Microwave Engineering MCQs – Microwave Network Analysis MCQs ( Microwave Engineering ) MCQs
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Microwave Engineering MCQs – Microwave Network Analysis MCQs ( Microwave Engineering ) MCQs
The most occurred mcqs of Microwave Network Analysis MCQs ( Microwave Engineering ) in past papers. Past papers of Microwave Network Analysis MCQs ( Microwave Engineering ) Mcqs. Past papers of Microwave Network Analysis MCQs ( Microwave Engineering ) Mcqs . Mcqs are the necessary part of any competitive / job related exams. The Mcqs having specific numbers in any written test. It is therefore everyone have to learn / remember the related Microwave Network Analysis MCQs ( Microwave Engineering ) Mcqs. The Important series of Microwave Network Analysis MCQs ( Microwave Engineering ) Mcqs are given below:
Impedance and Admittance Matrices
1. The one below among others is not a type TEM line used in microwave networks:
a) Co-axial wire
b) Micro strip line
c) Strip lines
d) Surface guide
Answer: d
Explanation: Coaxial micro strip and strip lines all support TEM mode of propagation through them. But surface guides do not support TEM mode of propagation in them. Hence it cannot be called a TEM line.
2. The one below is the only micro wave network element that is a TEM line:
a) Co-axial cable
b) Rectangular wave guide
c) Circular wave guide
d) Surface wave guide
Answer: a
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.
3. The relation between voltage, current and impedance matrices of a microwave network is:
a) [V] = [Z][I].
b) [Z] = [V][I].
c) [I] = [Z][V].
d) [V] = [Z]-[I].
Answer: a
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.
4. The relation between voltage, current and admittance matrices of a microwave network is:
a) [I] = [Y] [V].
b) [Y] = [V] [I].
c) [I] = [Z] [V].
d) [V] = [Z]-1[I].
Answer: a
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.
5. Admittance and impedance matrices of a micro waves network are related as:
a) [Y] = [Z]-1.
b) [Y] = [Z].
c) [V] = [Z] [Z]-1.
d) [Z] = [V] [V]-1.
Answer: a
Explanation: Both admittance and impedance matrix can be defined for a microwave network. The relation between these admittance and impedance matrix is [Y] = [Z]-1. Admittance matrix is the inverse of the impedance matrix.
6. The element of a Z matrix, Zij can be given in terms of voltage and current of a microwave network as:
a) ZIJ = VI/IJ
b) ZIJ = VIIJ
c) 1//ZIJ = 1/JIVI
d) VIJ = IJ/JI
Answer: a
Explanation: The element Zij of a Z matrix is defined as the ratio of voltage at the ith port to the current at the jth port given that all other currents are set to zero.
7. In a two port network, if current at port 2 is 2A and voltage at port 1 is 4V, then the impedance Z₁₂ is:
a) 2 Ω
b) 8 Ω
c) 0.5 Ω
d) Insufficient data
Answer: a
Explanation: Z12 is defined as the ratio of the voltage at port 1 to the current at port 2. Substituting the given values in the above equation, Z12 parameter of the network is 2 Ω.
8. In a 2 port network, if current at port 2 is 2A and voltage at port 1 is 4 V, then the admittance Y₂₁ is:
a) 0.5 Ʊ
b) 8 Ʊ
c) 2 Ʊ
d) 4 Ʊ
Answer: a
Explanation: Admittance parameter Y12 is defined as the ratio of current at port 1 to the voltage at port 2. Taking the ratio, the admittance Y12 is 0.5 Ʊ.
9. For a reciprocal network, Z matrix is:
a) A unit matrix
b) Null matrix
c) Skew symmetric matrix
d) Symmetric matrix
Answer: d
Explanation: For a reciprocal matrix, the impedance measured at port Zij is equal to the impedance measured at port Zji. Since these parameters occupy symmetric positions in the Z matrix, the matrix becomes symmetric.
10. For a lossless network, the impedance and admittance matrices are:
a) Real
b) Purely imaginary
c) Complex
d) Rational
Answer: b
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.
11. The matrix with impedance parameters Z₁₁=1+j, Z₁₂=4+j, Z₂₂=1, Z21=4+j is said to be
a) Reciprocal network
b) Lossless network
c) Lossy network
d) None of the mentioned
Answer: a
Explanation: In the given case, Z12=Z21. This condition can be satisfied only by reciprocal networks. Hence the given network is a reciprocal network.
Scattering Matrices
1. S parameters are expressed as a ratio of:
a) Voltage and current
b) Impedance at different ports
c) Indecent and the reflected voltage waves
d) None of the mentioned
Answer: c
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.
2. The relation between incident voltage matrix , reflected voltage matrix and S matrix for a microwave network:
a) [v-] = [s] [v+].
b) [v+] = [s] [v-].
c) [v-] [v] = [s].
d) [s] = [v] [v-].
Answer: a
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.
3. The specific element Sij of the scattering matrix can be determined as:
a) SIJ= Vi-/Vj+
b) SIJ= Vi+/Vj-
c) S= Vj+/Vi-
d) None of the mentioned
Answer: a
Explanation: The parameter Sij is found by driving port j with an incident wave of voltage Vj+ coming out of ports i. The incident waves on all ports except the jth port are set to zero.
4. The device used to get the measurement of S parameters of n- port micro wave network is:
a) CRO
b) Network analyzer
c) Circulator
d) Attenuator
Answer: b
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.
5. For a one port network , the scattering parameter S₁₁ in terms of impedance parameter Z₁₁ is:
a) (Z11-1)/ (Z11+1)
b) (Z11+1)/ (Z11-1)
c) (Z11+1) (Z11-1)
d) Z11
Answer: a
Explanation: If Z matrix of a one port network is computed, then the s matrix of the same can be computed using the Z11 coefficient. To compute the S11 parameter of the network, the relation used is (Z11-1)/ (Z11+1).
6. Scattering matrix for a reciprocal network is:
a) Symmetric
b) Unitary
c) Skew symmetric
d) Identity matrix
Answer: a
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.
7. S₁₂=0.85-45⁰ and S₁₂=0.85 +45⁰ for a two port network. Then the two port network is:
a) Non-reciprocal
b) Lossless
c) Reciprocal
d) Lossy
Answer: a
Explanation: For a reciprocal network, the S matrix is symmetric. For the matrix to be symmetric, Sij=Sji. Since this condition is not satisfied in the above case, the matrix is non reciprocal.
8. Scattering matrix for a lossless matrix is:
a) Unitary
b) Symmetric
c) Identity matrix
d) Null matrix
Answer: a
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.
9. If the reflection co efficient of a 2 port network is 0.5 then the return network loss in the network is:
a) 6.5 dB
b) 0.15 dB
c) 6.020 dB
d) 10 dB
Answer: c
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.
10. If the reflection co efficient of a 2 port network is 0.25 then the return network loss in the network is:
a) 12.05 dB
b) 0.15 dB
c) 20 dB
d) 10 dB
Answer: a
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.
Transmission Matrix(ABCD)
1. ABCD matrix is used:
a) When there is two or more port networks in the cascade
b) To represent a 2 port network
c) To represent a 2 port network
d) To represent the impedance of a microwave network
Answer: a
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.
2. The voltage equation for a 2 port network that can be represented as a matrix is:
a) V1=AV2 + BI2
b) V1=CV2 + DI2
c) V1=BV2 +AI2
d) V1=DV2+CI2
Answer: a
Explanation: In the equation, V1 is the voltage measured at port 1 and V2 is the voltage measured at port 2 and I2 is the current measured at the second port. A and B are the network constants.
3. ABCD matrix of the cascade connection of 2 networks is equal to:
a) Product of ABCD matrices representing the individual two ports
b) Sum of the ABCD matrices representing the individual two ports
c) Difference of the ABCD matrices representing the individual two ports
d) Sum of transpose of ABCD matrices representing the individual two ports
Answer: a
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.
4. For simple impedance Z, the ABCD parameters are:
a) A=1, Z=B, C=0, D=1
b) A=0, B=1, C=1, D=0
c) A=Z, B=1, C=1, D=0
d) A=1, B=0, C=Z, D=1
Answer: a
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.
5. For a simple admittance Y, the ABCD parameters are:
a) A=1, B=0, C=Y, D=1
b) A=Z, B=1, C=1, D=0
c) A=1, B=0, C=Z, D=1
d) A=1, Y=B, C=0, D=1
Answer: a
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.
6. C parameter for a transmission line of characteristic impedance Zₒ, phase constant β and length ‘l’ is:
a) j Yₒ Sin βl
b) j Zₒ Sin βl
c) j Zₒ tan βl
d) j Yₒ tan βl
Answer: a
Explanation: If a transmission line is represented as two port network, constants can be derived in terms of the A, B, C, D constants for the network. But setting each electrical parameter to zero, this constant is found. By doing so, the C parameter of transmission line is j Yₒ Sin βl.
7. For a 2 port network if Z₁₁=1.5 and Z₁₂=1.2, A parameter for the same 2 port network is:
a) 1.5
b) 1.25
c) 0.75
d) 1.75
Answer: b
Explanation: A parameter for the two port network is the ratio of the impedance Z11 and the impedance Z12. Substituting in this equation,’ A’ parameter of the network is 1.25.
8. For a 2 port network, if the admittance parameter Y₁₂=0.4, then B among the ABCD, parameters for the 2 port network is:
a) 2.5
b) 4.5
c) 5
d) 6
Answer: a
Explanation: 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.
9. If D=1.6 and B=2.8 for a 2 port network, then Y₁₁=?
a) 0.5714
b) 0.987
c) 0.786
d) 1.75
Answer: a
Explanation: The admittance Y11 of the network is defined as the ratio of B parameter to the D parameter of the network. Taking the ratio of the given values, admittance Y11 is 0.5714.
10. If A=2.8 and B=1.4 for a 2 port network then Z₁₁=?
a) 0.5
b) 2
c) 4.2
d) 2.7
Answer: b
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.
Aperture Coupling
1. The matched network is placed between:
a) load and transmission line
b) source and the transmission line
c) source and the load
d) none of the mentioned
Answer: A
Explanation: At microwave frequencies, for maximum power transmission, the characteristic impedance of the transmission line must be matched to the load impedance with which the line is terminated. Hence to match these impedances, the matched network is laced between load and transmission line.
2. When a transmission line is matched to a load using a matched network, reflected waves are present:
a) between the load and the matched network
b) between the matched network and the transmission line
c) between the source and the transmission line
d) between the matched network and source
Answer: A
Explanation: The matching circuit is used to match the transmission line and the load. This circuit prevents the reflection of the waves reaching the source. Hence, reflected waves are present between the load and the matched network.
3. Impedance matching sensitive receiver components may improve the _____ of the system.
a) noise
b) SNR
c) amplification factor
d) thermal noise
Answer: B
Explanation: SNR (signal to noise ratio) of the system defines the ratio of signal power to noise power. An increase in this value results in increase of the signal strength. Impedance matching certain sensitive receiver components helps in delivering maximum power to the load and increased signal strength.
4. One of the most important factors to be considered in the selection of a particular matching network is:
a) noise component
b) amplification factor
c) bandwidth
d) none of the mentioned
Answer: C
Explanation: Any type of matching network can ideally give a perfect match at a single frequency. But it is desirable to match a load over a band of frequencies. Hence, bandwidth plays an important role in the selection of the matching network.
5. The simplest type of matching network, L section consists of _______ reactive elements.
a) one
b) two
c) four
d) six
Answer: B
Explanation: As the name of the matching circuit indicates, ‘L’ section consists of 2 reactive elements, one element vertical and another horizontal. 2 types of ‘L’ sections exist. The best one is chose based on the normalized value of the load impedance.
6. The major limitation of a lumped elements matching ‘L’ network is:
a) they are not equally efficient at higher frequencies as they are at lower frequencies.
b) size of the network
c) they restrict flow of current
d) none of the mentioned
Answer: A
Explanation: Since we use lumped elements like inductors and capacitors as the components of the matching network, they behave differently at frequencies higher than 1GHz, because of the frequency dependent factor of inductive and capacitive reactance. This is one of the major limitations.
7. An ‘L’ network is required to match a load impedance of 40Ω to a transmission line of characteristic impedance 60Ω. The components of the L network are:
a) 28.28+j0 Ω
b) 28.28+j1 Ω
c) 50Ω
d) 48.9Ω
Answer: A
Explanation: Since both load impedance and characteristic impedance are resistive (real), the imaginary part of the matching network is 0. Real part of the matching network is given by the expression ±√(RL(Z0– RL))-XL. Substituting the values given, the matching network impedance is 28.28Ω.
8. The imaginary part of the matching network is given by the relation:
a) ±(√(Z0– RL)/RL)Z00
b) ±(√(Z0– RL)/RL)
c) ±(√(Z0– RL)/ Z0
d) None of the mentioned
Answer: A
Explanation: By theoretical analysis, the expressions for real and imaginary parts of the impedance of the matching network are derived in terms of the load impedance and the characteristic impedance of the transmission line. This expression derived is ±(√(Z0– RL)/RL)Z0 .
9. Which of the following material is not used in the fabrication of resistors of thin films?
a) nichrome
b) tantalum nitride
c) doped semiconductor
d) pure silicon
Answer: D
Explanation: Certain physical properties are to be met in order to use a material to make thin film resistors. These properties are not found in pure silicon which is an intrinsic semiconductor.
10. Large values of inductance can be realized by:
a) loop of transmission line
b) spiral inductor
c) coils of wires
d) none of the mentioned
Answer: B
Explanation: Loop of transmission lines are used to make inductors to realize lower values of inductance. Coils of wires cannot be used to realize inductors at higher frequencies. Spiral conductors can be used to realize inductors of higher values at higher frequencies.
11. A short transmission line stub can be used to provide a shunt capacitance of:
a) 0-0.1µF
b) 0-0.1pF
c) 0-0.1nF
d) 1-10pF
Answer: B
Explanation: Since a transmission line consists of two wires, which can act plates of a capacitor, they can be used as a capacitor of very low values of the range 0-0.1pF.