RF beam width and antenna diameter?

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SUMMARY

The discussion centers on the relationship between beam width and antenna diameter in directional RF antennas, highlighting that beam width is inversely proportional to the diameter of the parabolic reflector. The formula α = 1.22 λ/d radians is critical, where λ represents wavelength and d denotes antenna diameter. For example, at 3 GHz, the wavelength is 10 cm, resulting in significant differences in beam divergence compared to visible light, which has a wavelength of approximately 500 nanometers. The conversation also emphasizes the advantages of using multiple antennas, such as in the Very Large Array (VLA), to enhance signal quality and resolution.

PREREQUISITES
  • Understanding of RF antenna design principles
  • Familiarity with the equation α = 1.22 λ/d radians
  • Knowledge of wavelength and its impact on beam divergence
  • Basic concepts of diffraction and interference in optics
NEXT STEPS
  • Research the Very Large Array (VLA) and its antenna configuration
  • Study the effects of antenna spacing on beam width and signal quality
  • Explore advanced concepts in diffraction and interference in radio frequencies
  • Learn about the practical applications of parabolic antennas in telecommunications
USEFUL FOR

RF engineers, telecommunications professionals, and anyone involved in the design and optimization of directional antennas.

ctech4285
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it seems like looking at beam patterns from directional RF antennas the beamwidith is something like inversely proportional to the parabolic reflector diameter. why can you make an almost perfect strait parallel beam of light but not with RF?
 
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The angular divergence of an optical lens and a directional radio antenna is given by

α = 1.22 λ/d radians

where λ is wavelength, and d is antenna diameter.

For visible light, λ ~ 500 nanometers, and for a 3 GHz antenna, λ = 10 cm. Wavelength ratio is 200,000:1.

Bob S
 
what cause this?
what would happen if you use two directional antennas would the beam width be half on one plane? would it make a difference if you place them far apart?
 
Two parabolic antennas are better than one. 27 parabolic antennas separated by multiple wavelengths are better than two. See Very Large Array (VLA) antenna "farm" photo at

http://en.wikipedia.org/wiki/Very_Large_Array

Read about diffraction, interference, and resolving power of lenses (the equation α = 1.22 λ/d radians) in physical (conventional) optics books.

Bob S
 

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