Electronics and Communication Engineering - Microwave Communication - Discussion

22. 

The width of a radio beam from a 1 m diameter parabolic antenna at 10 GHz is about

[A]. 100°
[B]. 50°
[C].
[D].

Answer: Option C

Explanation:

.


Jagriti said: (Dec 23, 2014)  
What is 140?

Lavanya said: (Jan 16, 2015)  
140 is for antenna factor.

Goldy said: (Jul 14, 2015)  
Please explain in detail.

Aravind said: (Aug 1, 2015)  
140c/wavelength.

Rose said: (Sep 30, 2015)  
Kc/wavelength.

Where k is a factor which varies slightly depending on the shape of the reflector and the feed illumination pattern. For an ideal uniformly illuminated parabolic reflector and θ in degrees, k would be 57.3 (the number of degrees in a radian). For a "typical" parabolic antenna k is approximately 70.

How 140?

Dhruv said: (Jun 8, 2016)  
@All.

Beam width b/w half power points in a parabolic reflector = 70 * (lambda/diameter).

Therefore, beam width b/w first nulls = 2 * half power bw.

Then, we get 140.

Sankar said: (Oct 14, 2017)  
I think 140 (λ) /diameter then we get above equation.

Ayush Kumar said: (Nov 3, 2017)  
Yes beam width = 140(lambda)/diameter.

Sreeram said: (Feb 15, 2018)  
(140 (wavelength))/diameter.

Asus said: (Jun 24, 2018)  
Why 140?

Zecru said: (Dec 19, 2018)  
We use 70 for the Half Power Beam Width only.

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