In a coaxial transmission line, the useful power flows through

both inner and outer conductors

the interface of the two conductors

both inner and outer conductors

Any length of a transmission line may be made to appear as an infinitely long line by

leaving the line open at the end

increasing the standing wave ratio above unity

terminating the line in its characteristic impedance

For a line to have a purely resistive characteristic impedancewhere R and G are resistance and conductance per unit length respectively and L and C are inductance and capacitance per unit length respectively.

\(\omega L = \frac{1}{{\omega C}}\)

Characteristic impedance is given by ___________

\(Z_o^2 = \frac{1}{2}{Z_{SC}}.{Z_{OC}}\)

In the following figure, the transmitter Tx sends a wideband modulated RF signal via a coaxial cable to the receiver Rx. The output impedance ZT of Tx, the characteristic impedance Z0 of the cable, and the input impedance ZR of Rx are all real.Which one of the following statements is TRUE about the distortion of the received signal due to impedance mismatch?

Impedance mismatches do NOT result in signal distortion but reduce power transfer efficiency

The signal gets distorted if ZR ≠ Z0, irrespective of the value of ZT

The signal gets distorted if ZT ≠ Z0, irrespective of the value of ZR

Signal distortion implies impedance mismatch at both ends: ZT ≠ Z0 and ZR ≠ Z0

Impedance mismatches do NOT result in signal distortion but reduce power transfer efficiency

A lossless transmission line with characteristic impedance Z0 = 50 ohm is 30 m long and operates at 2 MHz. The line is shorted at the load, if the phase velocity = 0.6 times the velocity of light, the input impedance of the line is

\(\frac{{100}}{{\sqrt 2 }}\angle 180^\circ \;ohm\)

\(\frac{{75}}{{\sqrt 2 }}\angle 270^\circ \;ohm\)

If the RF transmission is terminated in its characteristic impedance Z0, which of the following statements is correct:

The input impedance of transmission line becomes Z0.

The transmission line acts as an infinite long transmission line.

Directions: The item consists of two statements, one labeled as the ‘Assertion (A)’ and the other as ‘Reason (R)’.You are to examine these two statements carefully and select the answers to the item using the codes given below:Assertion (A): The impedance of a matched load is equal to the characteristic impedance of the line.Reason (R): A matched termination absorbs the entire power incident on it.

Both A and R are individually true but R is not the correct explanation of A

Both A and R individually true and R is the correct explanation of A

Both A and R are individually true but R is not the correct explanation of A

94 + Mcqs in Lossy Transmission Lines in Microwave Engineering Page 1 McqOptions

1.	For a lossy transmission line, γ=0.02+j0.15 and is 20m long. The line is terminated with an impedance of a 400Ω. Then the input impedance of the transmission line given that the characteristic impedance of the transmission line is 156.13+j11.38Ω is:
A.	100+j50 Ω
B.	228+j36.8 Ω
C.	50+36.8j Ω
D.	none of the mentioned
Answer» C. 50+36.8j Ω

Discussion

2.	For a distortion less line, R= 0.8Ω/m, G= 0.8 msiemens/m, L= 0.01µH/m then C is:
A.	10 pF
B.	1pF
C.	1nF
D.	10nF
Answer» B. 1pF

Discussion

3.	The condition for a distortion less line is:
A.	R/L=G/C
B.	R/C=G/L
C.	R=G
D.	C=L
Answer» B. R/C=G/L

Discussion

4.	If R = 1.5Ω/m, G = 0.2 mseimens/m, L = 2.5 nH/m, C = 0.1 pF/m for a low loss transmission line, then the attenuation constant of the transmission line is:
A.	0.0.158
B.	0.0523
C.	0.0216
D.	0.0745
Answer» B. 0.0523

Discussion

5.	If the characteristic impedance of a transmission line is 50 Ω, and the inductance of the transmission line being 25 mH/m, the capacitance of the lossy transmission line is:
A.	1µF
B.	10 µF
C.	0.1 µF
D.	50 µF
Answer» C. 0.1 µF

Discussion

6.	If the inductance and capacitance of a loss line transmission line are 45 mH/m and10 µF/m, the characteristic impedance of the transmission line is:
A.	50Ω
B.	67.08Ω
C.	100Ω
D.	none of the mentioned
Answer» C. 100Ω

Discussion

7.	Expression for characteristic impedance Zₒ of a transmission line in terms of L and C the transmission line is:
A.	√(C/L)
B.	√(CL)
C.	√(L/C)
D.	1/√(LC)
Answer» D. 1/√(LC)

Discussion

8.	Expression for α(attenuation constant) in terms of R , G, L and C of a transmission line is:
A.	(R√(C/L)+G√(L/C))0.5
B.	(R√(C/L)+G√(L/C))
C.	(R√(L/C)+G√(C/L))
D.	(R√(L/C)+G√(C/L))0.5
Answer» B. (R√(C/L)+G√(L/C))

Discussion

9.	For a low loss line when both conductor and di-electric loss is small, the assumption that could be made is:
A.	R < < ωL and G < < ωC
B.	R > > ωL and G > >ωC
C.	R < <ωC and G < < ωL
D.	R > >ωC and G > >ωL
Answer» B. R > > ωL and G > >ωC

Discussion

10.	A long transmission line has considerable __________ effect
A.	series capacitance
B.	shunt capacitance
C.	series inductance
D.	shunt inductance
Answer» C. series inductance

Discussion

11.	For a two port network to be reciprocal, its Scattering parameters must satisfy the following condition, for i = 1,2 ; j = 1,2
A.	Sij = Sji (i ≠ j)
B.	Sij = Sji (i = j)
C.	Sij = 1/Sji (i ≠ j)
D.	Sij ≠ Sji (i = j)
Answer» B. Sij = Sji (i = j)

Discussion

12.	A quarter wavelength transformer is used as matching unit between two transmission lines of characteristics impedances 200Ω and 50Ω respectively. Find the characteristic impedance of transformer:
A.	150 Ω
B.	50 Ω
C.	200 Ω
D.	100 Ω
Answer» E.

Discussion

13.	Magic Tee is called as
A.	E-H plane Tee
B.	Hybrid Tee
C.	Mixer circuit
D.	All of the above
Answer» E.

Discussion

14.	A transmission line is terminated at its characteristic impedance. The reflection coefficient is
A.	1
B.	-1
C.	0
D.	∞
Answer» D. ∞

Discussion

15.	If L and C are inductance per unit length and capacitance per unit length of a lossless transmission line, then the velocity of propagation(v) on this line is given by
A.	v = √( L)/C
B.	v = 1 / √( LC)
C.	v = √(L/C)
D.	none of the above
Answer» C. v = √(L/C)

Discussion

16.	Consider the 3 m long lossless air-filled transmission line shown in the figure. It has a characteristic impedance of 120π Ω, is terminated by a short circuit, and is excited with a frequency of 37.5 MHz. What is the nature of the input impedance (Zin)?
A.	Open
B.	Short
C.	Inductive
D.	Capacitive
Answer» E.

Discussion

17.	Indicate the false statement. The SWR on a transmission line is infinity, the line is terminated in _________
A.	a short circuit
B.	a complex impedance
C.	an open circuit
D.	a pure resistance
Answer» E.

Discussion

18.	A quarter wave-length transformer is used to match a load of 200 Ω to a line with an input impedance of 50Ω. The characteristic impedance of the transformer would be
A.	40 Ω
B.	100 Ω
C.	400 Ω
D.	1000 Ω
Answer» C. 400 Ω

Discussion

19.	In a coaxial transmission line, the useful power flows through
A.	the interface of the two conductors
B.	both inner and outer conductors
C.	inner conducto
D.	outer conductor
Answer» B. both inner and outer conductors

Discussion

20.	Characteristic impedance of a quarter wave transformer connected in between a load of 100 ohm and a transmission line of characteristic impedance 225 ohms is
A.	100 ohm
B.	225 ohm
C.	600 ohm
D.	150 ohm
Answer» E.

Discussion

21.	For a lossless line terminated in a Short Circuit, the stationary voltage minima, and maxima are separated by
A.	λ/8
B.	λ/2
C.	λ/3
D.	λ/4
Answer» E.

Discussion

22.	A very lossy, λ/4 long, 50 ohm transmission line is open circuited at the load end. The input impedance measured at the other end of the line is approximately.
A.	0
B.	∞
C.	50 ohm
D.	none of the above
Answer» B. ∞

Discussion

23.	A purely resistance load ZL is connected to a 50 Ω lossless transmission line such that it has a voltage standing wave ratio of 3. The possible value of ZL will be -
A.	16.66 Ω
B.	450 Ω
C.	Both 1 & 2
D.	None of these
Answer» D. None of these

Discussion

24.	A transmission line with a characteristic impedance of 100 Ω is used to match a 50 Ω section to a 200 Ω section. If the matching is to be done both at 500 MHz and 1.2 GHz, the length of the transmission line can be approximately,
A.	1.75 m
B.	1.0 m
C.	1.35 m
D.	1.5 m
Answer» E.

Discussion

25.	A 50-ohm lossless line connects to a signal of 300 kHz to a load of 100 ohms. If load power is 50 mW, then the Voltage Standing Wave Ratio (VSWR) is:
A.	2
B.	0.5
C.	4
D.	1
Answer» B. 0.5

Discussion

26.	Consider the following statements in case of a magic Tee:1. The collinear arms are isolated from each other2. One of the collinear arms is isolated from E-arm3. One of the collinear arms is isolated from H-arm4. E and H arms are isolated from each otherWhich of these statements are correct?
A.	1 and 2
B.	2 and 3
C.	3 and 4
D.	1 and 4
Answer» E.

Discussion

27.	Any length of a transmission line may be made to appear as an infinitely long line by
A.	leaving the line open at the end
B.	increasing the standing wave ratio above unity
C.	shorting the line at the end
D.	terminating the line in its characteristic impedance
Answer» E.

Discussion

28.	A lossless transmission line has Z0 = 100 Ω, terminated by an unknown impedance. The termination is found to be at a maximum of the voltage standing wave, and the Voltage Standing Wave Ratio (VSWR) is 5. The value of the terminating impedance is:
A.	500
B.	50
C.	20
D.	0.05
Answer» B. 50

Discussion

29.	Consider the following statements regarding a transmission line:1. Its attenuation is constant and is independent of frequency.2. Its attenuation varies linearly with frequency.3. Its phase shift varies linearly with frequency.4. Its phase shift is constant and is independent of frequency.Which of the above statements are correct for distortionless line?
A.	1, 2, 3 and 4
B.	2 and 3 only
C.	1 and 3 only
D.	3 and 4 only
Answer» D. 3 and 4 only

Discussion

30.	Consider the following statements about the smith chart:1. A complete revolution (360°) around the Smith that represent a distance of half wavelength on the line.2. Clockwise movement on the chart is regarded as moving toward the generator.3. Although three scales around the periphery of Smith chart are used, but only one scale can be sufficent.4. Sumit chart cannot be used as admittance chart.Which of these statements are correct?
A.	1, 2, 3 and 4
B.	1, 2 and 4 only
C.	2, 3 and 4 only
D.	1, 2 and 3 only
Answer» E.

Discussion

31.	For a line to have a purely resistive characteristic impedancewhere R and G are resistance and conductance per unit length respectively and L and C are inductance and capacitance per unit length respectively.
A.	\(\frac{C}{G} = \frac{R}{L}\)
B.	\(\omega L = \frac{1}{{\omega C}}\)
C.	R = G
D.	GL = RC
Answer» E.

Discussion

32.	A transmission line having 50 Ω impedance is terminated in a load of (40 + j30) Ω. The VSWR is
A.	1.333
B.	0.8
C.	1
D.	2
Answer» E.

Discussion

33.	Input reflection coefficient ‘S11’ of the 2-port network for 50 Ω system is:
A.	1/3 ∠0°
B.	1/2 ∠180°
C.	1/3 ∠180°
D.	1/2 ∠0°
Answer» D. 1/2 ∠0°

Discussion

34.	Characteristic impedance is given by ___________
A.	\(Z_o^2 = 2{Z_{SC}}.{Z_{OC}}\)
B.	\(Z_o^2 = \frac{1}{2}{Z_{SC}}.{Z_{OC}}\)
C.	\(Z_o^2 = {Z_{SC}}.{Z_{OC}}\)
D.	\(Z_o^2 = 4{Z_{SC}}.{Z_{OC}}\)
Answer» D. \(Z_o^2 = 4{Z_{SC}}.{Z_{OC}}\)

Discussion

35.	In the following figure, the transmitter Tx sends a wideband modulated RF signal via a coaxial cable to the receiver Rx. The output impedance ZT of Tx, the characteristic impedance Z0 of the cable, and the input impedance ZR of Rx are all real.Which one of the following statements is TRUE about the distortion of the received signal due to impedance mismatch?
A.	The signal gets distorted if ZR ≠ Z0, irrespective of the value of ZT
B.	The signal gets distorted if ZT ≠ Z0, irrespective of the value of ZR
C.	Signal distortion implies impedance mismatch at both ends: ZT ≠ Z0 and ZR ≠ Z0
D.	Impedance mismatches do NOT result in signal distortion but reduce power transfer efficiency
Answer» D. Impedance mismatches do NOT result in signal distortion but reduce power transfer efficiency

Discussion

36.	Consider the following statements:As compared to short-circuited stubs, the open-circuited stubs are not preferred because the latter1. Are of different characteristic impedance2. Have a tendency to radiateWhich of the above statements is/are correct?
A.	1 only
B.	2 only
C.	Both 1 and 2
D.	Neither 1 nor 2
Answer» C. Both 1 and 2

Discussion

37.	A line of characteristic impedance 50 ohms is terminated at one end by +j50 ohms. The VSWR on the line is
A.	1
B.	∞
C.	0
D.	j
Answer» C. 0

Discussion

38.	A microstrip line with alumina substrate εr = 9 has a strip width w = 3 mm. Substrate thickness h = 0.5 mm.What is the approximate characteristic impedance of the line, assuming TEM wave propagation and negligible fringing field?
A.	50 Ω
B.	26 Ω
C.	21 Ω
D.	10 Ω
Answer» D. 10 Ω

Discussion

39.	A____ consist of an inner conductor with inner diameter d, and then a concentric cylindrical insulating material around it. This is surrounded by an outer conductor, which is a concentric cylinder with an inner diameter of D. This is mostly used for high-frequency applications. This structure is well understood by taking a look at the given figure.
A.	Slot line
B.	Co-axial line
C.	Microstrip line
D.	Strip line
Answer» C. Microstrip line

Discussion

40.	A quarter-wave transformer of characteristic impedance 60 Ω has been used to match a transmission line of characteristic impedance Z0 with a load of 72 Ω. What is the characteristic impedance of the transformer, when the load of 72 Ω is replaced by 98 Ω?
A.	98 Ω
B.	80 Ω
C.	70 Ω
D.	60 Ω
Answer» D. 60 Ω

Discussion

41.	Conditions for a transmission line to be of low loss are
A.	R >> ωL, G ωC
B.	R ≪ ωL, G ωC
C.	R ≪ ωL, G ≪ ωC
D.	R ωL, G ≪ ωC
Answer» D. R ωL, G ≪ ωC

Discussion

42.	Find the velocity of propagation for a transmission line having the following parameters.R = 84 Ω/Km, G = 10-6 mho/Km, L = 0.01 Henry/Km, C = 0.061 μF/Km and frequency = 1000 Hz
A.	34.9 × 10-6 m/sec
B.	42.6 × 10-6 m/sec
C.	56.7 × 10-6 m/sec
D.	14.9 × 10-6 m/sec
Answer» C. 56.7 × 10-6 m/sec

Discussion

43.	A lossless transmission line with characteristic impedance Z0 = 50 ohm is 30 m long and operates at 2 MHz. The line is shorted at the load, if the phase velocity = 0.6 times the velocity of light, the input impedance of the line is
A.	75∠90° ohm
B.	153.85∠ 90°
C.	\(\frac{{100}}{{\sqrt 2 }}\angle 180^\circ \;ohm\)
D.	\(\frac{{75}}{{\sqrt 2 }}\angle 270^\circ \;ohm\)
Answer» C. \(\frac{{100}}{{\sqrt 2 }}\angle 180^\circ \;ohm\)

Discussion

44.	If the RF transmission is terminated in its characteristic impedance Z0, which of the following statements is correct:
A.	The input impedance of transmission line becomes Z0.
B.	The transmission line acts as an infinite long transmission line.
C.	The VSWR becomes one
D.	The VSWR becomes infinite.
Answer» D. The VSWR becomes infinite.

Discussion

45.	An elliptically polarized wave travelling in the position Z-direction in air has x and y componentsEX = 3 sin (ωt - βz) V/mEY = 6 sin (ωt - βz + 75°) V/mIf the characteristic impedance of air is 360 Ω, the average power per unit area conveyed by the wave is
A.	8 W/m2
B.	4 W/m2
C.	62⋅5 mW/m2
D.	125 mW/m2
Answer» D. 125 mW/m2

Discussion

46.	Directions: The item consists of two statements, one labeled as the ‘Assertion (A)’ and the other as ‘Reason (R)’.You are to examine these two statements carefully and select the answers to the item using the codes given below:Assertion (A): The impedance of a matched load is equal to the characteristic impedance of the line.Reason (R): A matched termination absorbs the entire power incident on it.
A.	Both A and R individually true and R is the correct explanation of A
B.	Both A and R are individually true but R is not the correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» B. Both A and R are individually true but R is not the correct explanation of A

Discussion

47.	A quarter-wave transformer is used for matching a load of 225 Ω connected to a transmission line of 256 Ω in order to reduce the SWR along the line to 1. The characteristic impedance of the transformer is
A.	225 Ω
B.	256 Ω
C.	240 Ω
D.	273 Ω
Answer» D. 273 Ω

Discussion

48.	A λ/4 line, shorted at one end presents impedance at the other end equal to
A.	Z0
B.	√ 2 Z0
C.	∞
D.	0
Answer» D. 0

Discussion

49.	For a parallel RC circuit as shown in figure, R = 20 Ω & C = 0.9 pF, which is to be matched to 50 Ω over a bandwidth,\(\int^{\infty}_0 \ln \frac {1}{\|Γ\|} dw \le \frac {\pi}{R\; C}\)The circuit has to be matched over 6 GHz to 18 GHz. What is the very best Γ that can be achieved:
A.	0
B.	0.05
C.	0.1
D.	1
Answer» D. 1

Discussion

50.	Ideally Voltage Standing Wave Ratio (VSWR) should be
A.	As large as possible
B.	As small as possible
C.	As close to unity as possible
D.	Infinity
Answer» D. Infinity

Discussion

Explore topic-wise MCQs in Microwave Engineering.

For a lossy transmission line, γ=0.02+j0.15 and is 20m long. The line is terminated with an impedance of a 400Ω. Then the input impedance of the transmission line given that the characteristic impedance of the transmission line is 156.13+j11.38Ω is:

For a distortion less line, R= 0.8Ω/m, G= 0.8 msiemens/m, L= 0.01µH/m then C is:

The condition for a distortion less line is:

If R = 1.5Ω/m, G = 0.2 mseimens/m, L = 2.5 nH/m, C = 0.1 pF/m for a low loss transmission line, then the attenuation constant of the transmission line is:

If the characteristic impedance of a transmission line is 50 Ω, and the inductance of the transmission line being 25 mH/m, the capacitance of the lossy transmission line is:

If the inductance and capacitance of a loss line transmission line are 45 mH/m and10 µF/m, the characteristic impedance of the transmission line is:

Expression for characteristic impedance Zₒ of a transmission line in terms of L and C the transmission line is:

Expression for α(attenuation constant) in terms of R , G, L and C of a transmission line is:

For a low loss line when both conductor and di-electric loss is small, the assumption that could be made is:

A long transmission line has considerable __________ effect

For a two port network to be reciprocal, its Scattering parameters must satisfy the following condition, for i = 1,2 ; j = 1,2

A quarter wavelength transformer is used as matching unit between two transmission lines of characteristics impedances 200Ω and 50Ω respectively. Find the characteristic impedance of transformer:

Magic Tee is called as

A transmission line is terminated at its characteristic impedance. The reflection coefficient is

If L and C are inductance per unit length and capacitance per unit length of a lossless transmission line, then the velocity of propagation(v) on this line is given by

Consider the 3 m long lossless air-filled transmission line shown in the figure. It has a characteristic impedance of 120π Ω, is terminated by a short circuit, and is excited with a frequency of 37.5 MHz. What is the nature of the input impedance (Zin)?

Indicate the false statement. The SWR on a transmission line is infinity, the line is terminated in _________

A quarter wave-length transformer is used to match a load of 200 Ω to a line with an input impedance of 50Ω. The characteristic impedance of the transformer would be

In a coaxial transmission line, the useful power flows through

Characteristic impedance of a quarter wave transformer connected in between a load of 100 ohm and a transmission line of characteristic impedance 225 ohms is

For a lossless line terminated in a Short Circuit, the stationary voltage minima, and maxima are separated by

A very lossy, λ/4 long, 50 ohm transmission line is open circuited at the load end. The input impedance measured at the other end of the line is approximately.

A purely resistance load ZL is connected to a 50 Ω lossless transmission line such that it has a voltage standing wave ratio of 3. The possible value of ZL will be -

A transmission line with a characteristic impedance of 100 Ω is used to match a 50 Ω section to a 200 Ω section. If the matching is to be done both at 500 MHz and 1.2 GHz, the length of the transmission line can be approximately,

A 50-ohm lossless line connects to a signal of 300 kHz to a load of 100 ohms. If load power is 50 mW, then the Voltage Standing Wave Ratio (VSWR) is:

Consider the following statements in case of a magic Tee:1. The collinear arms are isolated from each other2. One of the collinear arms is isolated from E-arm3. One of the collinear arms is isolated from H-arm4. E and H arms are isolated from each otherWhich of these statements are correct?

Any length of a transmission line may be made to appear as an infinitely long line by

A lossless transmission line has Z0 = 100 Ω, terminated by an unknown impedance. The termination is found to be at a maximum of the voltage standing wave, and the Voltage Standing Wave Ratio (VSWR) is 5. The value of the terminating impedance is:

For a line to have a purely resistive characteristic impedancewhere R and G are resistance and conductance per unit length respectively and L and C are inductance and capacitance per unit length respectively.

A transmission line having 50 Ω impedance is terminated in a load of (40 + j30) Ω. The VSWR is

Input reflection coefficient ‘S11’ of the 2-port network for 50 Ω system is:

Characteristic impedance is given by ___________

Consider the following statements:As compared to short-circuited stubs, the open-circuited stubs are not preferred because the latter1. Are of different characteristic impedance2. Have a tendency to radiateWhich of the above statements is/are correct?

A line of characteristic impedance 50 ohms is terminated at one end by +j50 ohms. The VSWR on the line is

A microstrip line with alumina substrate εr = 9 has a strip width w = 3 mm. Substrate thickness h = 0.5 mm.What is the approximate characteristic impedance of the line, assuming TEM wave propagation and negligible fringing field?

A quarter-wave transformer of characteristic impedance 60 Ω has been used to match a transmission line of characteristic impedance Z0 with a load of 72 Ω. What is the characteristic impedance of the transformer, when the load of 72 Ω is replaced by 98 Ω?

Conditions for a transmission line to be of low loss are

Find the velocity of propagation for a transmission line having the following parameters.R = 84 Ω/Km, G = 10-6 mho/Km, L = 0.01 Henry/Km, C = 0.061 μF/Km and frequency = 1000 Hz

A lossless transmission line with characteristic impedance Z0 = 50 ohm is 30 m long and operates at 2 MHz. The line is shorted at the load, if the phase velocity = 0.6 times the velocity of light, the input impedance of the line is

If the RF transmission is terminated in its characteristic impedance Z0, which of the following statements is correct:

An elliptically polarized wave travelling in the position Z-direction in air has x and y componentsEX = 3 sin (ωt - βz) V/mEY = 6 sin (ωt - βz + 75°) V/mIf the characteristic impedance of air is 360 Ω, the average power per unit area conveyed by the wave is

A quarter-wave transformer is used for matching a load of 225 Ω connected to a transmission line of 256 Ω in order to reduce the SWR along the line to 1. The characteristic impedance of the transformer is

A λ/4 line, shorted at one end presents impedance at the other end equal to

For a parallel RC circuit as shown in figure, R = 20 Ω & C = 0.9 pF, which is to be matched to 50 Ω over a bandwidth,\(\int^{\infty}_0 \ln \frac {1}{|Γ|} dw \le \frac {\pi}{R\; C}\)The circuit has to be matched over 6 GHz to 18 GHz. What is the very best Γ that can be achieved:

Ideally Voltage Standing Wave Ratio (VSWR) should be