Correct Answer :   increases

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Explanation : Charging current and MVAR are proportional to frequency.

Correct Answer :   intermediate cavity

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Explanation : A Klystron is a vacuum tube used for generation/amplification of microwaves.

An electron beam is produced by oxide coated indirectly heated cathode and is focussed and accelerated by focussing electrode.

This beam is transmitted through a glass tube. The input cavity where the beam enters the glass tube is called buncher.

As electrons move ahead they see an accelerating field for half cycle and retarding field for the other half cycle.

Therefore, some electrons are accelerated and some are retarded. This process is called velocity modulation.

The velocity modulation causes bunching of electrons. This bunching effect converts velocity modulation into density modulation of beam.

The input is fed at buncher cavity and output is taken at catcher cavity.

In a two cavity klystron only buncher and catcher cavity are used. In multi cavity klystron one or more intermediate cavities are also used.

The features of a multicavity klystron are :

1. Frequency range - 0.25 GHz to 100 GHz

2. Power output - 10 kW to several hundred kW

3. Power gain - 60 dB (nominal value)

4. Efficiency - about 40%.

A multicavity klystron is used in UHF TV transmitters, Radar transmitter and satellite communication.

Correct Answer :   All of the above

Correct Answer :   The shortest possible time

Correct Answer :   electrical size

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Explanation : Circuit theory assumes physical dimensions of the network smaller than electrical wavelength, while transmission lines may be considerable fraction of wavelength.

Correct Answer :   distributed

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Explanation : Since no lumped elements like resistors, capacitors are used at microwave frequencies, only transmission lines are used. Hence they are called distributed parameter network.

Correct Answer :   2 conductors

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Explanation : With a single conductor, transverse electromagnetic wave propagation is not possible. Hence we need a minimum of 2 conductors.

Correct Answer :   1°

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Explanation : For ideal dielectric loss angle is zero. For good quality cables, loss angle is very small, about 1° only.

Correct Answer :   isolation (dB) equals coupling plus directivity

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Explanation : Isolation equals coupling plus directivity.

Correct Answer :   relative permittivity of dielectric

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Explanation :

∈_r of a dielectric changes with humidity.

Correct Answer :   buncher

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Explanation : A Klystron is a vacuum tube used for generation/amplification of microwaves.

An electron beam is produced by oxide coated indirectly heated cathode and is focussed and accelerated by focussing electrode.

This beam is transmitted through a glass tube. The input cavity where the beam enters the glass tube is called buncher.

As electrons move ahead they see an accelerating field for half cycle and retarding field for the other half cycle.

Therefore, some electrons are accelerated and some are retarded. This process is called velocity modulation.

The velocity modulation causes bunching of electrons. This bunching effect converts velocity modulation into density modulation of beam.

The input is fed at buncher cavity and output is taken at catcher cavity.

In a two cavity klystron only buncher and catcher cavity are used. In multi cavity klystron one or more intermediate cavities are also used.

The features of a multicavity klystron are :

1. Frequency range - 0.25 GHz to 100 GHz

2. Power output - 10 kW to several hundred kW

3. Power gain - 60 dB (nominal value)

4. Efficiency - about 40%.

A multicavity klystron is used in UHF TV transmitters, Radar transmitter and satellite communication.

Correct Answer :   TE₁₁

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Explanation :

Some applications require dual polarization capability. Circular waveguide has this capability.

These analysis uses cylindrical coordinates.

In circular waveguide TE₁₁ mode has the lowest cut off frequency and is the dominant mode.

If D is diameter of waveguide

λ_c = 1.706 D for TE₁₁ mode

λ_c = 1.029 D for TE₂₁ mode

λ_c = 0.82 D for TE₀₁ mode

λ_c = 1.306 D for TM₀₁ mode.

Correct Answer :   All of the above

Correct Answer :   increases exponentially

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Explanation : In a klystron the resonant structure limits the bandwidth.

A TWT is a broadband device. Its main components are electron gun (to produce the electron beam) and a structure supporting the slow electromagnetic wave.

The velocity of wave propagation along the helix structure is less than velocity of light.

The beam and wave travel along the structure at the same speed.

Thus interaction occurs between beam and wave and the beam delivers energy to the RF wave.

Therefore the signal gets strengthened and amplified output is delivered at the other end of tube.

The main features of TWT are :

1. Frequency range - 0.5 GHz to 90 GHz

2. Power output - 5 mW at low frequencies(less than 20 GHz) 250 kW (continuous wave) at 3 GHz 10 MW (pulsed) at 3 GHz

3. Efficiency - about 5 to 20%

4. Noise - about 5 dB for low power TWT 25 dB for high power TWT

TWT is used as RF amplifier in broadband microwave receivers, repeater amplifier in broad band communication systems, communication satellites etc.

Correct Answer :   As a second anode and to prevent the build-up of secondary field

Correct Answer :   Ferrite emitter

Correct Answer :   By bunches of electrons passing the cavity grids

Correct Answer :   Indicates both the range and azimuth of a target

Correct Answer :   All of the above

Correct Answer :   Magnetron

Correct Answer :   transistor

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Explanation : In the lumped element circuit model of a transmission line, we use only resistor, capacitor and inductor. Hence no transistor is used.

Correct Answer :   impedance which is a constant at any point on the transmission line

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Explanation : Characteristic impedance is defined as that impedance of a line which is a constant when measured at any point on the line

Correct Answer :   imaginary value

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Explanation : Since propagation constant is a complex value, containing attenuation constant α, phase constant β respectively as their real and imaginary parts.

Correct Answer :   Both (A) and (B)

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Explanation : α is the real value of propagation constant, also signifies the loss that the transmission line causes and hence the total amount of energy transmitted. Hence all the mentioned.

Correct Answer :   0

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Explanation : α-for a transmission line signifies the attenuation constant. For a lossless transmission line attenuation constant is zero and the propagation occurs without losses.

Correct Answer :   α=6, β=10.39

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Explanation : The given propagation constant is in polar form .converting from polar form to rectangular form and equating the real and imaginary parts, we get α=6 and β=10.39.

Correct Answer :   0

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Explanation : β=ω√LC. Since both the line impedance and line admittance are both real, there is no phase difference caused and hence substituting in the above equation, we get β=0.

Correct Answer :   0.0654 +j0.48

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Explaination : Z=R+jωL and Y=G+jωC, hence finding out Z and Y from these equations, substituting in γ=√ZY, value of γ is found out to be 0.0654+j0.48.

Correct Answer :   0.035+j41.97

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Explaination : Impedance Z of a transmission line is given by the product of propagation constant γ and characteristic Zâ‚’, Z= γZâ‚’ , we get Z=0.035+j41.97.

Correct Answer :   TEM, TE, TM modes

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Explanation : Parallel plate waveguide is the simplest type of waveguide that can support TE and TM modes. It can also support a TEM mode since it is formed from two flat conducting plates.

Correct Answer :   Width of the plates is greater than the distance between the plates

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Explanation : The strip width W of the parallel plate waveguide is assumed to be much greater than the separation d, hence the fringe effect or the fringing fields can be neglected.

Correct Answer :   62.833 Ω

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Explaination : The expression for intrinsic impedance of a parallel plate waveguide is η*D/W. substituting the given values of intrinsic impedance and distance between plates and width of the plates, intrinsic impedance is 62.833Ω.

Correct Answer :   Function of frequency

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Explanation : The wave impedance of a parallel plate waveguide in TM mode is β/k which is a function of frequency. The wave impedance is real for f>fC and purely imaginary for f<fC.

Correct Answer :   Real

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Explanation : The phase velocity and guide wavelength for a parallel plate waveguide are defined only for propagating modes. Propagating modes are those modes for which β are always positive. Hence β is always real for a parallel plate waveguide.

Correct Answer :   40 mm

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Explanation : The cutoff wavelength of a TMn mode in a parallel plate waveguide is 2d/n, where d is the distance between the plates and n signifies the mode of operation. For the given condition, substituting the given values, cut off wavelength is 40 mm.

Correct Answer :   TM1 mode

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Explanation : The mode of propagation for which the cutoff wavelength for wave propagation is maximum is called dominant mode. In TM mode of propagation, TM0 mode is similar to TEM mode of propagation. Hence, TM1 mode is the dominant mode.

Correct Answer :   No real power flow occurs in the ‘z’ direction

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Explanation : The superposition of the two plane waves in Z direction is such that complete cancellation occurs at y=0 and y=d, to satisfy the boundary conditions that Ez=0 at these planes. As f decrease to fc, β approaches 0 so that θ approaches 90⁰. The two plane waves are then bouncing up and down, with no motion in +z direction, and no power flow occurs in the z direction.

Correct Answer :   Imaginary

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Explanation : Wave impedance of a parallel plate waveguide for TEN modes is k/β. This expression is valid and real only for propagating modes. For non propagating modes, impedance becomes imaginary.

Correct Answer :   Coaxial

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Explanation : Since fields are confirmed within a coaxial cable it is non-radiating.

Correct Answer :   TWT

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Explanation : In a klystron the resonant structure limits the bandwidth.

A TWT is a broadband device. Its main components are electron gun (to produce the electron beam) and a structure supporting the slow electromagnetic wave.

The velocity of wave propagation along the helix structure is less than velocity of light.

The beam and wave travel along the structure at the same speed.

Thus interaction occurs between beam and wave and the beam delivers energy to the RF wave.

Therefore the signal gets strengthened and amplified output is delivered at the other end of tube.

The main features of TWT are :

1. Frequency range - 0.5 GHz to 90 GHz

2. Power output - 5 mW at low frequencies(less than 20 GHz) 250 kW (continuous wave) at 3 GHz 10 MW (pulsed) at 3 GHz

3. Efficiency - about 5 to 20%

4. Noise - about 5 dB for low power TWT 25 dB for high power TWT

TWT is used as RF amplifier in broadband microwave receivers, repeater amplifier in broad band communication systems, communication satellites etc.

Correct Answer :   G

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Explanation : Shunt conductance can be neglected in most of calculations.

Correct Answer :   apple gate diagram

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Explanation : Applegate diagram is distance time plot.

Correct Answer :   L and C in series

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Explanation : A quarter wave line o.c. at far end behaves as a series tuned circuit.

Correct Answer :   varying the voltage which controls beam velocity

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Explanation : It is somewhat similar to TWT and can deliver microwave power over a wide frequency band.

It has an electron gun and a helix structure. However the interaction between electron beam and RF wave is different than in TWT.

The growing RF wave travels in opposite direction to the electron beam.

The frequency of wave can be changed by changing the voltage which controls the beam velocity.

Moreover the amplitude of oscillations can be decreased continuously to zero by changing the beam current.

It features are :

1. Frequency range - 1 GHz to 1000 GHz.

2. Power output - 10 mV to 150 mW (continuous wave) 250kW (pulsed).

It is used as signal source in transmitters and instruments.

Correct Answer :   0.21 m

Correct Answer :   40 ns

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Explaination :

Correct Answer :   printed circuit technique

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Explanation : Printed circuit techniques is used for micro strip line.

Correct Answer :   the oscillations will continue indefinitely

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Explanation :

Correct Answer :   400 Ω

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Explanation :

Correct Answer :   0.5 W, 0.5 W, 0 W

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Explaination :

Since all ports matched, input SWR = 1. No power is reflected and P_in = P₄ = 1 W.

This power splits between ports 1 and 2. Therefore P₁ = P₂ = 0.5 Ω, P₃ = 0.

Correct Answer :   90° out of phase with each other

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Explanation : Since the two wire radiators are at 90° to each other, they have to be excited 90° out of phase with each other.

Correct Answer :   HP filter

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Explanation : It allows high frequencies.

Correct Answer :   guide diameter

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Explanation :

Some applications require dual polarization capability. Circular waveguide has this capability.

These analysis uses cylindrical coordinates.

In circular waveguide TE₁₁ mode has the lowest cut off frequency and is the dominant mode.

If D is diameter of waveguide

λ_c = 1.706 D for TE₁₁ mode

λ_c = 1.029 D for TE₂₁ mode

λ_c = 0.82 D for TE₀₁ mode

λ_c = 1.306 D for TM₀₁ mode.

Correct Answer :   its cross-sectional area

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Explanation :

Correct Answer :   cathode, buncher cavity, catcher cavity, cavity

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Explanation : Cathode is the first part and anode is the last.

Correct Answer :   SONAR

Correct Answer :   10 GHz

Correct Answer :   Reduce interference from the effects of sea return

Correct Answer :   Large reflector

Correct Answer :   Towards the earth

Correct Answer :   3000 to 30000 MHz

Correct Answer :   Co-axial cable

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Explanation : Coaxial cables support TEM mode of propagation in them and rectangular waveguide, circular wave guide, surface waveguides do not support TEM mode of propagation in them.

Correct Answer :   [V] = [Z][I]

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Explanation : In microwave networks, at any point in a network, the voltage at a point is the product of the impedance at that point and current measured. This can be represented in the form of a matrix.

Correct Answer :   [I] = [Y] [V]

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Explanation : The relation between voltage current and admittance matrices is [I] = [Y] [V]. here I represents the current matrix, Y is the admittance matrix and V is the voltage matrix.

Correct Answer :   Purely imaginary

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Explanation : For a network to be lossless, the network should be purely imaginary. Presence of any real component implies the presence of resistance in the network from which the network becomes lossy. So the matrices must be purely imaginary.

Correct Answer :   Symmetric matrix

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Explanation : For a reciprocal matrix, the impedance measured at port Z_ij is equal to the impedance measured at port Z_ji. Since these parameters occupy symmetric positions in the Z matrix, the matrix becomes symmetric.

Correct Answer :   Indecent and the reflected voltage waves

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Explanation : S matrix can be used to represent any n port network. S parameters are defined for microwave networks. Hence instead of voltage and current measurement, the amplitude of the incident and reflected voltage waves is measured.

Correct Answer :   [v-] = [s] [v+].

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Explanation : S parameter for a microwave network is defined as the ratio of reflected voltage wave to the incident voltage wave. When represented in the form of a matrix, reflected voltage matrix is the product of S parameter and the incident voltage wave at that port.

Correct Answer :   Network analyzer

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Explanation : Network analyzer is a device to which any microwave network can be externally connected with the help of probes and the s parameters of the network can be obtained.

Correct Answer :   Symmetric

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Explanation : For a reciprocal network, the input to port I and output at port j is the same as the input at port j and output measured at port i. Hence, the ports are interchangeable. As the ports are interchangeable, this is reflected in the matrix and the matrix becomes symmetric.

Correct Answer :   Unitary

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Explanation : For a lossless network, the scattering matrix has to be unitary. That is, the law of conservation of energy is to be verified for this case. Using appropriate formula, this condition can be verified.

Correct Answer :   6.020 dB

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Explanation : Given the reflection coefficient of the network, return loss of the network is calculated using the formula -20 log │Г│. Substituting for reflection coefficient, the return loss of the network is 6.02 dB.

Correct Answer :   12.05 dB

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Explanation : Given the reflection coefficient of the network, return loss of the network is calculated using the formula -20 log │Г│. Substituting for reflection coefficient, the return loss of the network is 12.05 dB.

Correct Answer :   When there is two or more port networks in the cascade

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Explanation : The Z, Y, and S parameter representation can be used to characterize a microwave network with an arbitrary number of ports. But most microwave networks consist of cascade of two or more two port networks. In this case it is convenient to use ABCD matrix for network representations.

Correct Answer :   Product of ABCD matrices representing the individual two ports

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Explanation : When two networks are connected in cascade, each of the two networks are represented as a 2×2 square matrix. Then to obtain the equivalent matrix of the cascade, the product of the ABCD matrices of each stage is taken.

Correct Answer :   A=1, Z=B, C=0, D=1

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Explanation : If simple impedance or an equivalent impedance of a network is represented as a ABCD matrix, writing the equations in terms of voltage and current and setting each variable to zero, the four constants are obtained. For an impedance Z, the constants are A=1, Z=B, C=0, D=1.

Correct Answer :   A=1, B=0, C=Y, D=1

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Explanation : If simple admittance or an equivalent admittance of a network is represented as a ABCD matrix, writing the equations in terms of voltage and current and setting each variable to zero, the four constants are obtained. For an admittance Y, the constants are A=1, Z=B, C=0, D=1.

Correct Answer :   2

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Explanation : Z₁₁ parameter of a two port network is the ratio of the A parameter of the network to the B parameter of the network. Taking the ratio of the given values, Z₁₁ is 2.

Correct Answer :   2.5

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Explaination : For a two port network, B parameter is defined as the reciprocal of the admittance Y₁₂. Taking the reciprocal of the given value, the B parameter of the network is 2.5.

Correct Answer :   Loss in the resonant circuit

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Explanation : Quality factor of a resonant network is defined as the ratio of average energy stored to the energy loss/ second. Hence, lower loss implies a higher quality factor.

Correct Answer :   Unloaded Q> external Q

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Explaination : To compute unloaded Q only the resistance in the resonant circuit is considered. But to calculate external Q, the resistance and other load in the external load is also considered. Sine Q and R are inversely proportional, as R increases Q decreases. Since R is greater for external Q computation, unloaded Q> external Q.

Correct Answer :   0.005

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Explanation : The relation between quality factor and bandwidth is given as bandwidth=Q-1. Substituting for bandwidth in this expression, the quality factor of the resonant circuit is 0.005.

Correct Answer :   6.4mW

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Explaination : The power loss in a parallel RLC circuit is 0.5│V│2/R. given the values of source voltage and resistance in the circuit, the power loss in the parallel RLC circuit is 6.4mW.

Correct Answer :   False

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Explanation : Band width and quality factor of a series RLC circuit are both inversely related. Higher the quality factor, lower the operating bandwidth.

Correct Answer :   shorted at both the ends

---

Explanation : A cylindrical cavity resonator is formed by shorting both the ends of the cylindrical cavity because open ends may result in radiation losses in the cavity.

Correct Answer :   151

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Explanation : Wave number for a circular cavity resonator is given by the expression 2πf₀₁₁√∈_r/C. substituting the given values in the above expression; the wave number of the cavity resonator is 151.

Correct Answer :   2500

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Explanation : Unloaded Q due to the dielectric loss in a circular cavity resonator is the reciprocal of the loss tangent. Hence, taking the reciprocal of the loss tangent, unloaded Q due to dielectric loss is 2500.

Correct Answer :   29390

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Explaination : Unloaded Q of a circular resonator due to conductor loss is given by ka/2R_s. is the intrinsic impedance of the medium. Substituting the given values in the equation for loaded Q, value is 29390.

Correct Answer :   2300

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Explaination : The total unloaded Q of a circular cavity resonator is given by the expression (Q_c^-1+ Q_d^-1)^-1. Substituting the given values in the above expression, the total unloaded Q for the resonator is 2300.

Correct Answer :   β/2α

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Explanation : Quality factor of a short circuited transmission line is a function of attenuation constant and phase constant of the transmission line. Higher is the attenuation in the transmission line, lower is the quality factor of the transmission line.

Correct Answer :   783

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Explaination : Unloaded Q for a microstrip line is given by β/2α. Α is the sum of attenuation due to conductor loss and dielectric loss. Substituting the given values the equation, unloaded Q is 783.

Correct Answer :   0.0724

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Explaination : Attenuation due to conductor loss of a microstrip line is given by R_s/Z₀W. Substituting the given values, attenuation due to conductor loss is 0.0724 Np/m.

Correct Answer :   0.011

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Explaination : Conductor loss in a coaxial cable is given by R_s(a^-1+b^-1)/2ln (b/a). Here ‘a’ and ‘b’ are the inner and outer radii of the coaxial cable. is the intrinsic impedance of the medium, for air is 377Ω. Substituting the given values in the equation, conductor loss is 0.022 Np/m.

Correct Answer :   2380

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Explaination : Quality factor of a λ/2 short circuited transmission line is β/2α. β is the phase constant and α is the attenuation constant of the line, substituting the given values, the quality factor of the transmission line is 2380.

Correct Answer :   coupling coefficient

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Explanation : Coupling coefficient tells how the resonator is coupled to the external circuitry. A resonator can be coupled in three ways. They can be under coupled, critically coupled or over coupled.

Correct Answer :   resonant frequency

---

Explanation : In order to obtain a maximum power transfer between a resonator and a feed line, the resonator should be matched to the feed line at the resonant frequency of the resonator which is coupled.

Correct Answer :   critically coupled

---

Explanation : The resonator is critically coupled to the feed line when the coupling coefficient is 1. Maximum power is transferred between the resonator and the feed line since the resistance of the resonator is equal to the characteristic impedance of the transmission line.

Correct Answer :   shunt inductance

---

Explanation : In aperture coupling, a small aperture is made in the transverse wall of the cavity which is to be coupled to an external microwave circuit. This aperture made in the transverse wall of the cavity acts as a shunt inductance.

Correct Answer :   TE, TM modes of resonance

---

Explanation : A rectangular wave guide supports both TE and TEM mode of propagation. Likewise, when a rectangular waveguide is used as resonator, it supports both TE and TM modes of resonance.

Correct Answer :   Helmholtz equation

---

Explanation : Helmholtz wave equation is considered and solved using variable separable form. Then the boundary conditions are applied to the wave equation considering the walls of the cavity. Solving this gives the expression for resonant frequency.

Correct Answer :   Defined as the ratio of stored energy to the power dissipated in the walls

---

Explanation : Quality factor signifies the power loss in the circuit. It is defined as the ratio of stored energy to the power dissipated in the walls. Higher the power dissipation in the walls, lower is the quality factor of the waveguide resonator.

Correct Answer :   157.08

---

Explanation : The wave number of rectangular wave resonator is 2πf√∈r/C, substituting the given values in the above equation, the wave number of the rectangular cavity resonator is 157.08.

Correct Answer :   2500

---

Explanation : Q of a rectangular waveguide due to dielectric loss is given by 1/tanδ. Substituting for tanδ in the above equation, Q due to dielectric loss is 2500.

Correct Answer :   2.20 cm

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Explaination : The required length of the cavity resonator for the given mode is given by the expression d=lπ/√(k>sup>2-(π/a)². Substituting the given values in the equation, the required length of the waveguide is 2.20 cm.

Correct Answer :   False

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Explaination : For the given dimensional specification b<a<d, the dominant resonant mode (lowest resonant frequency) will be the TE101 mode, corresponding to the TE10 dominant waveguide mode in a shorted guide of length λg/2.

Correct Answer :   False

---

Explanation : For resonance to occur in waveguides, a closed structure is required. They resonate between the walls of the rectangular waveguide. Also radiation loss from an open ended waveguide can be significant.

Correct Answer :   negative potential

---

Explanation : It uses a single cavity resonator for generating microwave oscillations.

Its parts are electron gun, resonator, repeller and output coupling.

It operates on the principle of positive feed back.

The repeller electrode is at negative potential and sends the partially bunched electron beam back to resonator cavity.

This positive feedback supports oscillations. Its feature are :

1. Frequency range - 2 to 100 GHz

2. Power output - 10 MW to about 2 W

3. Efficiency - 10 - 20 %

Its applications include radar receivers, local oscillator in microwave devices, oscillator for microwave measurements in laboratories etc.

Correct Answer :   an inductance and capacitance in parallel

---

Explanation : A quarter wave line short-circuited at far end behaves as a parallel tuned circuit.

Correct Answer :   50°

---

Explanation :

Correct Answer :   Gunn diode

---

Explanation : A Gunn diode uses GaAs which has a negative differential mobility, i.e., a decrease in carrier velocity with increase in electric field.

This effects is called transferred electron effect. The impedance of a Gunn diode is tens of ohms.

A Gunn diode oscillator has a resonant cavity, an arrangement to couple Gunn diode to cavity, biasing arrangement for Gunn diode and arrangement to couple RF power to load.

Applications of Gunn diode oscillator include continuous wave radar, pulsed radar and microwave receivers.

Correct Answer :   Allow the transmitter and the receiver to operate from a common antenna

Correct Answer :   Velocity modulation at the input cavity creates density modulation at the output cavity

Correct Answer :   Its resonant cavity

Correct Answer :   Isolator

Correct Answer :   Slow fading

Correct Answer :   1 to 100 GHz

Correct Answer :   Both (B) and (C)

Correct Answer :   Attenuation

Correct Answer :   Magnetron

Correct Answer :   far end

---

Explanation : When a line is short-circuited at far end, the voltage at far end is zero.

Correct Answer :   20 dB more

---

Explanation : As frequency increases, transmission loss increases slightly.

Correct Answer :   at a velocity that is a small fraction of speed of light

---

Explanation : In a klystron the resonant structure limits the bandwidth.

A TWT is a broadband device. Its main components are electron gun (to produce the electron beam) and a structure supporting the slow electromagnetic wave.

The velocity of wave propagation along the helix structure is less than velocity of light.

The beam and wave travel along the structure at the same speed.

Thus interaction occurs between beam and wave and the beam delivers energy to the RF wave.

Therefore the signal gets strengthened and amplified output is delivered at the other end of tube.

The main features of TWT are :

1. Frequency range - 0.5 GHz to 90 GHz

2. Power output - 5 mW at low frequencies(less than 20 GHz) 250 kW (continuous wave) at 3 GHz 10 MW (pulsed) at 3 GHz

3. Efficiency - about 5 to 20%

4. Noise - about 5 dB for low power TWT 25 dB for high power TWT

TWT is used as RF amplifier in broadband microwave receivers, repeater amplifier in broad band communication systems, communication satellites etc.

Correct Answer :   cutoff frequency for TE10 and TE01 modes are same

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Explanation : When a circular waveguide is rotated by 90°, the configuration remain the same.

Correct Answer :   SWR is finite

Correct Answer :   50 Ω

Correct Answer :   Both (A) and (B)

Correct Answer :   pulses with very small width

---

Explanation : High speed means time period is small. Therefore pulses should also have small width.

Correct Answer :   balun

---

Explanation : A balun gives 4 : 1 impedance transformation.

Correct Answer :   low SWR at both ports

---

Explanation : Turn ratio is so selected as to give low SWR at both ports.

Correct Answer :   inversely proportional to square of wavelength

Correct Answer :   use an antenna for reception or transmission without interference

---

Explanation : Same antenna is used for transmission and reception.

Correct Answer :   travelling along the line winds itself back and forth

---

Explanation : It is somewhat similar to TWT and can deliver microwave power over a wide frequency band.

It has an electron gun and a helix structure. However the interaction between electron beam and RF wave is different than in TWT.

The growing RF wave travels in opposite direction to the electron beam.

The frequency of wave can be changed by changing the voltage which controls the beam velocity.

Moreover the amplitude of oscillations can be decreased continuously to zero by changing the beam current.

It features are :

1. Frequency range - 1 GHz to 1000 GHz.

2. Power output - 10 mV to 150 mW (continuous wave) 250kW (pulsed).

It is used as signal source in transmitters and instruments.

Correct Answer :   Both TR and ATR tube

---

Explanation : A branched duplexer funds use in narrow bandwidth applications.

TR tube stands for transmit-receive tube and ATR tube stands for antitransmit receive tube.

Both these tubes are used in branched duplexer.

Correct Answer :   broad bandwidth

---

Explanation : Since reactance does not contribute thermal noise to the circuit, it is a low noise device.

Correct Answer :   high frequencies

---

Explanation : At high frequencies transit time is large as compared to the period of microwave signal.

Correct Answer :   100 watts

Correct Answer :   Must be increased

Correct Answer :   The dimension of each cavity resonator

Correct Answer :   Which may be used to tune the radar receiver

Correct Answer :   Adjusting the flexible wall of the resonant cavity

Correct Answer :   a hollow metallic enclosure

---

Explanation : Hollow metallic enclosures exhibit resonance behaviour when excited by electromagnetic field.

These enclosures are called cavity resonators.

Correct Answer :   at microwave frequencies

---

Explanation : Atomic and molecular distances are very small. Therefore resonance can occur only at microwave frequencies.

Correct Answer :   PIN diode

---

Explanation : A PIN diode has an intrinsic (i) layer between p and n layers. When reverse bias is applied depletion layers are formed at p-i and i-n junctions.

The effective/width of depletion layer increases by the width of i layer. It can be used as a voltage controlled attenuator.

At high frequencies the rectification effect ceases and impedance of diode is effectively that of i layer.

This impedance varies with the applied bias. It is used in high frequency switching circuits, limiters, modulators etc.

Correct Answer :   0.47 dB/m

---

Explanation : 0.054 x 8.68 = 0.47 dB/m.

Correct Answer :   one cavity resonator

---

Explanation : It uses a single cavity resonator for generating microwave oscillations.

Its parts are electron gun, resonator, repeller and output coupling.

It operates on the principle of positive feed back.

The repeller electrode is at negative potential and sends the partially bunched electron beam back to resonator cavity.

This positive feedback supports oscillations.

Its feature are :

1. Frequency range - 2 to 100 GHz

2. Power output - 10 MW to about 2 W

3. Efficiency - 10 - 20 %

Its applications include radar receivers, local oscillator in microwave devices, oscillator for microwave measurements in laboratories etc.

Correct Answer :   0.1 μ H/m

---

Explanation :

Correct Answer :   Either (A) or (B)

---

Explanation :

Correct Answer :   50

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Explanation : A TV channel has a bandwidth about 5 MHz. Hence 300 MHz spectrum can accommodate about 50 channels.

Correct Answer :   The radial lines are E lines and circular lines are H lines

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Explaination : H lines are concentric circles around conductor and E lines are radial.

Correct Answer :   about one-tenth

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Explanation : Time required for microwave cooking is much less than the time required for conventional cooking.

Correct Answer :   16

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Explanation :

Range = (power)⁰²⁵.

Correct Answer :   low power device

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Explanation : It uses a single cavity resonator for generating microwave oscillations.

Its parts are electron gun, resonator, repeller and output coupling.

It operates on the principle of positive feed back.

The repeller electrode is at negative potential and sends the partially bunched electron beam back to resonator cavity.

This positive feedback supports oscillations.

Its feature are :

1. Frequency range - 2 to 100 GHz

2. Power output - 10 MW to about 2 W

3. Efficiency - 10 - 20 %

Its applications include radar receivers, local oscillator in microwave devices, oscillator for microwave measurements in laboratories etc.

Correct Answer :   a quarter wave line

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Explanation : Impedance inversion occurs when load impedance is not matched with characteristic impedance of line.

Correct Answer :   more than 30 dB

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Explanation : A Klystron is a vacuum tube used for generation/amplification of microwaves.

An electron beam is produced by oxide coated indirectly heated cathode and is focussed and accelerated by focussing electrode.

This beam is transmitted through a glass tube. The input cavity where the beam enters the glass tube is called buncher.

As electrons move ahead they see an accelerating field for half cycle and retarding field for the other half cycle.

Therefore, some electrons are accelerated and some are retarded. This process is called velocity modulation.

The velocity modulation causes bunching of electrons. This bunching effect converts velocity modulation into density modulation of beam.

The input is fed at buncher cavity and output is taken at catcher cavity.

In a two cavity klystron only buncher and catcher cavity are used. In multi cavity klystron one or more intermediate cavities are also used.

The features of a multicavity klystron are :

1. Frequency range - 0.25 GHz to 100 GHz

2. Power output - 10 kW to several hundred kW

3. Power gain - 60 dB (nominal value)

4. Efficiency - about 40%.

A multicavity klystron is used in UHF TV transmitters, Radar transmitter and satellite communication.

Correct Answer :   Loran C: 100 kHz

Correct Answer :   The interval between transmitted pulses

Correct Answer :   All of the above

Correct Answer :   No noticeable effect

Correct Answer :   Slow fading

Correct Answer :   The absorption of energy by the signal from an electron stream

Correct Answer :   1, 2 and 3 only

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Explaination : A Klystron is a vacuum tube used for generation/amplification of microwaves.

An electron beam is produced by oxide coated indirectly heated cathode and is focussed and accelerated by focussing electrode.

This beam is transmitted through a glass tube. The input cavity where the beam enters the glass tube is called buncher.

As electrons move ahead they see an accelerating field for half cycle and retarding field for the other half cycle.

Therefore, some electrons are accelerated and some are retarded. This process is called velocity modulation.

The velocity modulation causes bunching of electrons. This bunching effect converts velocity modulation into density modulation of beam.

The input is fed at buncher cavity and output is taken at catcher cavity.

In a two cavity klystron only buncher and catcher cavity are used. In multi cavity klystron one or more intermediate cavities are also used.

The features of a multicavity klystron are :

1. Frequency range - 0.25 GHz to 100 GHz

2. Power output - 10 kW to several hundred kW

3. Power gain - 60 dB (nominal value)

4. Efficiency - about 40%.

A multicavity klystron is used in UHF TV transmitters, Radar transmitter and satellite communication.

Correct Answer :   Varactor diode

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Explanation : Gunn diode, Tunnel diode and Impatt diodes are negative resistance devices.

The limitation of solid state devices at high frequencies include those associated with transit time and junction capacitances.

The devices used are : Transferred electron oscillators (Gunn diode), Avalanche diode oscillators (Impatt diode, Trapatt diode, Masters, Lasers, Tunnel diode, Varactor etc).

Correct Answer :   coplanar arms are coupled

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Explanation : Coplanar arms are decoupled.

Correct Answer :   double stub

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Explanation : Double stub is useful for matching over a range of frequencies.

Correct Answer :   because of earth's curvature

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Explanation : Earth's curvature limits the distance between microwave links.

Correct Answer :   0.001

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Explanation :

1 x 10^-6 x 1000 = 0.001.

Correct Answer :   Reflex klystron amplifier

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Explanation : A Klystron is a vacuum tube used for generation/amplification of microwaves.

An electron beam is produced by oxide coated indirectly heated cathode and is focussed and accelerated by focussing electrode.

This beam is transmitted through a glass tube. The input cavity where the beam enters the glass tube is called buncher.

As electrons move ahead they see an accelerating field for half cycle and retarding field for the other half cycle.

Therefore, some electrons are accelerated and some are retarded. This process is called velocity modulation.

The velocity modulation causes bunching of electrons. This bunching effect converts velocity modulation into density modulation of beam.

The input is fed at buncher cavity and output is taken at catcher cavity.

In a two cavity klystron only buncher and catcher cavity are used. In multi cavity klystron one or more intermediate cavities are also used.

The features of a multicavity klystron are :

1. Frequency range - 0.25 GHz to 100 GHz

2. Power output - 10 kW to several hundred kW

3. Power gain - 60 dB (nominal value)

4. Efficiency - about 40%.

A multicavity klystron is used in UHF TV transmitters, Radar transmitter and satellite communication.

Correct Answer :   is less than avalanche breakdown voltage

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Explanation : The action of varactor diode is due to the capacitance of depletion layer. The thickness of depletion layer depends on the reverse bias which should not cause breakdown.

Correct Answer :   0.707

Correct Answer :   coupling and directivity

Correct Answer :   1500

Correct Answer :   225 Ω

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Explaination :

Correct Answer :   long range navigation

Correct Answer :   (PRF) (pulse width)

Correct Answer :   7.5 mm

Correct Answer :   causes acceleration of some electrons and retardation of others

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Explanation : A Klystron is a vacuum tube used for generation/amplification of microwaves.

An electron beam is produced by oxide coated indirectly heated cathode and is focussed and accelerated by focussing electrode.

This beam is transmitted through a glass tube. The input cavity where the beam enters the glass tube is called buncher.

As electrons move ahead they see an accelerating field for half cycle and retarding field for the other half cycle.

Therefore, some electrons are accelerated and some are retarded. This process is called velocity modulation.

The velocity modulation causes bunching of electrons. This bunching effect converts velocity modulation into density modulation of beam.

The input is fed at buncher cavity and output is taken at catcher cavity.

In a two cavity klystron only buncher and catcher cavity are used. In multi cavity klystron one or more intermediate cavities are also used.

The features of a multicavity klystron are :

1. Frequency range - 0.25 GHz to 100 GHz

2. Power output - 10 kW to several hundred kW

3. Power gain - 60 dB (nominal value)

4. Efficiency - about 40%.

A multicavity klystron is used in UHF TV transmitters, Radar transmitter and satellite communication.

Correct Answer :   1.6 μ H/m

Correct Answer :   n resonant frequencies

Correct Answer :   0.25 Ω

Correct Answer :   decreases