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Posted By: neyha Member Level: Gold Posted Date: 08 May 2008
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2006 Anna University Electronics and Communication B.E./B.TECH.DEGREE EXAMINATION :MICROWAVE ENGINEERING Question paper
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B.E./B.TECH.DEGREE EXAMINATION MAY/JUNE 2006
VII -SEMESTER
MICROWAVE ENGINEERING
TIME :3 hrs
MAX MARKS :100
PART -A (10 X 2 = 20 MARKS)
1. Write down the transmissio parameters of an ideal transformer of turns ratio n:1
2. Express S11 of two port microwave component in terms of its equivalent ABCD parameters
3. For reciprocal two port microwave component the magnitude of scattering coefficient S11 is 0.091. Find its VSWR.
4. Obtain the coupling coefficient in dB of a directional coupler if the magnitude of its corresponding scattering parameter is 0.707.
5. What is C ring tuning with respect to Magnetron?
6. Write down two important difference between TWT and multi cavity klysron
7.Name two important materials that are used in Schottky -barrier diode.
8. Mention two basic difference between IMPATT and BARITT in terms of biasing and NOISE
9. Write down the bsic difference between 'Barretters' and 'Thermistors'.
10. Write down the relationship of uide wavelength ,cut off wavelength and free space wavelength of a waveguide.
PART -B (5 X 16 = 80)
11.(i) Name three different types of devices that are used to detect microwave piwer.
(ii) What is the specific application of 'Double minma method' of microwave measurement?
(iii) How do you measure the micowave frequency without frequncy meter?
12 (b) (i) Obtain the ABCD parameters of a series impedance Z ohms from the first priciple.
(ii) An ideal transformer has 1000 turns on its primary and 100 turns on its secondry side. Assuming that it has a 50 ohms connectot on each side ,determine its scaterring parameters.
13 (a) (i) Is it possible to match all the oorts of alossless reciprocal microwave component ? Prove the same.
(ii) The specification of a three port circulator are given as isolation = 30 dB , insertion loss = 2 , 5 dB and VSWR = 1.2. charecterize the circulator by its S- parameters.
OR
(b) (i) One wishes to realize a power divider with a power ratio of 2.5:1 between the two outputs. Determine the charecteristics impedence of the two output lines , with a 50 ohm input and evaluute all the terms of the scattering matrix
(ii) Determine the scatering matrix of a crossing between two lines having charecteristic impedence of 50 ohms and 100 ohms
14 (a) (i) Draw any four types of SLOW WAVE STRUCTES used in TWT.
(ii) Draw the electrical equivalent diagram of a cavity type magnetron
(iii) What is ' strapping' with respect to magnetron?
(iv) What are 'pushing' and 'pulling' with respect to magnetron?
OR
(b) A two cavity klystron operates at 4.5 GHz . The DC beam voltage is 10 KV, cavity gap spacing is 2 mm . For a given input, the magnitude of the gap voltage is 100 volts , the DC component Io = 3.6 A and the drift regeion l= 3 cm . Calculate (i) the item the electrons are in the gap 9ii0 the transit angle (iii )the range of velocities of eletrons as they leave the gap reageion (iv) the maximum voltage gain.
15 (a) (i) Draw the equivalent circuit of schottky diode and write down its properties
(ii) Draw the equivalent circuit of pin diode and show how it can be used as a TRANSMISSION TYPE SWITCHED LINE PHASE SHIFTER and as a SERIES SWITCH
OR
(b) (i) Pictorially represent the charecteristics (viz eletric field distribution ,the microwave voltage and the external current flow) of differnt regeions of the IMPATT diode under reverse biased condition . Write down its typical charecteristics.
(ii) Give the voltage current wavefrom with respect to time of a TRAPATT diode and write down its charecteristics
(iii) Write down the advantages and limitations of PARAMETRIC AMPLIFIER
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