# Multiple choice question for engineering

## Set 1

1. The major disadvantage of single stub tuning is:

a) it requires a variable length of line between the load and the stub

b) it involves 2 variable parameters

c) complex calculation

d) none of the mentioned

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2. The major advantage of double stub tuning is:

a) it uses 2 tuning stubs in fixed positions

b) it involves 2 stubs

c) length of the stub is variable

d) none of the mentioned

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3. In a double stub tuner circuit, the load is of _______ length from the first stub.

a) fixed length

b) arbitrary length

c) depends on the load impedance to be matched

d) depends on the characteristic impedance of the transmission line

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4. Double stub tuners are fabricated in coaxial line are connected in shunt with the main co-axial line.

a) true

b) false

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5. Impedance matching with a double stub tuner using a smith chart yields 2 solutions.

a) true

b) false

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6. All load impedances can be matched to a transmission line using double stub matching.

a) true

b) false

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7. The simplest method of reducing the forbidden range of impedances is:

a) increase the distances between the stubs

b) reduce the distance between the stubs

c) increase the length of the stubs

d) reduce the length of the stubs

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8. Stub spacing that are near 0 and λ/2 lead to more frequency sensitive matching networks.

a) true

b) false

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9. The standard stub spacing usually used is:

a) 0, λ/2

b) λ/4, λ/8

c) λ/8, 3λ/8

d) none of the mentioned

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10. If the length of the line between the first stub and the load can be adjusted, the admittance can be moved from the forbidden region.

a) true

b) false

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## Set 2

1. The level of coupling required between a resonator and its attached circuitry is a standard and independent of the application where coupling is required.

a) true

b) false

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2. A measure of the level of coupling between a resonator and a feed is given by:

a) coupling coefficient

b) power transfer coefficient

c) voltage coefficient

d) reflection coefficient

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3. To obtain maximum power transfer between a resonator and feed line, the resonator should be matched to the load at:

a) resonant frequency

b) cutoff frequency

c) zero frequency

d) none of the mentioned

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4. When impedance matching is done between a resonator and a feed line, the condition for impedance matching is:

a) R=Z_{0}

b) R=Z_{0}/2

c) R=2Z_{0}

d) R=√Z_{0}

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_{0}is the characteristic impedance of the feed line, for proper coupling their impedance has to be matched. This is the condition for impedance matching between a feed line and a resonator.

5. Coupling coefficient Q can be defined as the ratio of unloaded Q to external Q.

a) true

b) false

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6. When the coupling coefficient is lesser than one, the resonator is over coupled to the feed line.

a) true

b) false

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7. Direct measurement of the unloaded Q of a resonator is not possible.

a) true

b) false

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8. For practical applications cavity resonators can be modified as per the requirement of the application where it is used.

a) true

b) false

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9. When coupling coefficient is 1, the resonator is ________ to the feed line.

a) under coupled

b) over coupled

c) critically coupled

d) none of the mentioned

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10. In aperture coupling, a small aperture in the transverse wall of the waveguide acts as:

a) shunt inductance

b) shunt capacitance

c) series inductance

d) series capacitance

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## Set 3

1. The major disadvantage of binomial multi section transformer is higher bandwidth cannot be achieved.

a) true

b) false

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2. Advantage of chebyshev matching transformers over binomial transformers is:

a) higher gain

b) low power losses

c) higher roll-off in the characteristic curve

d) higher bandwidth

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3. There are passband ripples present in the chebyshev characteristic curve.

a) true

b) false

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4. Chebyshev matching transformers can be universally used for impedance matching in any of the microwave networks.

a) true

b) false

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5. The 4th order chebyshev polynomial is:

a) 8x^{4}-8x^{2}+1

b) 4x^{3}-4x^{2}+1

c) 4x^{3}-3x

d) none of the mentioned

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_{n}(x) = 2xT

_{n-1}(x) – T

_{n-2}(x). T

_{2}(x) = 2x

^{2}-1, T

_{3}(x)= 4x

^{3}-3x. Substituting the lower level polynomials in the given expression, T4(x) = 8x

^{4}-8x

^{2}+1.

6. Chebyshev polynomials do not obey the equal-ripple property.

a) true

b) false

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7. Chebyshev polynomial can be expressed in trigonometric functions as:

a) T_{n}(cos θ)=cos nθ

b) T_{n}(sin θ)= sin nθ

c) T_{n}(cos θ)=cos nθ.sin nθ

d) none of the mentioned

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8. For values of x greater than 1, the chebyshev polynomial in its trigonometric form cannot be determined.

a) true

b) false

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_{n}(x)=cosh (n cosh

^{-1}x).

9. Reflection co-efficient Гn in terms of Z_{n} and Z_{n+1}, successive impedances of successive sections in the matching network are:

a) 0.5 ln (Z_{n+1}/Z_{n})

b) 0.5 ln (Z_{n}/Z_{n+1})

c) ln (Z_{n+1}/Z_{n})

d) ln (Z_{n}/Z_{n+1})

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_{n+1}/Z

_{n}).

10. In a 3 section multisection chebyshev matching network, if Z_{3} = 100Ω, and Z_{2}=50Ω, then the reflection co-efficient Г_{2} is:

a) 0.154

b) 0.3465

c) 0.564

d) none of the mentioned

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_{n}for ‘n’ section matching chebyshev network is given by Г

_{n}=0.5 ln (Z

_{n+1}/Z

_{n}). substituting the given values in the expression, Г

_{2}is 0.3465.

11. If Г_{3}=0.2 and Z_{3}=50Ω, then the impedance of the next stage in the multi-section transformer is:

a) 100Ω

b) 50Ω

c) 74.6Ω

d) 22.3Ω

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_{n}=0.5 ln (Z

_{n+1}/Z

_{n}). Substituting the given values in the expression, the impedance of the next stage is Z

_{4}=74.6Ω.

## Set 4

1. ________ is a three-port microwave device that can be lossless and matched at all spots.

a) Hybrid junction

b) Magic Tee

c) Circulator

d) Isolator

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2. The total number of ones in the scattering matrix of an ideal circulator is:

a) 4

b) 3

c) 2

d) 5

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3. There is no method in which the scattering matrix of the opposite circularity can be obtained from the matrix we have.

a) True

b) False

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4. Practically, opposite circulatory in a ferrite circulator can be obtained by:

a) Changing the order of port operation

b) Impedance matching the input ports

c) Changing the polarity of the magnetic bias field

d) None of the mentioned

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5. A circulator device can also used as an isolator with a few modifications.

a) True

b) False

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6. In the scattering matrix representation of a non-ideal circulator, the diagonal elements of the matrix are:

a) Zero

b) One

c) Reflection coefficient Г

d) None of the mentioned

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7. In a stripline junction circulator, the ferrite material is present in the form of a:

a) Slab

b) Ferrite disk

c) Ferrite material is not used in a microstrip circulator

d) Ferrite cubes

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8. The dielectric resonator in the circulator has a single highest order resonant mode.

a) True

b) False

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9. In the plot of the magnitude of electric field around the periphery of the junction circulator, the curve has:

a) Three peaks

b) Two peaks

c) Four peaks

d) None of the mentioned

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10. In the non-ideal scattering matrix representation of the circulator, the attenuation constant and phase constant α, β respectively are approximated as 1.

a) True

b) False

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## Set 5

1. Ferrite isolators are ____ port microwave devices.

a) Two

b) Three

c) Four

d) None of the mentioned

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2. The matrix of an ideal isolator is not ______

a) Unitary

b) Symmetric

c) Lossless

d) None of the mentioned

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3. A very common application of isolator is to provide isolation between a low power source and the load.

a) True

b) False

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4. The attenuation of a ________ is very large near the gyro magnetic resonance of the ferrite.

a) Linearly polarized wave

b) Circularly polarized wave

c) Left polarized wave

d) Right polarized wave

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5. The isolators constructed using ferrite materials must operate at:

a) Gyro magnetic resonance

b) Magnetic resonance

c) Isolator resonance

d) None of the mentioned

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6. Forward attenuation provided by a resonance ferrite isolator is:

a) Zero

b) Low

c) High

d) None of the mentioned

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7. An isolator has a very large operating bandwidth and independent of any isolator parameter.

a) True

b) False

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8. The length of a ferrite slab required operating with a minimum forward insertion loss and 30 dB reverse attenuation and the reverse attenuation at this point is:

a) 3 cm

b) 2.4 cm

c) 4 cm

d) 3.6 cm

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9. The electric field distribution of the forward and reverse waves in a ferrite slab-loaded waveguide is quite different. This property is used in:

a) Field displacement resonator

b) Resonance isolator

c) Waveguide isolator

d) None of the mentioned

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10. Field displacement isolators require higher bias field than resonance isolators.

a) True

b) False