# Microwave Engineering Questions and Answers – Scattering Matrices

This set of Microwave Engineering Multiple Choice Questions & Answers (MCQs) focuses on “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
View Answer

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-].
View Answer

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
View Answer

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.
advertisement
advertisement

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
View Answer

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
View Answer

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
View Answer

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
View Answer

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.
advertisement

8. Scattering matrix for a lossless matrix is:
a) Unitary
b) Symmetric
c) Identity matrix
d) Null matrix
View Answer

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
View Answer

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.
advertisement

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
View Answer

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.

Sanfoundry Global Education & Learning Series – Microwave Engineering.
To practice all areas of Microwave Engineering, here is complete set of 1000+ Multiple Choice Questions and Answers.

If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]

advertisement
advertisement
Subscribe to our Newsletters (Subject-wise). Participate in the Sanfoundry Certification contest to get free Certificate of Merit. Join our social networks below and stay updated with latest contests, videos, internships and jobs!

Youtube | Telegram | LinkedIn | Instagram | Facebook | Twitter | Pinterest
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

Subscribe to his free Masterclasses at Youtube & discussions at Telegram SanfoundryClasses.