Antennas Questions and Answers – Types of Baluns

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This set of Antennas Question Bank focuses on “Types of Baluns”.

1. Which of the following statement is false regarding Type-1 Sleeve Balun?
a) It is shorted at the base
b) It has a λ/4 sleeve
c) It has a λ/2 sleeve
d) Ideally it provides infinite impedance at top
View Answer

Answer: c
Explanation: Sleeve Balun has a λ/4 sleeve which is shorted at base electrically and it provides infinite impedance at the top.
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2. Consider a 9:1 Balun (unbalanced to balance conversion); if the unbalanced impedance is RΩ then the balanced impedance will be _____Ω.
a) 9R
b) 3R
c) 0.11R
d) 0.45R
View Answer

Answer: a
Explanation: A 1:9 Balun represents that the balanced impedance is 9 times the unbalanced impedance.
⇨ Balanced impedance =9×R=9R

3. Which of the following Balun changes the shape of the unbalanced transmission line to that of a balanced transmission line?
a) Sleeve Balun
b) Folded Balun
c) Tapered Balun
d) Infinite Balun
View Answer

Answer: c
Explanation: Tapered Balun changes the shape of the unbalanced transmission line to that of a balanced transmission line. Sleeve Balun uses a λ/4 sleeve which is shorted at base electrically and it provides infinite impedance at the top. Infinite Balun uses the current flowing outside the conductor as a part of antenna.
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4. In which of the following Balun we don’t choke the current?
a) Sleeve Balun
b) Folded Balun
c) Tapered Balun
d) Infinite Balun
View Answer

Answer: d
Explanation: Infinite Balun uses the current flowing outside the conductor as a part of antenna. In this we don’t choke the current, but we use it as a part of antenna, where we want the current flow in it.

5. Which of the following Balun contains a sliding short circuit bar for frequency adjustment?
a) Type – 1
b) Sleeve Balun
c) Type – 2
d) Type – 3
View Answer

Answer: d
Explanation: Type – 3 Baluns has a sliding short circuit bar for frequency adjustment. Sleeve Balun or Type -1 Balun has a λ/4 sleeve which is shorted at base electrically.
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6. Type II Balun has two Type I balloons in series providing more bandwidth and load impedances at all frequencies.
a) True
b) False
View Answer

Answer: a
Explanation: Type II Balun has 2 Type I Baluns in series providing more bandwidth and load impedances at all frequencies. Type -1 Balun has a λ/4 sleeve which is shorted at base electrically.

7. Reciprocity applies to which of the following devices?
a) Isolator
b) Circulator
c) Balun
d) RF amplifiers
View Answer

Answer: c
Explanation: In a Balun, a 3 port network, contains one matched input and two differential outputs. It is used to convert the unbalanced signal to balanced and vice-versa. So it is reciprocal. Isolator, Circulator, RF amplifiers are Non reciprocal devices.
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8. For a Balun to work effectively, it must have ____ impedance for common mode currents and ____ impedance for differential mode current.
a) high, low
b) low, high
c) high, high
d) low, low
View Answer

Answer: a
Explanation: Since Balun have to minimize the common mode currents it should have High impedance.
For differential mode currents it must have low impedance.

Sanfoundry Global Education & Learning Series – Antennas.

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

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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