Microwave Engineering Questions and Answers – Terminated Lossless Transmission Lines – 1

This set of Microwave Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Terminated Lossless Transmission Lines – 1”.

1. When a lossless line is terminated with an arbitrary load impedance ZL, then it :
a) causes wave reflection on transmission lines
b) transmits the entire supplied power
c) causes loss in transmission line
d) none of the mentioned
View Answer

Answer: a
Explanation: When a line is terminated with a impedance other the characteristic impedance of the transmission line, It results in reflection of waves from the load end of the transmission line hence resulting in wave reflection in the transmission line.

2. We say a transmission line is matched when:
a) ZL=Z0
b) ZL=√Z0
c) ZL=Z0/2
d) ZL=2Z0
View Answer

Answer: a
Explanation: We say a line is matched only when the characteristic impedance of the transmission line is equal to the terminating load impedance. Hence condition for a line to be matched is ZL=Z0.

3. Voltage reflection coefficient can be defined as:
a) ratio of amplitude of reflected voltage wave to the transmitted voltage wave
b) ratio of amplitude of reflected voltage to the incident voltage wave
c) ratio of load impedance to the characteristic impedance of the transmission line
d) none of the mentioned
View Answer

Answer: b
Explanation: From transmission line theory, reflection co-efficient of a transmission line is defined as the ratio of amplitude of reflected voltage to the incident voltage wave.
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4. Expression for a voltage reflection co-efficient in terms of load impedance and characteristics impedance is:
a) (ZL– Z0)/(ZL+ Z0)
b) (ZL+ Z0)/(ZL– Z0)
c) ZL. Z0/( ZL+ Z0)( ZL-Z0)
d) (ZL+ Z0)( ZL-Z0)/ ZL. Z0
View Answer

Answer: a
Explanation: The amplitude of the reflected voltage wave at the load end is equal to the difference between the load and the characteristic impedance, incident voltage is proportional to the sum of the load and characteristic impedance.

5. If a transmission line of a characteristics impedance 50 Ω is terminated with a load impedance of 100 Ω, then the reflection co efficient is:
a) 0.3334
b) 0.6667
c) 1.6
d) 1.333
View Answer

Answer: a
Explanation: Expression for reflection co-efficient of a transmission line is (ZL– Z0)/(ZL+ Z0) .substituting the given values of load and characteristic impedance, we get reflection co-efficient equal to 0.3334.

6. Return loss for a transmission line in terms of its reflection co efficient is given by:
a) -20logl┌l in dB where ┌ is the reflection coefficient.
b) -10logl┌l in dB where ┌ is the reflection coefficient
c) -10log (1/l┌l) in dB where ┌ is the reflection coefficient
d) -20log (1/l┌l) in dB where ┌ is the reflection coefficient
View Answer

Answer: a
Explanation: Return loss signifies the amount of energy reflected back from the load which is proportional to the reflection co-efficient of the line. Return loss in dB is given by the logarithm of the reflection co-efficient.

7. If the reflection coefficient for transmission line is 0.24, then the return lossin dB is:
a) 12.39dB
b) 15dB
c) -12.39dB
d) -15.2dB
View Answer

Answer: a
Explanation: The return loss of a transmission line, given the reflection co-efficient is -20logl┌l in dB where ┌ is the reflection co-efficient. Substituting for reflection co-efficient in the above equation, return loss is 12.39dB.
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8. Expression for VSWR in terms of reflection co-efficient is:
a) (1+│┌│)/(1-│┌│)
b) (1-│┌│)/(1+│┌│)
c) 1/│┌│
d) 1/1+│┌│
View Answer

Answer: a
Explanation: VSWR is the ratio of maximum amplitude of the standing wave formed to the minimum amplitude of the standing wave, when these voltages are expressed in terms of reflection co-efficient, we get the expression(1+│┌│)/(1-│┌│).

9. If the reflection co-efficient for a transmission line is 0.3, then the VSWR is:
a) 0.5384
b) 1.8571
c) 0.4567
d) 3.6732
View Answer

Answer: b
Explanation: VSWR (voltage standing wave ratio) in terms of reflection co-efficient is given by (1+│┌│)/(1-│┌│).substituting ┌=0.3 in this equation we get, VSWR=1.8571.
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10. If a transmission line of characteristic impedance 50 Ω is terminated with a load impedance of 150 Ω, then VSWR is:
a) 0.75
b) 0.5
c) 2
d) none of the mentioned
View Answer

Answer: b
Explanation: VSWR (voltage standing wave ratio) in terms of load and characteristic impedance is given by ZL– Z0 /ZL+ Z0. Substituting for ZL and Z0 in the above equation, VSWR is 0.5.

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]

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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.

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