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    21et54-Rf Circuits MQP

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    VIJETHA J

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    21et54-Rf Circuits MQP

    Uploaded by

    VIJETHA J
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    21et54-Rf Circuits Mqp

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    4 views3 pages

    21et54-Rf Circuits MQP

    Uploaded by

    VIJETHA J

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    of 3

    COURSE CODE: 21ET54

    USN
    RV COLLEGE OF ENGINEERING
    Autonomous Institution affiliated to VTU
    V Semester B.E. April -2024 Examinations
    DEPARTMENT OF ELECTRONICS AND TELECOMMUNICATION ENGINEERING.
    RF Circuits
    (2021 SCHEME)
    Time: 03 Hours Maximum Marks: 100
    Instructions to candidates:
    1. Answer all questions from Part A. Part A questions should be answered in first three pages of the answer
    book only.
    2. Answer FIVE full questions from Part B. In Part B question number 2 is compulsory. Answer any one full
    question from 3 and 4, 5 and 6, 7 and 8, and 9 and 10.
    PART-A (Objective type for one or two marks)
    (True & false and match the following questions are not permitted)
    1 1.1
    Define VSWR. Write down the expression for VSWR in terms of reflection 2
    coefficient.
    1.2
    What is the condition to check the lossless property of any N port network in terms of 2
    S Parameters.
    1.3
    Draw figure to show construction of PIN diode and its equivalent circuit 2
    configuration in forward and reverse bias condition.
    1.4 List the important factors in the selection of matching network 2
    1.5 A waveguide termination having VSWR of 1.1 is used to dissipate 100 watts of 2
    power. Find the reflected power.
    1.6 A matched isolator has insertion loss of 0.5dB and isolation 25dB. Find the scattering 2
    coefficients.
    1.7 Write the S-Matrix of the branch line coupler 1
    1.8 Why semiconductor phase shifters are preferred compared to ferrite phase shifters 1
    1.9 Write the frequency transformation of normalized low pass to band pass filter. 2
    1.10
    Define velocity modulation process in Reflex Klystron oscillator 2

    1.11
    Define MMIC. How does it differ from a hybrid IC? Write any two. 2

    PART-B (Maximum subdivisions is limited to 4 in each question)


    UNIT-I
    2 a Write the lumped equivalent circuit for the transmission line. Derive the expression for 8
    the current and voltage in a transmission line
    Design a microstrip line on a 0.5 mm alumina substrate (εr = 9.9, tanδ=0.001) for a
    b 50Ω characteristic impedance. Calculate the length of this line required to produce a 8
    phase delay of 270o at 10 GHz, and compute the total loss on this line, assuming
    copper conductors.

    UNIT-II
    A load impedance of 40 + j70Ω terminates a 100Ω transmission line that is 0.3λ
    3 a long. Using a smith chart, calculate the reflection coefficient at the load, the 8
    reflection coefficient at the input to the line, the input impedance, the standing
    wave ratio on the line, and the return loss.
    b Discuss the construction of resistance and reactance circle in smith chart 8
    OR

    A 300 Ω line is terminated by an unknown impedance. VSWR is 4.48 and the first
    4 a voltage minimum is situated at 6cm from the termination when the frequency is 8
    200MHz. Using a smith chart, determine the unknown load impedance if the line is
    air.

    b Design a matching network using a single shunt open stub as a tuning element to 8
    match a load impedance ZL=15+j10 Ω to a 50 Ω transmission line

    UNIT-III
    Explain the following waveguide components with diagram
    i) E-plane Tee
    5 a ii) H-plane Tee 8
    iii) Microwave attenuator
    iv) Matched Terminations

    A 20mW signal is fed into one of collinear port 1 of a lossless H-plane T-junction.
    b Calculate the power delivered through each port when other ports are terminated in 8
    matched load
    OR

    6 a Explain the design of equal and unequal wilkinson power divider and branch line 8
    coupler

    Design a maximally flat low-pass filter with a cutoff frequency of 2 GHz,


    b impedance of 50 Ω , and at least 15 dB insertion loss at 3 GHz. 8
    (Assume N=5, Filter coefficients are: g1=0.618, g2 = 1.618, g3 = 2.000, g4 =
    1.618, g5 = 0.618)

    UNIT-IV
    7 a Explain with neat diagram, how reflex klystron generates microwave oscillations 8

    b Explain the V-I characteristics of a GUNN diode and the modes of operation of the 8
    diode.

    OR

    8 a Explain the construction and operation of GaAs MESFET. Draw its small signal 8
    equivalent circuit in common source configuration.
    Illustrate the working of transmission type switched line phase shifters and
    b reflection type hybrid phase shifters. 8
    UNIT-V
    Explain the following two port power gains with necessary equations
    9 a i) Power Gain 8
    ii) Available Power Gain
    iii) Transducer Power Gain
    A silicon bipolar junction transistor has the following scattering parameters at 1.0
    GHz, with a 50 Ω reference impedance

    b 8

    The source impedance is ZS = 25Ω and the load impedance is ZL = 40Ω . Compute
    the power gain, the available power gain, and the transducer power gain.
    OR
    10 a Discuss the conditions for stability of the transistor amplifier. 8
    The GaN HEMT has the following scattering parameters at 1.9GHz (Zo=50 Ω)

    b 8

    Determine the stability of this transistor by using K- Δ Test and the μ - Test.

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