Antenna Measurements Questions and Answers – Standing Wave Ratio Method

«
»

This set of Antennas Multiple Choice Questions & Answers (MCQs) focuses on “Standing Wave Ratio Method”.

1. Which of the following statement is true?
a) Standing waves occur when mismatches occurs
b) Standing waves occur when no mismatches occurs
c) Minimum value of SWR is 0
d) Maximum value of SWR is 1
View Answer

Answer: a
Explanation: When there is mismatch, reflections occur and this causes for the occurrence of the standing waves. The standing wave ratio is defined as the maximum voltage to minimum voltage.
\(S=\frac{V_{max}}{V_{min}} =\frac{1+ρ}{1-ρ}\) And reflection coefficient \(ρ=\frac{P_{ref}}{P_{inc}}. \) Therefore S ranges from 1 to infinity.
advertisement

2. Relation between SWR ‘S’ and reflection coefficient ‘ρ’ is given by _________
a) \(S=\frac{1+ρ}{1-ρ}\)
b) \(S=\frac{1-ρ}{1+ρ}\)
c) \(S=\frac{1+ρ}{ρ}\)
d) \(S=\frac{ρ}{1-ρ}\)
View Answer

Answer: a
Explanation: Standing waves occur when there is mismatch or reflection due to uneven surfaces. The standing wave ratio is defined as the maximum voltage to minimum voltage and its relation with the reflection coefficient is given as
\(S=\frac{V_{max}}{V_{min}} =\frac{1+ρ}{1-ρ}.\)

3. If there are no any reflections, then the value of the SWR will be ________________
a) 1
b) 0
c) ∞
d) 2
View Answer

Answer: a
Explanation: The standing wave ratio is defined as the maximum voltage to minimum voltage.
\(S=\frac{V_{max}}{V_{min}} =\frac{1+ρ}{1-ρ}\)
And reflection coefficient is \(ρ=\frac{P_{ref}}{P_{inc}} =0 \) (Since there are no reflections).
\(S=\frac{1+ρ}{1-ρ}=1\)
advertisement
advertisement

4. The value of the SWR when the reflection power is equal to the incident power is ____________
a) 1
b) 0
c) ∞
d) 2
View Answer

Answer: c
Explanation: The Reflection coefficient is \(ρ=\frac{P_{ref}}{P_{inc}} =1\) (Since there are reflections power and incident power are equal). The SWR S is given by
\(S=\frac{1+ρ}{1-ρ}=\frac{1}{0}=∞\)

5. Which of the following level can be measurable by the Low VSWR?
a) 15
b) 11
c) 9
d) 20
View Answer

Answer: c
Explanation: The low VSWR measurement is able to measure the readings of the VSWR not exceeding 10. For High VSWR measurements (S>10) there is a special method called double minimum method.
advertisement

6. The empirical formula for the measurement of the high VSWR is give by ____
a) \(VSWR =\frac{λ_g}{π(d_2-d_1)}\)
b) \(VSWR =\frac{λ_c}{π(d_2-d_1)}\)
c) \(VSWR =\frac{λ_g}{2(d_2-d_1)}\)
d) \(VSWR =\frac{2λ_g}{(d_2-d_1)}\)
View Answer

Answer: a
Explanation: High VSWR measurements (S>10) there is a special method called double minimum method. \(VSWR =\frac{λ_g}{π(d_2-d_1)}\) where d2, d1 are the readings noted on the slotted line where dips (3-db power) is observed.

7. Which of the following is not used in the VSWR measurement?
a) Reflective Klystron
b) Slotted line
c) Frequency meter
d) Spectrum analyzer
View Answer

Answer: d
Explanation: Spectrum analyzer frequency domain instrument and is contrast to the oscilloscope which displays in time domain. The Klystron acts as a microwave source and the by moving the slotted line the maximum reading on the meter is observed. For high VSWR the frequency of operation is noted using the frequency meter.
advertisement

8. The relation between the λg, λc, λ0 is given by ____
a) \(\frac{1}{λ_0} =\sqrt{\frac{1}{λ_g^2} +\frac{1}{λ_c^2}} \)
b) \(\frac{1}{λ_g}=\frac{1}{λ_0^2} -\frac{1}{λ_c^2} \)
c) \(\frac{1}{λ_0} =\sqrt{\frac{1}{λ_g^2} -\frac{1}{λ_c^2}}\)
d) \(\frac{1}{λ_g}=\frac{1}{λ_0^2} +\frac{1}{λ_c^2} \)
View Answer

Answer: a
Explanation: The relation between the λg, λc, λ0 is given by \(\frac{1}{λ_g^2} =\frac{1}{λ_0^2} -\frac{1}{λ_c^2} \)
⇨ \(\frac{1}{λ_0} =\sqrt{\frac{1}{λ_g^2} +\frac{1}{λ_c^2}}\)
and \(λ_0=\frac{c}{f}.\)

Sanfoundry Global Education & Learning Series – Antennas.

advertisement

To practice all areas of Antennas, here is complete set of 1000+ Multiple Choice Questions and Answers .

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!

advertisement
advertisement

Leave a Comment

Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn | Youtube | Instagram | Facebook | Twitter