Question Bank with Sol 2 PDF

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All Combined Notes and Question papers are attached in the file. The learner can go through any of the topics asked or want to read For Microwave Engineering subject....

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School of Electronics Engineering, KIIT University School of Electronics Engineering, KIIT-DU EC 3015 Microwave Engineering

5th Semester (ETC)

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Questions What are the frequency ranges of microwave L-band, X-band and Ku-band? Write one application for each of the above bands for microwave communication. What are the different microwave frequency bands between 1GHz and 30 GHz. What are the frequency ranges of UHF, VHF, Microwave and Millimeterwave? Write one example of communication for each of the above bands. Draw the field components for propagating Non-TEM mode, TEM mode, TE mode and TM mode, considering z-direction as the direction of propagation. Draw the diagram of a rectangular waveguide and write the boundary conditions applied to determine the field solutions inside the guide for TE and TM modes of propagation. What are the dominant TE and TM modes in a rectangular waveguide? Draw electric and magnetic field configurations for those dominant modes. Derive the field expressions for a rectangular waveguide for TM modes of propagation. What are cut-off wavelength and guided wavelength in a waveguide? Establish a relation between cut-off wavelength and guided wavelength in a waveguide. Prove that in a waveguide phase velocity (vp) and group velocity(vg) are related with velocity of light (c) by the expression vp x vg = c2. What is cut-off frequency in a waveguide? In a rectangular waveguide from the expression of phase constant (β), obtain the expression of cut-off frequency. A rectangular waveguide of dimensions 5 cm X 2 cm is used to propagate TM 11 mode at 10 GHz. Determine the cut-off wavelength and wave impedance. Starting from the electric and magnetic field expressions in a rectangular waveguide, determine wave impedances at TM mode and TE mode. A rectangular waveguide is filled with a dielectric having dielectric constant of 4. In a certain mode of propagation for z-directed wave Ez = 0 and Hx = 3Sin(πx/2b) Cos(3πy/b) Sin (π 1011t- βz) A/m. Identify the mode and calculate cut-off frequency of this mode, if b=7.5 mm. What are degenerate modes in a waveguide? An air-filled RWG has dimensions, a=5cm and b=4cm. Calculate two TM modes and

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two TE modes which can propagate through the guide at frequencies below 8 GHz. Derive the expression for phase velocity in a RWG. Draw the variation of phase velocity with frequency and explain the graph. Draw the diagram of a circular (cylindrical) waveguide (CWG). What are dominant TE mode and TM mode in a CWG? Draw electric and magnetic field configurations in a circular waveguide for dominant TE and TM modes. What is an electromagnetic resonator (cavity)? What are the dominant TE and TM modes in a rectangular cavity? Derive the field expressions for a rectangular waveguide for TE modes of propagation. Determine cut-off frequency, guided wavelength, phase velocity and group velocity for TE11 mode for 6 GHz signal, propagating through a RWG of dimension 4cmX3cm. A rectangular cavity has dimensions 6cm, 5cm and 4cm along x, y and z axes respectively. Calculate resonance frequencies for dominant TE and TM modes in the cavity. Write applications of waveguide and electromagnetic resonator. How quality factor of a rectangular cavity can be estimated? Determine cut-off wavelength, guided wavelength, phase velocity and group velocity for dominant TE10 mode for 2.5 GHz signal, propagating through a RWG of dimension 10cmX8cm. A rectangular cavity has dimensions 6cm, 5cm and 4cm along x, y and z axes respectively. Calculate resonance frequencies for dominant TE and TM modes in the cavity. What is an electromagnetic resonator (cavity)? What are the dominant TE and TM modes in a rectangular cavity? Explain in brief the high-frequency limitations of conventional vacuum tubes. What is the limitation of conventional vacuum tubes due to transit time effect? What is a re-entrant cavity? What is Backward Wave Oscillator (BWO)? What are mode jumping and strapping in a Magnetron? Why two-cavity Klystron oscillator is usually not constructed? Explain gain-bandwidth product limitation in conventional vacuum tubes. Explain the working principle of a 2-cavity Klystron amplifier. Obtain the expression for Beam-coupling coefficient for a 2-cavity Klystron amplifier. What is velocity modulation in a Klystron amplifier? Obtain the expression for bunching parameter in Klystron amplifier. Define gap transit time, gap transit angle, d. c. transit time, d. c. transit angle and depth of velocity modulation in a Klystron amplifier. A two cavity Klystron operates at 4 GHz with V 0 = 1 kV, I0 = 22 mA, cavity gap (L) of 1 mm and drift space (d) of 3 cm. Find out gap transit angle (θ g), beam coupling

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coefficient (βi) and d.c. transit angle (θ0). Explain velocity modulation in a Reflex Klystron? How condition of oscillation in a Reflex Klystron can be explained using electronic admittance spiral? What is a multi-cavity Klystron amplifier? A two-cavity Klystron amplifier with separation between buncher and catcher cavities of 4 cm is operating at 10GHz under d.c. anode voltage of 500V. If r.f. voltage inside the buncher cavity of gap spacing 2 mm is 2Sinωt Volt and beam coupling coefficient is 0.95, then calculate d.c. transit angle between the cavities and bunching parameter of the Klystron. Explain velocity modulation in a Reflex Klystron with the help of Applegate diagram? How condition of oscillation in a Reflex Klystron can be obtained using electronic admittance spiral? Explain velocity modulation in a Reflex Klystron with the help of Applegate diagram. Without derivation explain physically and using appropriate diagram that how oscillation in a Reflex Klystron can be explained using Electronic admittance spiral. Explain the principle of operation of a Magnetron Oscillator. Derive HULL cut-off magnetic field equation. What are mode jumping and strapping in a Magnetron? An eight cavity Magnetron oscillator of anode radius ‘a’ and cathode radius ‘b’ is operated at π-mode. Derive the expression for cyclotron frequency and find out the mode number of oscillation. What is π-mode in a Magnetron? Find out the mode number for a Magnetron operating at π-mode. What do you mean by ‘Strapping’ in a Magnetron Oscillator? A magnetron oscillator having cathode radius of 5 cm and vane edge to centre radius of 10 cm operates with anode voltage of 26 KV, beam current of 27 Amp and magnetic flux density of 0.336 Wb/m2. Calculate cyclotron angular frequency, cut-off voltage and cut-off magnetic flux density. What are slow wave structures? Explain the working principle of travelling wave tube (TWT). How a backward wave oscillator (BWO) operates? Why is it called ‘backward wave’? What is negative differential mobility in transferred electron devices (TEDs)? Explain current control mode and voltage controlled mode in a transferred electron device (TED). What is Gunn effect? Describe the two-valley model theory for n-type GaAs and derive the condition for negative resistance. What are the different modes of operation of Gunn diode? Describe with diagram the working principle of IMPATT Diode. Explain principle of operation of a PIN diode. Why ‘I’ region is used in a PIN diode? Explain the construction and principle of operation of Bolometer? Define S-parameters for a 2-port microwave network.

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Explain the principle of operation of E-plane Tee and H-plane Tee. Write down the scattering matrix of a Magic Tee with suitable diagram. What is a phase shifter? Explain the design principle of a waveguide directional coupler. A 2 Watt power source is connected with the input of a directional coupler with coupling factor 15 dB and Dirdctivity 35 dB. Find the output powers in dBm at the through, coupled and isolated ports. Assume all the ports are matched. What is a waveguide directional coupler ? Derive the S-matrix of the directional coupler. In a waveguide directional coupler, during measurement, it is found that power measured in VSWR meter at the input port is -30dB, at the output port is 32.5dB and at the coupled port is -40dB. Find out insertion loss and coupling factor. Describe the working principle of a variable attenuator. What is a crystal detector? What is a matched termination? Explain working principle of 3-port circulator. What are its applications? Find out S-matrix of a 3-port circulator. How a Rat race ring power divider works? Write down the scattering matrix of E-plane and H-plane Tees with suitable diagrams. What is Magic Tee? Write down S-matrix for a Magic Tee. What is Faraday rotation? Explain with necessary diagram the design principle of an Isolator. Find out the scattering matrix of a Rat race ring power divider? Describe the Memhod of measurement of antenna radiation pattern. What are the different methods of measuring microwave power? How unknown microwave frequency can be measured? Explain any method of measuring unknown impedance. How unknown frequency can be measured using direct reading frequency meter (DRFM)?

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