & Communication Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. (a) Discuss the limitations of conventional tubes at microwave frequencies. (b) Explain the principle of operation of two cavity Klystron with neat diagrams. [6+10] 2. (a) A helix traveling wave tube is operated with a beam current of 300 mA, beam voltages of 5 KV and characteristic impedance of 20 Ohm. What length of the helix will be selected to give a output power gain of 50 dB at 10 GHz. (b) Explain how the amplification takes place in TWT. Compare its bandwidth with Klystron amplifier.. [10+6] 3. (a) Derive an expression for the Hull cut off condition for cylindrical magnetron oscillator. (b) Write short notes on “8 cavity magnetron”

[8+8]

4. (a) Describe a non-degenerate negative resistance parametric amplifier. (b) An N type Ga As GUNN diode has the following specification Threshold field: 3KV/m Applied field 3.5KV/m Device length 10 micrometers Doping Constant 1014 electron/ Cm3 Operating freq. 10 GHz Calculate the current density and (-Ve) electron mobility in the device, explaining the relations used. [6+10] 5. (a) Find the dimensions of rectangular waveguide to be used to propagate the frequency of 8 GHz to 12 GHz for dominant mode operation. (b) Derive an expression for Q of a cubic cavity supporting T E101 mode.

[8+8]

6. (a) State the properties of E plane Tee and H plane Tee. (b) Show that a symmetrical magic Tee is a 3dB directional coupler.

[8+8]

7. (a) Enumerate the properties of S parameters. (b) Formulate the S parameter matrix of a 4 port circulator.

[8+8]

8. (a) Explain VSWR measurement procedure in microwave laboratory with a suitable microwave bench setup. (b) Calculate VSWR of a rectangular guide of 2.3cm x 1.0 cm operating at 8 GHz. The distance between twice minimum power points is 0.09 cm. [8+8] 1 of 2

Set No. 2

Code No: RR320404 ⋆⋆⋆⋆⋆

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Set No. 3

Code No: RR320404

III B.Tech II Semester Supplimentary Examinations, Aug/Sep 2008 MICROWAVE ENGINEERING (Electronics & Communication Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. (a) Explain clearly the different high frequency effects in electron tubes and show how these are eliminated in the design of a high frequency microwave tube. (b) The bunching grids of a Klystron amplifier are 2 mm apart. The beam voltage is 2KV and the drift space is 2.8 cm. Long. What must be the value of the RF voltage at the bunching grid to produce maximum fundamental components of the current at the catcher. Assume the operating frequency 2.8 GHz. On what factors does the bunching parameter depend upon. [8+8] 2. (a) Explain the use of slow wave structure in TWT amplifier. Give neat sketches of different structures. (b) Explain the working of a O-type Backward wave oscillator.

[8+8]

3. (a) Explain the principle of Π mode oscillations in cylindrical magnetron. (b) Write short notes on ‘Reike’ diagram and its significance.

[8+8]

4. (a) Write short notes on “Parametric up converter”. (b) What is a MASER? What does its name signify? What applications does it have? [8+8] 5. (a) A rectangular wave-guide has a cross section of 1.5 cm x 0.8 cm, σ=0, µ= µ0 and ∈= 4∈0 . The is given as
magnetic
field component 3πy 11 Hx = 2Sin πx cos Sin (π × 10 t − β z) A/m a b Determine: i. ii. iii. iv. v.

The The The The The

mode of operation cut off frequency phase constant propagation constant wave impedance.

(b) Write short notes on “Rectangular resonant Cavity”.

[10+6]

6. (a) Explain the working of two hole directional coupler with a neat diagram. (b) Explain about E plane Tee junction with a neat sketch. Why it is called a series Tee? [8+8] 7. (a) What are ferrites? List out their characteristics. (b) What are scattering parameters? Explain the S matrix of a three port ideal circulator. [8+8] 1 of 2

Set No. 3

Code No: RR320404

8. (a) Explain how you measure VSWR of given load for all kinds of loads possible. (b) Give the measurement procedure of Q factor of a resonant cavity. ⋆⋆⋆⋆⋆

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[8+8]

Set No. 4

Code No: RR320404

III B.Tech II Semester Supplimentary Examinations, Aug/Sep 2008 MICROWAVE ENGINEERING (Electronics & Communication Engineering) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks ⋆⋆⋆⋆⋆ 1. (a) What is velocity modulation? Explain how amplification takes place in a two cavity Klystron amplifier. (b) What is transit time? How it is made use of in realization of microwave tubes. [10+6] 2. (a) What is a backward wave oscillator? Write brief notes on its configuration and characteristics. (b) Describe the merits and demerits of helix as a slow wave structure.

[8+8]

3. (a) What are disadvantages of strapping? Show the cross section of a magnetron anode cavity system that does not require stapping. (b) What is critical magnetic field as it is used in connection with magnetron? Derive an expression for cut off magnetic field in linear magnetron. [8+8] 4. (a) Describe a non-degenerate negative resistance parametric amplifier. (b) An N type Ga As GUNN diode has the following specification Threshold field: 3KV/m Applied field 3.5KV/m Device length 10 micrometers Doping Constant 1014 electron/ Cm3 Operating freq. 10 GHz Calculate the current density and (-Ve) electron mobility in the device, explaining the relations used. [6+10] 5. (a) A rectangular wave-guide has a cross section of 1.5 cm x 0.8 cm, σ=0, µ= µ0 and ∈= 4∈0 . The is given as
magnetic
field component 3πy πx 11 Hx = 2Sin a cos b Sin (π × 10 t − β z) A/m Determine: i. ii. iii. iv. v.

The The The The The

mode of operation cut off frequency phase constant propagation constant wave impedance.

(b) Write short notes on “Rectangular resonant Cavity”.

[10+6]

6. (a) Explain the working of two hole directional coupler with a neat diagram. 1 of 2

Set No. 4

Code No: RR320404

(b) Explain about E plane Tee junction with a neat sketch. Why it is called a series Tee? [8+8] 7. Write short notes on: (a) Properties of S matrix. (b) Gyrator and its applications.

[8+8]

8. Explain with a neat black diagram how VSWR and impedance can be measured using a slotted line in X band. Name the types of sources used and list out the precautions to be taken. [16] ⋆⋆⋆⋆⋆

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