551 + Mcqs in Microwave Communication Page 1 McqOptions

1.	Characteristic impedance of a coaxial cable is inversely proportional to ∈r.
A.	True
B.	False
Answer» B. False

Discussion

2.	Assertion (A): In rectangular waveguide TE01 mode is just TE10 mode rotated by 90°.Reason (R): When a rectangular waveguide is rotated by 90°, the broad and narrow dimensions get interchanged.
A.	Both A and R are correct and R is correct explanation of A
B.	Both A and R are correct but R is not correct explanation of A
C.	A is correct but R is wrong
D.	A is wrong but R is correct
Answer» B. Both A and R are correct but R is not correct explanation of A

Discussion

3.	Consider the following applications SwitchAttenuatorPhase shifterOscillator In which of the above can a PIN diode be used?
A.	1 2 3 and 4
B.	1 2 and 3 only
C.	1 and 2 only
D.	2, 3 and 4 only
Answer» C. 1 and 2 only

Discussion

4.	In the given figure the equivalent circuit of a T attenuator. If the condition for matched attenuator is
A.	[A].
B.	[B].
C.	[C].
D.	[D].
Answer» B. [B].

Discussion

5.	A microstrip line has ∈r = 9. The normalised wavelength is about
A.	10
B.	2
C.	1
D.	0.4
Answer» E.

Discussion

6.	A circular waveguide carries TE11 mode whole radial electric field is given byEr = E0j1(r) sin Φ V/mwhere r is radial distance in cm from the axisThe cut off wavelength is
A.	10 cm
B.	3 p cm
C.	2 p cm
D.	8 cm
Answer» B. 3 p cm

Discussion

7.	Guide wavelength (λg), cutoff wavelength (λc) and free space wavelength (λ0) of a waveguide are related as
A.	[A].
B.	[B].
C.	[C].
D.	[D].
Answer» B. [B].

Discussion

8.	If ZTE is wave impedance for TE waves, Ed is maximum dielectric strength of insulating material, a and b are the width and height of a rectangular wave guide, the maximum power handling capability Pmax for TE10 mode is
A.	[A].
B.	[B].
C.	[C].
D.	[D].
Answer» C. [C].

Discussion

9.	If a and b are the width and height of rectangular wave-guide the cut off wavelength λc for TE20 mode is equal to
A.	a
B.	a + b
C.	a - b
D.	a2 + b2
Answer» B. a + b

Discussion

10.	For a rectangular waveguide having width a and height b, the cutoff wavelength for TM11 mode is equal to
A.	[A].
B.	[B].
C.	[C].
D.	[D].
Answer» C. [C].

Discussion

11.	If wavelength in free space is λ0 wavelength in insulator λ, μr is relative permittivity or insulator and ∈r is relative permittivity or insulator, then
A.	[A].
B.	[B].
C.	[C].
D.	[D].
Answer» C. [C].

Discussion

12.	If a line having Z0 = 300 ∠ 0 W is short circuited at far end, VSWR is
A.	0
B.	1
C.	∞
D.	2
Answer» D. 2

Discussion

13.	If a line having Z0 = 300 ∠ 0 W is open circuited at far end, VSWR is
A.	0
B.	1
C.	∞
D.	2
Answer» D. 2

Discussion

14.	If rv is reflection coefficient and VSWR is voltage standing wave ratio, then
A.	[A].
B.	[B].
C.	[C].
D.	[D].
Answer» C. [C].

Discussion

15.	The cavity resonator
A.	s equivalent to an LC resonant circuit
B.	n a reflect klystron has its output taken from the reflector plate
C.	roduces a frequency which is independent of the cavity size.
D.	as a low Q factor for narrow operation.
Answer» B. n a reflect klystron has its output taken from the reflector plate

Discussion

16.	Which of the following is used as a high power microwave oscillator?
A.	hyratron
B.	agnetron
C.	lystron
D.	eflex-klystron
Answer» C. lystron

Discussion

17.	A rectangular waveguide has two stubs each length λ/4 connected at the source end. The stubs are short circuted. Then
A.	the longitudinal current is power current and current in stubs is reactive
B.	the longitudinal current is reactive current and current in stubs is power current
C.	both power and reactive exists in both longitudinal direction and stubs
D.	the current in stubs is zero
Answer» B. the longitudinal current is reactive current and current in stubs is power current

Discussion

18.	A line of length slightly less than λ/4 and short circuited at far end behaves as
A.	inductance L
B.	capacitance C
C.	L and C in series
D.	L and C in parallel
Answer» B. capacitance C

Discussion

19.	Consider the following time parameters 1. Domain growth time constant.2. Transit time.3. Dielectric relaxation time in positive mobility regime. Which of the above are used in connection width transferred electron device?
A.	1, 2, and 3
B.	1 and 2 only
C.	1 and 3 only
D.	2 and 3 only
Answer» B. 1 and 2 only

Discussion

20.	Consider the following statements: 1. Impedance of Gunn diode is about tens of ohms.2. Impedance of Impatt diode is a few ohms.3. Impedance of Impatt diode are of the same order.4. Impedance of Impatt diode is more than that of Gunn diode. Which of the above statement are correct?
A.	all
B.	1 and 2 only
C.	1, 2 and 3
D.	1, 2 and 4
Answer» C. 1, 2 and 3

Discussion

21.	In a turnstile antenna two-half wave resonant wire radiators are placed at 90° to each other in the same plane and are excited
A.	in phase
B.	in phase opposition
C.	90° out of phase with each other
D.	45° out of phase with each other
Answer» D. 45° out of phase with each other

Discussion

22.	A line of characteristic impedance Z₀ branches into two line each with characteristic impedance Z₀. The refracted voltage is
A.	zero
B.	infinite
C.	equal to incident voltage
D.	two third of incident voltage
Answer» E.

Discussion

23.	What is the numerical aperture an optical fiber when critical angle is 30°?
A.	0.5
B.	0.704
C.	0.866
D.	0.2
Answer» B. 0.704

Discussion

24.	Out of modes TE₂₀ and TE₃₀ of propagation of electromagnetic engery
A.	both have the same cutoff frequency
B.	TE₂₀ has lower cut off frequency as compared to TE₃₀
C.	TE₃₀ has lower cutoff frequency as compared to TE₂₀
D.	either (a) or (c)
Answer» C. TE₃₀ has lower cutoff frequency as compared to TE₂₀

Discussion

25.	A line of characteristic impedance 400 Ω is terminated by a resistance of 400 Ω. The reflected quantities are
A.	zero
B.	equal to incident quantities
C.	half the incident quantities
D.	double the incident quantities
Answer» B. equal to incident quantities

Discussion

26.	To ensure that only dominant TE₁₀ mode propagates in a rectangular waveguide, the operating frequency
A.	must be more than cutoff frequency of TE₁₀ mode
B.	must be less than cutoff frequency of TE₂₀ mode
C.	must be more than cutoff frequency of TE₁₀ mode and less than cutoff frequency of TE₂₀ mode
D.	must be less than cutoff frequency of TE₁₀ mode
Answer» D. must be less than cutoff frequency of TE₁₀ mode

Discussion

27.	For a waveguide, which of the following statements is wrong?
A.	It is usually made of brass or aluminium
B.	It is usually rectangular or circular in shape
C.	The dielectric region is usually air
D.	The wall thickness is very small as compared to skin depth
Answer» E.

Discussion

28.	A line slightly longer than λ/4 length and short circuited at far end behaves as
A.	an inductance
B.	a capacitance
C.	L and C in series
D.	L and C in parallel
Answer» C. L and C in series

Discussion

29.	If a and b are the width and height of rectangular wave-guide the cut off wavelength λc for TE₂₀ mode is equal to
A.	a
B.	a + b
C.	a - b
D.	a² + b²
Answer» B. a + b

Discussion

30.	In π mode of operation of magnetron the spikes due to phase focussing effect rotate at an angular velocity corresponding to
A.	one pole/cycle
B.	two pole/cycle
C.	four pole/cycle
D.	six pole/cycle
Answer» C. four pole/cycle

Discussion

31.	Consider the following statements about a magic tee 1. The collinear arms are isolated from each other.2. On of the collinear arms is isolated from E arm.3. On of the collinear arms is isolated from H arm.4. E and H arms are isolated from each other. Of the above statements
A.	1 and 2 are correct
B.	1 and 3 are correct
C.	1 and 4 are correct
D.	2 and 3 are correct
Answer» D. 2 and 3 are correct

Discussion

32.	The condition of minimum distortion in a transmission line is
A.	RL = 1
B.	R = 0
C.	RG = L/C
D.	L = RC/G
Answer» E.

Discussion

33.	Assertion (A): Magnetron is generally used in n mode.Reason (R): Frequency for π mode can be easily separated from adjacent modes.
A.	Both A and R are correct and R is correct explanation of A
B.	Both A and R are correct but R is not correct explanation of A
C.	A is correct but R is wrong
D.	A is wrong but R is correct
Answer» B. Both A and R are correct but R is not correct explanation of A

Discussion

34.	A rectangular waveguide has width a. Then at the cutoff frequency (with corresponding wave length λc)
A.	a = λc/2
B.	a = λc
C.	a = λc/4
D.	a = 2λc
Answer» B. a = λc

Discussion

35.	A TE₁₀ rectangular waveguide is to be designed for operation over 25-35 GHz and the band centre is 1.5 times the cutoff frequency. The dimension of broadside is
A.	15 mm
B.	10 mm
C.	9 mm
D.	7.5 mm
Answer» E.

Discussion

36.	Characteristic impedance of a coaxial cable is inversely proportional to √∈r.
A.	True
B.	False
C.	May be True or False
D.	Can't say
Answer» B. False

Discussion

37.	In a circular waveguide TE₂₁ mode has lowest cutoff frequency
A.	True
B.	False
C.	May be True or False
D.	Can't say
Answer» C. May be True or False

Discussion

38.	For a 50 Ω resistor for 3 GHz application, the stray capacitance should be less than
A.	1 μF
B.	1 nF
C.	1 pF
D.	0.1 pF
Answer» E.

Discussion

39.	If 'a' is the width of rectangular wave guide and 'λ' is the wave length, then
A.	a > λ/4
B.	a > λ/2
C.	a < λ/4
D.	a < λ/2
Answer» C. a < λ/4

Discussion

40.	In TE₁₀ mode of rectangular waveguide
A.	there is one half sine wave variation along x direction and one along y direction
B.	there is one half sine wave variation along y direction and one along x direction
C.	there is one full sine wave variation along x direction and one along y direction
D.	none of the above
Answer» B. there is one half sine wave variation along y direction and one along x direction

Discussion

41.	Consider the following statements about instrument landing system of aircraft 1. It ensures correct landing under conditions of low visibility.2. It consists of runaway localizer, glide path equipment and marker beacons.3. It is basically a blind landing system. Which of above statements are correct?
A.	All
B.	1 and 2 only
C.	1 and 3 only
D.	2 only
Answer» B. 1 and 2 only

Discussion

42.	The transit time (in cycles) for electrons in repeller space of reflex klystron oscillator for sustaining oscillations is (n is any integer)
A.	2(n - 1)
B.	2n - 1
C.	n + 1/2
D.	n + 3/4
Answer» E.

Discussion

43.	Consider the following statements 1. Usable bandwidth of ridge wave guide is more than that of rectangular waveguide.2. For a given value of TM₁₀ cutoff frequency the cross section of ridge wave guide is lesser that that of rect angular waveguide.3. Ridge wave guide has higher conductor losser than a rectangular waveguide.4. Ridge guide has higher conductor losser than a rectangular waveguide. Which of the above statements are correct?
A.	1 and 2 only
B.	1, 2 and 3 only
C.	2 and 3 only
D.	All
Answer» C. 2 and 3 only

Discussion

44.	Assertion (A): A line of length λ/4 and short circuited at far end has an input impedance of infinity.Reason (R): A line of length λ/4 and short circuited at far end behaves as a parallel resonant circuit.
A.	Both A and R are correct and R is correct explanation of A
B.	Both A and R are correct but R is not correct explanation of A
C.	A is correct but R is wrong
D.	A is wrong but R is correct
Answer» B. Both A and R are correct but R is not correct explanation of A

Discussion

45.	The directivity in a receiving antenna1. increases the intercept area in forward direction2. reduces the noise picked up from other sources3. provides a means of discriminating against undesired signals originating in directions other than in which the desired transmitter lies. Which of the above statements are correct?
A.	1 only
B.	1 and 2 only
C.	1, 2 and 3
D.	2 and 3 only
Answer» D. 2 and 3 only

Discussion

46.	Consider the following statements about radar Beacon 1. It is also called transponder.2. It includes pulse transmitter, receiver and antenna.3. It replies with full power even when the signal receives is weak. Which of the above statements are correct?
A.	All
B.	1 and 2 only
C.	2 and 3 only
D.	2 only
Answer» B. 1 and 2 only

Discussion

47.	To ensure that only dominant mode TE₁₀ is allowed to propagate in an air filled rectangular waveguide, the lower frequency limit and upper frequency limit are
A.	about 25% above fc for TE₁₀ and 5% below fc for TE₂₀ mode respectively
B.	about 50% above fc for TE₁₀ and 25% below fc for TE₂₀ mode respectively
C.	about 25% above fc for TE₁₀ and 25% below fc for TE₂₀ mode respectively
D.	none of the above
Answer» B. about 50% above fc for TE₁₀ and 25% below fc for TE₂₀ mode respectively

Discussion

48.	In a microwave coaxial cable the inner conductor radius is a and inner radius of outside conductor is b. For TE₁₁ mode the cut off wavelength is about
A.	a + b
B.	π(a + b)
C.	πa
D.	πb
Answer» C. πa

Discussion

49.	Read the following statements about TWT 1. It uses thermionic emission.2. It uses an attenuater.3. It is inherently a resonant device.4. It has broad bandwidth. Which of the above are correct?
A.	1, 2, 3 and 4
B.	1, 2 and 3
C.	1, 3 and 4
D.	1, 2 and 4
Answer» E.

Discussion

50.	Consider the following statements 1. Gunn diode can be used in combinational logic circuits.2. Gunn diode can be used in sequential logic circuits.3. Both Gunn diode and GaAs Mesfet can be used in logic circuits. Which of the above statements are correct?
A.	1, 2, and 3
B.	1 and 2 only
C.	2 and 3 only
D.	1 and 3 only
Answer» B. 1 and 2 only

Discussion

Explore topic-wise MCQs in Electronics & Communication Engineering.

Characteristic impedance of a coaxial cable is inversely proportional to ∈r.

Assertion (A): In rectangular waveguide TE01 mode is just TE10 mode rotated by 90°.Reason (R): When a rectangular waveguide is rotated by 90°, the broad and narrow dimensions get interchanged.

Consider the following applications SwitchAttenuatorPhase shifterOscillator In which of the above can a PIN diode be used?

In the given figure the equivalent circuit of a T attenuator. If the condition for matched attenuator is

A microstrip line has ∈r = 9. The normalised wavelength is about

A circular waveguide carries TE11 mode whole radial electric field is given byEr = E0j1(r) sin Φ V/mwhere r is radial distance in cm from the axisThe cut off wavelength is

Guide wavelength (λg), cutoff wavelength (λc) and free space wavelength (λ0) of a waveguide are related as

If ZTE is wave impedance for TE waves, Ed is maximum dielectric strength of insulating material, a and b are the width and height of a rectangular wave guide, the maximum power handling capability Pmax for TE10 mode is

If a and b are the width and height of rectangular wave-guide the cut off wavelength λc for TE20 mode is equal to

For a rectangular waveguide having width a and height b, the cutoff wavelength for TM11 mode is equal to

If wavelength in free space is λ0 wavelength in insulator λ, μr is relative permittivity or insulator and ∈r is relative permittivity or insulator, then

If a line having Z0 = 300 ∠ 0 W is short circuited at far end, VSWR is

If a line having Z0 = 300 ∠ 0 W is open circuited at far end, VSWR is

If rv is reflection coefficient and VSWR is voltage standing wave ratio, then

The cavity resonator

Which of the following is used as a high power microwave oscillator?

A rectangular waveguide has two stubs each length λ/4 connected at the source end. The stubs are short circuted. Then

A line of length slightly less than λ/4 and short circuited at far end behaves as

Consider the following time parameters 1. Domain growth time constant.2. Transit time.3. Dielectric relaxation time in positive mobility regime. Which of the above are used in connection width transferred electron device?

Consider the following statements: 1. Impedance of Gunn diode is about tens of ohms.2. Impedance of Impatt diode is a few ohms.3. Impedance of Impatt diode are of the same order.4. Impedance of Impatt diode is more than that of Gunn diode. Which of the above statement are correct?

In a turnstile antenna two-half wave resonant wire radiators are placed at 90° to each other in the same plane and are excited

A line of characteristic impedance Z₀ branches into two line each with characteristic impedance Z₀. The refracted voltage is

What is the numerical aperture an optical fiber when critical angle is 30°?

Out of modes TE₂₀ and TE₃₀ of propagation of electromagnetic engery

A line of characteristic impedance 400 Ω is terminated by a resistance of 400 Ω. The reflected quantities are

To ensure that only dominant TE₁₀ mode propagates in a rectangular waveguide, the operating frequency

For a waveguide, which of the following statements is wrong?

A line slightly longer than λ/4 length and short circuited at far end behaves as

If a and b are the width and height of rectangular wave-guide the cut off wavelength λc for TE₂₀ mode is equal to

In π mode of operation of magnetron the spikes due to phase focussing effect rotate at an angular velocity corresponding to

Consider the following statements about a magic tee 1. The collinear arms are isolated from each other.2. On of the collinear arms is isolated from E arm.3. On of the collinear arms is isolated from H arm.4. E and H arms are isolated from each other. Of the above statements

The condition of minimum distortion in a transmission line is

Assertion (A): Magnetron is generally used in n mode.Reason (R): Frequency for π mode can be easily separated from adjacent modes.

A rectangular waveguide has width a. Then at the cutoff frequency (with corresponding wave length λc)

A TE₁₀ rectangular waveguide is to be designed for operation over 25-35 GHz and the band centre is 1.5 times the cutoff frequency. The dimension of broadside is

Characteristic impedance of a coaxial cable is inversely proportional to √∈r.

In a circular waveguide TE₂₁ mode has lowest cutoff frequency

For a 50 Ω resistor for 3 GHz application, the stray capacitance should be less than

If 'a' is the width of rectangular wave guide and 'λ' is the wave length, then

In TE₁₀ mode of rectangular waveguide

The transit time (in cycles) for electrons in repeller space of reflex klystron oscillator for sustaining oscillations is (n is any integer)

Assertion (A): A line of length λ/4 and short circuited at far end has an input impedance of infinity.Reason (R): A line of length λ/4 and short circuited at far end behaves as a parallel resonant circuit.

Consider the following statements about radar Beacon 1. It is also called transponder.2. It includes pulse transmitter, receiver and antenna.3. It replies with full power even when the signal receives is weak. Which of the above statements are correct?

To ensure that only dominant mode TE₁₀ is allowed to propagate in an air filled rectangular waveguide, the lower frequency limit and upper frequency limit are

In a microwave coaxial cable the inner conductor radius is a and inner radius of outside conductor is b. For TE₁₁ mode the cut off wavelength is about

Read the following statements about TWT 1. It uses thermionic emission.2. It uses an attenuater.3. It is inherently a resonant device.4. It has broad bandwidth. Which of the above are correct?

Consider the following statements 1. Gunn diode can be used in combinational logic circuits.2. Gunn diode can be used in sequential logic circuits.3. Both Gunn diode and GaAs Mesfet can be used in logic circuits. Which of the above statements are correct?