Questions tagged [far-field]

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How to calculate far field distance from an antenna

I understand the formula for calculating the far field distance from an antenna is: Distance = (2D^2)/λ Is the D in the above equation the length of the antenna under test (antenna under test is a ...
• 340
85 views

What is >> (double chevron) in far field communication

I keep seeing this notation with no justification or explanation as to what it is – it appears to be being used as greater than but I don't know why > isn't sufficient. Didn't want to ask it as a ...
• 346
1 vote
39 views

Using a far field UHF RFID in the near field range

I have a 902 MHz to 928 MHz UHF 8dBi far-field RFID antenna connected to a reader. I want to read RFID tags. What will be the consequences if I used this UHF antenna in the near field range when it is ...
• 1,275
261 views

Rayleigh distance of array antenna

Far field zone of a single antenna can be determined by using the equation below. $$R>\dfrac{2D^2}{\lambda}$$ Where D is the biggest dimension of the antenna. This equaiton is suitable for single ...
27 views

662 views

Transformer basics: Why don't they shift phase by about 90°?

I learned that current is induced in a conductor by a changing magnetic field. According to this, it would follow that the secondary voltage (sinusoidal input) of a transformer should peak when the ...
97 views

The electric and magnetic components of far field EMR and shielding thereof

This is a newbie question. I'm pretty sure of the answer, but I would like confirmation. I found this thread in this forum that came close to what I was looking for, but I think my question is ...
• 311
281 views

Phased array minimum size

I want to know two things,how big does the phased array needs to be to form proper beam and what is the smallest area the beam can be focused.I learned little bit about lasers and with focal lense,the ...
529 views

What are the extra lines on this farfield plot?

This is a plot from CST microwave studios of the farfield beam pattern of an antenna. I'm having trouble understanding why the plot isn't single-valued (2nd red circle) and also why there are blue ...
• 105
1 vote
543 views

Relationship between electric field at aperture and field at distance

I'm new to this forum and turned here because I have no other help to turn to. In studying antenna theory and I came across the relationship between E0(Electric field at aperture) and Er(Electric ...
2k views

How is the minimum reasonable distance for the far field of a dipole antenna calculated?

First let me try to explain what I think the near field is about: At very close ranges, due to the differences between instantanous voltage and current on each small segment of an antenna at any ...
• 115
2k views

near field power density formula for a dipole antenna

I am looking for a formula for near field power density from a dipole antenna antenna. Is cylindrical model is sufficient? Do I have to consider ground reflection too? Please share your ideas?
863 views