Antenna Measurements Questions and Answers – Near Field and Far Field

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This set of Antennas Multiple Choice Questions & Answers (MCQs) focuses on “Near Field and Far Field”.

1. The region greater than \(\frac{2D^2}{λ}\) in an antenna with largest dimension D is called _____
a) Far field region
b) Near filed region
c) Radiative Field
d) Reactive Field
View Answer

Answer: a
Explanation: The characteristics of EM fields vary with distance from the antenna. It is divided into two regions. The region next to the antenna is the near field region and the region Far field region > \(\frac{2D^2}{λ}\).

2. Which of the following is known as Non Radiative region?
a) Far field region
b) Near filed region
c) Radiative Field
d) Reactive Field
View Answer

Answer: d
Explanation: Radiative and reactive field regions are the parts of the near field region. The Far field region is greater than \(\frac{2D^2}{λ}\)and near field region is less than \(\frac{2D^2}{λ}\). Reactive region is also known as non- Radiative region and is next to antenna. The Radiative region is also known as Fresnel region.

3. Which of the following is true?
a) Radiative Field < 0.62\(\sqrt{\frac{D^3}{λ}}\)
b) Reactive Field < 0.62\(\sqrt{\frac{D^3}{λ}}\)
c) Fresnel Field << 0.62\(\sqrt{\frac{D^2}{λ}}\)
d) Near field > \(\frac{2D^2}{λ}\)
View Answer

Answer: b
Explanation: The characteristics of EM fields vary with distance from the antenna. It is divided into two regions. The region next to the antenna is the near field region and the region Far field region > \(\frac{2D^2}{λ}\). Reactive field < 0.62\(\sqrt{\frac{D^3}{λ}} < \,Radiative\, field\, < \frac{2D^2}{λ}\).
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4. Radiative and Non Radiative fields are parts of which field region?
a) Near field
b) Fresnel field
c) Reactive field
d) Far field
View Answer

Answer: a
Explanation: The Near field region is less than \(\frac{2D^2}{λ}\) the Far field region is greater than\(\frac{2D^2}{λ}\). Radiative and reactive field regions are the parts of the near field region. Reactive region is also known as non- Radiative region and is next to antenna. The Radiative region is also known as Fresnel region.

5. Near field is also known as inductive field.
a) True
b) False
View Answer

Answer: a
Explanation: The region next to the antenna is the near field region and it is less than \(\frac{2D^2}{λ}\). Near field has inductive effect hence it is also known as the inductive field. The far field is known as the radiating field as radiation is high in that region.
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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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