MCQOPTIONS
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MCQOPTIONS
This section includes 94 Mcqs, each offering curated multiple-choice questions to sharpen your Microwave Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
A ______ consists of a central thin conducting strip of width ω which is greater than its thickness t. It is placed inside the low loss dielectric (ϵr) substrate of thickness b/2 between two wide ground plates. The width of the ground plates is five time greater than the spacing between the plates. These are the planar transmission lines, used frequencies from 100MHz to 100GHz. |
| A. | micro strip line |
| B. | slot line |
| C. | parallel strip line |
| D. | strip line |
| Answer» E. | |
| 52. |
A lossless transmission line is terminated in a short circuit. The minimum possible length of the line for which it appears as a short circuit at its input terminals is |
| A. | λ/2 |
| B. | λ/4 |
| C. | λ |
| D. | 2λ |
| Answer» B. λ/4 | |
| 53. |
It is required to match a 200 Ω load to a 300 Ω transmission line to reduce the SWR along the line to 1. If it is connected directly to the load, the characteristic impedance of the quarter-wave transformer used for this purpose will be |
| A. | 275 Ω |
| B. | 260 Ω |
| C. | 245 Ω |
| D. | 230 Ω |
| Answer» D. 230 Ω | |
| 54. |
A 100V peak signal at 1 GHz is applied to a transmission line of characteristic impedance 100 Ω is terminated with an antenna of 75Ω. The peak values of reflected and incident currents are: |
| A. | 0.142 A, 1A |
| B. | 0.284 A, 1A |
| C. | 0.142 A, 2A |
| D. | 1A, 0.142 A |
| Answer» B. 0.284 A, 1A | |
| 55. |
An ideal lossless transmission line of Z0 60 Ω is connected to unknown ZL If SWR = 4. find ZL |
| A. | 240 Ω |
| B. | 480 Ω |
| C. | 120 Ω |
| D. | 100 Ω |
| Answer» B. 480 Ω | |
| 56. |
Given a range of frequencies, which of the following systems is best for transmission line load matching ? |
| A. | Single stub |
| B. | Double stub |
| C. | Single stub with adjustable position |
| D. | Quarter wave transformer |
| Answer» C. Single stub with adjustable position | |
| 57. |
For a perfectly matched line the reflection coefficient has value of: |
| A. | 0 |
| B. | 1 |
| C. | -1 |
| D. | Infinity |
| Answer» B. 1 | |
| 58. |
Inductance and capacitance per unit length of a lossless transmission line are 250 nH/m and 0.1 nF/m respectively. The velocity of the wave propagation and characteristic impedance of the transmission line are respectively |
| A. | 2 X 108 m/s, 100 Ω |
| B. | 3 X 108 m/s, 50 Ω |
| C. | 2 X 108 m/s, 50 Ω |
| D. | 3 X 108 m/s, 100 Ω |
| Answer» D. 3 X 108 m/s, 100 Ω | |
| 59. |
A transmission line having a characteristic impedance of 50 Ω is terminated at one end by j50 Ω. The voltage standing wave ratio produced will be |
| A. | ∞ |
| B. | +j |
| C. | 1 |
| D. | 0 |
| Answer» B. +j | |
| 60. |
At Ultra-high frequencies, short-circuited lossless transmission lines can be used to provide appropriate values of impedance. Match List I with List-II and select the correct answer using the code given below the lists:List IList IIa.l < λ / 41.Capacitiveb.λ / 4 < l < λ / 22.Inductivec.l = λ / 43.0d.L = λ / 24.∞ |
| A. | a-2, b-1, c-4, d-3 |
| B. | a-3, b-1, c-4, d-2 |
| C. | a-2, b-4, c-1, d-3 |
| D. | a-3, b-4, c-1, d-2 |
| Answer» B. a-3, b-1, c-4, d-2 | |
| 61. |
For a plane travelling EM wave, the correct equation for characteristic impedance Z for the medium with permittivity of ε and permeability of μ is: |
| A. | \(Z = \sqrt \frac {\mu}{\varepsilon}\) |
| B. | \(Z = \sqrt \frac {\varepsilon}{\mu}\) |
| C. | \(Z = \sqrt {(\mu * \varepsilon)}\) |
| D. | \(Z = \frac {1}{\sqrt {\mu*\varepsilon}}\) |
| Answer» B. \(Z = \sqrt \frac {\varepsilon}{\mu}\) | |
| 62. |
On a microstrip line, the wavelength measured is 12 mm for a 10 GHz signal. The dielectric constant of the equivalent homogeneous line is |
| A. | 3.5 |
| B. | 6.25 |
| C. | 5.5 |
| D. | 7 |
| Answer» C. 5.5 | |
| 63. |
A transmission line has a characteristic impedance of 500 Ω. It has been terminated in a 200 Ω load. If the load is dissipating a continuous power of 100 W, its reflection coefficient is |
| A. | \(\frac{6}{7}\) |
| B. | \(\frac{4}{7}\) |
| C. | \(\frac{3}{7}\) |
| D. | \(\frac{2}{7}\) |
| Answer» D. \(\frac{2}{7}\) | |
| 64. |
For energy propagation in a lossless transmission line, the characteristic impedance of the line is expressed in ohm as below (where notations have usual meanings). |
| A. | \(\sqrt{LC}\) Ω |
| B. | \(\sqrt{\frac{L}{C}}\) Ω |
| C. | \(\sqrt{\frac{C}{L}} \Omega \) |
| D. | \( \sqrt {\frac{{R\; + \;j\omega L}}{{G\; + \;j{\rm{\omega }}C}}}\) |
| Answer» C. \(\sqrt{\frac{C}{L}} \Omega \) | |
| 65. |
If a 75 Ω line is terminated by a load of (120 + j80) Ω, the maximum and minimum impedances over the line are nearly |
| A. | 135 Ω and 28 Ω |
| B. | 190.5 Ω and 28 Ω |
| C. | 135 Ω and 16 Ω |
| D. | 190.5 Ω and 16 Ω |
| Answer» C. 135 Ω and 16 Ω | |
| 66. |
Assertion (A): For transmission lines, having their length equal to odd multiples of \(\left( {\frac{\lambda }{4}} \right),\) the following expressions are given sin βL = ±1 and cos βL = 0.Reason (R): Under the above conditions, i.e. for odd multiples of Quarter wavelengths the input impedance becomes equal to \(Z = \frac{{{Z_0}.\cos h\left( {\alpha L} \right)}}{{\sin h\left( {\alpha L} \right)}}.\) |
| A. | Both (A) and (R) are true and (R) is the correct explanation of (A). |
| B. | Both (A) and (R) are 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» D. (A) is false, but (R) is true. | |
| 67. |
A measure of the mismatch between the maximum and minimum voltage and current variations along the transmission line is called SWR, i.e., standing wave ratio. SWR indicates how much power is delivered to the load, and how much is lost in the line. When SWR is 1, the percent reflected power is zero. When SWR is 1.5, the percent reflected power will be: |
| A. | 4 |
| B. | 8 |
| C. | 25 |
| D. | 40 |
| Answer» B. 8 | |
| 68. |
A transmission line of 50 Ω characteristic impedance terminated by a load impedance of 50 - 50j. The magnitude of reflection coefficient at the load is: |
| A. | √5 / 3 |
| B. | √3 / 5 |
| C. | 3√5 |
| D. | None of above |
| Answer» E. | |
| 69. |
A piece of coaxial cable has a 75 Ω characteristic impedance and a nominal capacitance of 69pF/m. What is the inductance per meter? |
| A. | 0.388 H/m |
| B. | 3.88 μH/m |
| C. | 38.8 μH/m |
| D. | 0.388 μH/m |
| Answer» E. | |
| 70. |
A quarter-wave transformer matching a 75 Ω source with a 300 Ω load should have a characteristic impedance of |
| A. | 50 Ω |
| B. | 100 Ω |
| C. | 150 Ω |
| D. | 200 Ω |
| Answer» D. 200 Ω | |
| 71. |
In a transmission line terminated by characteristic impedance, Z0 |
| A. | The reflection is maximum due to termination |
| B. | There are a large number of maximum and minimum on the line |
| C. | The incident current is zero for any applied signal |
| D. | There is no reflection of the incident wave |
| Answer» E. | |
| 72. |
A 75 Ω transmission line is first short-terminated and the minima locations are noted. When the short is replaced by a resistive load RL, the minima locations are not altered and the VSWR is measured to be 3. The value of RL is |
| A. | 25 Ω |
| B. | 50 Ω |
| C. | 225 Ω |
| D. | 250 Ω |
| Answer» B. 50 Ω | |
| 73. |
If a transmission line is terminated with a resistance equal to its characteristic impedance |
| A. | reflection coefficient will be unity |
| B. | standing wave ratio will be minimum |
| C. | the line loss will be maximum |
| D. | The input impedance will be twice the terminating resistance |
| Answer» C. the line loss will be maximum | |
| 74. |
A loss-less transmission line of length l is open-circuited and has characteristic impedance Z0. The input impedance is |
| A. | + j Z0 tan βl |
| B. | - j Z0 tan βl |
| C. | - j Z0 cot βl |
| D. | + j Z0 cot βl |
| Answer» D. + j Z0 cot βl | |
| 75. |
If the reflected wave at the load of a transmission line is 20 dB below the incident wave, the SWR at the load is: |
| A. | 1.5 |
| B. | 1.22 |
| C. | 3.0 |
| D. | 4.0 |
| Answer» C. 3.0 | |
| 76. |
A two-part network has the ABCD parameters \(\left[ {\begin{array}{*{20}{c}} 7&8\\ 3&4 \end{array}} \right]\). Two such identical networks are cascaded. The ABCD parameters of the overall cascaded network will be |
| A. | \(\left[ {\begin{array}{*{20}{c}} 14&16\\ 6&8 \end{array}} \right]\) |
| B. | \(\left[ {\begin{array}{*{20}{c}} 73&88\\ 33&40 \end{array}} \right]\) |
| C. | \(\left[ {\begin{array}{*{20}{c}} 1&1\\ 1&1 \end{array}} \right]\) |
| D. | \(\left[ {\begin{array}{*{20}{c}} 49&64\\ 9&16 \end{array}} \right]\) |
| Answer» C. \(\left[ {\begin{array}{*{20}{c}} 1&1\\ 1&1 \end{array}} \right]\) | |
| 77. |
In the following Smith Chart, Constant VSWR circlethe movement from y along a constant VSWR circle to y1 needs addition of |
| A. | Capacitance in series with y |
| B. | Capacitance in shunt with y |
| C. | TRL in series with y |
| D. | Stub with y |
| Answer» C. TRL in series with y | |
| 78. |
Consider a transmission line of characteristic impedance 50 Ω. Let it be terminated at one end by +j50 Ω. The VSWR produced by it in the transmission line will be |
| A. | 1 |
| B. | 0 |
| C. | Infinity |
| D. | +j |
| Answer» D. +j | |
| 79. |
A parallel plate lossless transmission line consists of brass strips of width w and separated by a distance d. If both w and d are doubled then its characteristic impedance will be |
| A. | halved |
| B. | doubled |
| C. | not change |
| D. | none of these |
| Answer» D. none of these | |
| 80. |
For a terminated uniform transmission line, the impedance Zx at a distance x from the load will be(a) \({Z_0}\frac{{{Z_L} + {Z_O}\tan hγ x}}{{{Z_O} + {Z_L}\tan hγ x}}{\rm{Ω }}\)(b) \({Z_L}\frac{{{Z_L} + {Z_O}\tan hγ x}}{{{Z_O} + {Z_L}\tan hγ x}}{\rm{Ω }}\)(c) \({Z_0}\frac{{{Z_L} + j{Z_O}\tan hγ x}}{{{Z_O} + j{Z_L}\tan hγ x}}{\rm{Ω }}\)(d) \({Z_L}\frac{{{Z_L} + j{Z_O}\tan hγ x}}{{{Z_O} + j{Z_L}\tan hγ x}}{\rm{Ω }}\)where:Z0 = Characteristic impedance of the line, ΩZL = Load impedance, Ωγ = Propagation constant = α + jβ, m-1α = Attenuation constant, Npm-1β = Phase constant, rad m-1 |
| A. | (a) |
| B. | (b) |
| C. | (c) |
| D. | (d) |
| Answer» B. (b) | |
| 81. |
A lossless microstrip transmission line consists of a trace of width |
| A. | \({Z_0} > \sqrt {\frac{{Lt}}{{{\varepsilon _0}{\varepsilon _r}w}}} \) |
| B. | \({Z_0} < \sqrt {\frac{{Lt}}{{{\varepsilon _0}{\varepsilon _r}w}}} \) |
| C. | \({Z_0} > \sqrt {\frac{{Lw}}{{{\varepsilon _0}{\varepsilon _r}t}}} \) |
| D. | \({Z_0} < \sqrt {\frac{{Lw}}{{{\varepsilon _0}{\varepsilon _r}t}}} \) |
| Answer» C. \({Z_0} > \sqrt {\frac{{Lw}}{{{\varepsilon _0}{\varepsilon _r}t}}} \) | |
| 82. |
A lossless matching circuit is shown in the figureThe values satisfying the matching condition are: |
| A. | XS1 = -j25.1, XP = +j100, XS2 = -j50 |
| B. | XS1 = +j25.1, XP = -j100, XS2 = -j50 |
| C. | XS1 = -j25.1, XP = -j100, XS2 = -j50 |
| D. | XS1 = +j25.1, XP = +j100, XS2 = +j100 |
| Answer» B. XS1 = +j25.1, XP = -j100, XS2 = -j50 | |
| 83. |
A TEM mode transmission line is having distributed circuit parameters as R = 1 ohm/m, L = 200 nH/m, G = 300 μS/m, C = 60 pF, the line is |
| A. | Loss-less |
| B. | Lossy |
| C. | Distortion-less |
| D. | None of the above |
| Answer» D. None of the above | |
| 84. |
A lossless transmission line is terminated by a short circuit such that it gives impedance of jZ0Ω at the input end. What is the length of line? |
| A. | \(\rm \frac{\lambda}{2}\) |
| B. | \(\rm \frac{\lambda}{4}\) |
| C. | \(\rm \frac{\lambda}{8}\) |
| D. | \(\lambda\) |
| Answer» D. \(\lambda\) | |
| 85. |
FOR_A_LOSSY_TRANSMISSION_LINE,_‚ÂÀ√≠‚ÄÖ√¢‚Ä¢=0.02+J0.15_AND_IS_20M_LONG._THE_LINE_IS_TERMINATED_WITH_AN_IMPEDANCE_OF_A_400‚ÂÀ√≠¬¨¬©._THEN_THE_INPUT_IMPEDANCE_OF_THE_TRANSMISSION_LINE_GIVEN_THAT_THE_CHARACTERISTIC_IMPEDANCE_OF_THE_TRANSMISSION_LINE_IS_156.13+J11.38‚ÂÀ√≠¬¨¬©_IS:?$# |
| A. | 100+j50 Ω |
| B. | 228+j36.8 Ω |
| C. | 50+36.8j Ω |
| D. | none of the mentioned |
| Answer» C. 50+36.8j ‚âà√≠¬¨¬© | |
| 86. |
FOR_A_DISTORTION_LESS_LINE,_R=_0.8‚ÂÀ√≠¬¨¬©/M,_G=_0.8_MSIEMENS/M,_L=_0.01¬¨¬®¬¨¬µH/M_THEN_C_IS:?$# |
| A. | 10 pF |
| B. | 1pF |
| C. | 1nF |
| D. | 10nF |
| Answer» B. 1pF | |
| 87. |
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 | |
| 88. |
A lossy line that has a linear phase factor as a function of frequency is called: |
| A. | distortion less line |
| B. | terminated lossy line |
| C. | loss less line |
| D. | lossy line |
| Answer» B. terminated lossy line | |
| 89. |
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 | |
| 90. |
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 | |
| 91. |
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. 100‚âà√≠¬¨¬© | |
| 92. |
Expression for characteristic impedance Z‚Çí of a transmission line in terms of L and C the transmission line is:$ |
| A. | ‚àö(C/L) |
| B. | ‚àö(CL) |
| C. | ‚àö(L/C) |
| D. | 1/‚àö(LC) |
| Answer» D. 1/‚Äö√Ñ√∂‚àö‚Ć‚àö‚àÇ(LC) | |
| 93. |
Expression for α(attenuation constant) in terms of R , G, L and C of a transmission line is:$ |
| A. | (R‚àö(C/L)+G‚àö(L/C))0.5 |
| B. | (R‚àö(C/L)+G‚àö(L/C)) |
| C. | (R‚àö(L/C)+G‚àö(C/L)) |
| D. | (R‚àö(L/C)+G‚àö(C/L))0.5 |
| Answer» B. (R‚Äö√Ñ√∂‚àö‚Ć‚àö‚àÇ(C/L)+G‚Äö√Ñ√∂‚àö‚Ć‚àö‚àÇ(L/C)) | |
| 94. |
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 > > ‚âà√¨‚àö¬¢L and G > >‚âà√¨‚àö¬¢C | |