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B.Tech EC Microwave Exam 2020-21

This document is the end semester examination for a 7th semester B.Tech in Electronics and Communication Engineering course on Microwave Devices and Circuits. It contains 5 questions testing knowledge of scattering parameters, directional couplers, image parameter method, filter design, waveguides, and circulator operation. Students are asked to solve problems related to analyzing microwave networks, designing low-pass and high-pass filters to certain specifications, finding waveguide cutoff frequencies, and determining the S-matrix of a given circulator.

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43 views2 pages

B.Tech EC Microwave Exam 2020-21

This document is the end semester examination for a 7th semester B.Tech in Electronics and Communication Engineering course on Microwave Devices and Circuits. It contains 5 questions testing knowledge of scattering parameters, directional couplers, image parameter method, filter design, waveguides, and circulator operation. Students are asked to solve problems related to analyzing microwave networks, designing low-pass and high-pass filters to certain specifications, finding waveguide cutoff frequencies, and determining the S-matrix of a given circulator.

Uploaded by

jdn6qkm3l1
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERING

NATIONAL INSTITUTE OF TECHNOLOGY ROURKELA-769008


END SEMESTER EXAMINATION (Autumn) 2020-21

CLASS: B.Tech. EC (7th Semester) Max. Marks: 50

SUBJECT: Microwave Devices and Circuits (EC-6401) Time: 2 Hours

Q.nos Answer ALL questions. Marks


All parts of a question should be answered in one place.
Figures in the right-hand margin indicate marks.
1.(a) Consider two two-port networks with individual scattering matrices, [SA] and [SB].
Show that the overall S21 parameter of the cascade of these networks is given by 3
S21A S21B
S21 =
1-S22A S11B
A symmetric directional coupler with infinite directivity and a forward
(b) attenuation of 20 dB is used to monitor the power delivered to a load Zl.
Bolometer 1 introduces a VSWR of 2.0 on arm 4; bolometer 2 is matched to arm 7
3. If bolometer 1 reads 8 mW and bolometer 2 reads 2 mW, find: (a) the amount
of power dissipated in the load Zl; (b) the VSWR on arm 2.

2(a) Compute the image impedance and propagation factor for the network shown
below. 2

1
Design a composite low-pass filter by the image parameter method with the
(b) following specifications: R0 = 50  , fc= 50 MHz, and f∞=52 MHz. Plot the 8
insertion loss versus frequency curve.

Discuss the operation of a Wilkinson Power Divider with a neat sketch. Show
3.(a) 6
the even and odd mode analysis with the help of ABCD parameters.

(b) In a quarter wave transformer, show that the overall or total reflection coefficient 4
of a wave is given by

4.(a) Design a low-pass maximally flat filter having a passband of 0 to 3 GHz, and an
attenuation of 20 dB at 5 GHz. The characteristic impedance is 75 Ω.
Plot the insertion loss versus frequency curve. 5
[Choose N=5, g1=0.618, g2=1.618, g3=2.0, g4=1.618, g5=0.618]

(b) Design a five-section high-pass filter with a 3 dB equal ripple response, a cutoff
frequency of 1 GHz, and an impedance of 50 Ω. What is the resulting 5
attenuation at 0.6 GHz? Plot the insertion loss versus frequency curve.
[Choose N=5, g1=3.4817, g2=0.7618, g3=4.538, g4=0.7618, g5=3.4817]

Find the cutoff frequencies of the first four propagating modes of an air-filled
5.(a) copper X-band waveguide with dimensions a = 2.28cm, b = 1.01cm whose 5
operating frequency f =10GHz.

A three-port circulator has an insertion loss of 1 dB, isolation 30 dB and VSWR


(b) 5
= 1.5. Find the S-matrix.
All the Best !

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