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    You are on page 1of 6

    Seat No.: ________ Enrolment No.

    ___________

    GUJARAT TECHNOLOGICAL UNIVERSITY


    BE - SEMESTER–VI (NEW) EXAMINATION – SUMMER 2022
    Subject Code:3161003 Date:01/06/2022
    Subject Name:Antennas and Propagation
    Time:10:30 AM TO 01:00 PM Total Marks: 70
    Instructions:
    1. Attempt all questions.
    2. Make suitable assumptions wherever necessary.
    3. Figures to the right indicate full marks.
    4. Simple and non-programmable scientific calculators are allowed.
    MARKS
    Q.1 (a) Define the following terms: (i) Beam solid angle (ii) Directivity 03
    (iii)Antenna Aperture
    (b) Derive the expression of Friss transmission formula 04
    (c) Explain in the detail about Binomial array and pattern 07
    multiplication

    Q.2 (a) Explain the effect of ground on ungrounded antenna. 03


    (b) Discuss Dolph–Tchebysheff distribution for linear arrays. 04
    (c) Explain Non-metallic Dielectric lens and artificial dielectric lens 07
    antennas in detail.
    OR
    (c) Explain in detail about frequency scanning arrays. 07

    Q.3 (a) Calculate the percentage power reflected, if Antenna 03


    inputimpedance is (30+j40) and characteristic impedance of
    transmission line is 50.
    (b) Explain the features of Yagi Uda antenna. 04
    (c) State Babinet’s principle and illustrate its application to slot 07
    antennas and complementary antennas.
    OR
    Q.3 (a) Calculate the diameter of parabolic dish antenna, for given value 03
    of gain G = 40 dBand operating frequency 11 GHz.
    (b) Explain the working principle of small loop antenna. 04
    (c) Describe the properties of Endfire array. 07

    Q.4 (a) The maximum radiation intensity of a 90% efficiency antenna is 03


    200mW/ unit solid angle. Find the directivity and gain
    (dimensionless andin dB) when theInput power is 125.66 mW.
    (b) Along with necessary figure explain the principle of Folded dipole 04
    (c) Explain Cassegrain feed with required figure. 07
    OR
    Q.4 (a) Calculate the directivity of an antenna with circular aperture 03
    ofdiameter 3 meter at frequency 5 GHZ.
    (b) Explain about log periodic antenna with necessary figures. 04
    (c) Explain practical design consideration for the helical antenna. 07

    Q.5 (a) Describe various types of basic horns with figure. 03


    (b) Explain the Different modes of Radio wave propagation. 04

    Page 1 of 2
    (c) Obtain the ratio of Eθ and HФ field components of a current 07
    element at a distance point in free space with necessary derivations
    using Maxwell’s equation
    OR
    Q.5 (a) Explain multihop propagation briefly. 03
    (b) With figure describe the ionization layers. 04
    (c) With necessary figure and derivations explain N element array of 07
    equal amplitude and spacing. Write the equation for array Factor.

    *************

    Page 2 of 2
    Seat No.: ________ Enrolment No.___________

    GUJARAT TECHNOLOGICAL UNIVERSITY


    BE - SEMESTER–VI(NEW) EXAMINATION – WINTER 2022
    Subject Code:3161003 Date:13-12-2022
    Subject Name:Antennas and Propagation
    Time:02:30 PM TO 05:00 PM Total Marks:70
    Instructions:
    1. Attempt all questions.
    2. Make suitable assumptions wherever necessary.
    3. Figures to the right indicate full marks.
    4. Simple and non-programmable scientific calculators are allowed

    Q.1 (a) Enlist and define the different types of aperture of an antenna. 03
    (b) Derive the condition, When an antenna is act as radiator. Also discuss its 04
    different cases.
    (c) Write the statement of pattern multiplication theorem. Explain it in detail by 07
    using any example.

    Q.2 (a) Classify the antennas according to radiation pattern. 03


    (b) The measured Half Power Beam widths of an antenna in the two orthogonal 04
    planes are 30° and 20°. Antenna efficiency is 100%. Calculate the
    approximate gain of the antenna.
    (c) Draw and explain structure of Log periodic antenna. Derive its 07
    Mathematical equations for designing purpose.
    OR
    (c) Starting from retarded current, derive an expressions for electric and magnetic 07
    components of a short dipole antenna if the spherical system is defined in r, θ
    and ϕ

    Q.3 (a) What is meant by reciprocity Theorem? 03


    (b) Compare the far field equations of small loop with short dipole. 04
    (c) Describe the various forms of Horn antenna. Obtain the design equations of 07
    Horn antenna.
    OR
    Q.3 (a) Calculate the maximum effective aperture of a microwave antenna which has 03
    a directivity of 800. Frequency of operation is 6GHz.
    (b) Determine the distance from short dipole operating at 1MHz at which 04
    radiation filed is equal to the induction filed
    (c) Describe the procedure for the measurement of gain of antenna under test. 07

    Q.4 (a) Draw and explain the working principle of slot antenna. 03
    (b) What is the need for an antenna array? Distinguish: Broadside and End fire 04
    array
    (c) Discuss the principle of working of Parabolic reflectors. Explain the various 07
    feed techniques, their relative merits and demerits. Discuss the role of f/d ratio
    in the parabolic reflectors.(f-focal length, D- diameter of reflector)
    OR
    Q.4 (a) Enlist the different types of lens antenna and explain in brief. 03
    (b) Define the following terms: 04
    i) Pitch angle of helical antenna
    ii) Isotropic point source
    iii) Skip zone
    1
    iv) Critical frequency
    (c) Explain and design 4-element yagi-uda antenna 07

    Q.5 (a) Explain Super refraction briefly. 03


    (b) Discuss Dolph–Tchebysheff distribution for linear arrays. 04
    (c) Give the radiation mechanism of Microstrip antenna 07
    OR
    Q.5 (a) What is meant by virtual height in radio wave propagation? 03
    (b) Describe how helical antenna works in axial and normal mode. 04
    (c) Draw the structure of atmosphere and ionosphere and explain in detail the 07
    various regions of ionosphere.

    *************

    2
    Seat No.: ________ Enrolment No.___________

    GUJARAT TECHNOLOGICAL UNIVERSITY


    BE - SEMESTER– VI (NEW) EXAMINATION – WINTER 2021
    Subject Code:3161003 Date:24/11/2021
    Subject Name:Antennas and Propagation
    Time:10:30 AM TO 01:00 PM Total Marks: 70
    Instructions:
    1. Attempt all questions.
    2. Make suitable assumptions wherever necessary.
    3. Figures to the right indicate full marks.
    4. Simple and non-programmable scientific calculators are allowed.

    Q.1 (a) Define and discuss the Directivity of antenna under test with help of 03
    necessary formula.
    (b) Define the following terms: 04
    i) Radiation efficiency
    ii) HPBW
    iii) Beam area
    iv) Radiation pattern

    (c) Explain different types of antenna with necessary figures. 07

    Q.2 (a) "Antenna is a transitional structure". Justify 03


    (b) Discuss the different feeding methods with necessary figures. 04

    (c) Discuss the different types of antenna aperture with necessary figures 07
    and equations.
    OR
    (c) Derive the expression for the radiation resistance of half-wave dipole. 07

    Q.3 (a) Explain half power beam width with respect to antenna field and power 03
    pattern.
    (b) Sketch the helical geometry with its associated dimensions showing 04
    relationship between circumference, spacing, turn length and pitch angle
    of helix.
    (c) Explain Pattern Multiplication and show that it can be used to find the 07
    resultant pattern of a linear array. Specify the limitations of this method.
    OR
    Q.3 (a) Define axial ratio. What is the ideal value of it for circular polarization? 03
    (b) Discuss the antenna field zone with necessary figure. 04
    (c) Write the equation of Scalar potential and vector potential for short 07
    dipole and derive the equation of electric field components and magnetic
    field components from that.

    Q.4 (a) The radiation resistance of antenna is 70Ω and loss resistance is 10Ω. 03
    Calculate antenna efficiency.
    (b) Explain about ultra-wideband antenna. 04
    (c) Draw and explain structure of Log periodic antenna. Derive its 07
    mathematical equations for designing purpose.

    1
    OR
    Q.4 (a) Calculate the gain for parabolic antenna with circular aperture of 03
    diameter 6 meter at a frequency of 100 MHz.
    (b) List out the uses of loop antenna. 04
    (c) Explain (i) Binomial arrays. 07
    (ii) Schelkunoff theorems for linear arrays.

    Q.5 (a) Explain the features of Yagi Uda antenna. 03


    (b) Explain the different types of lens antenna? 04
    (c) Explain the operation of Microstrip patch antenna with neat diagram. 07
    OR
    Q.5 (a) Discuss significance of complementary antenna with the help of 03
    babinet’s principal.
    (b) Define the following terms.(draw necessary figures) 04
    (i) Duct propagation (ii) Skip zone
    (c) Enlist and explain the Different modes of Radio wave propagation. 07

    *************

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