# Questions tagged [far-field]

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### What does a far-field SPICE model for a 900 MHz antenna look like?

Without doing in-depth math for the EMI, I am trying to find a SPICE model for an antenna for a 900 MHz RFID system. My primary interest is circuits and not antennas per se, and using ADS and other ...
• 3,292
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### Why do we want detaching field lines in an antenna?

I have some questions about the link between the intuitive explanation for why an antenna radiates (based on this video) and the Maxwell equations. Q1. The video starts by saying that "an ...
• 3,550
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### Antennas Far field radiation pattern

I want to understand this Far field graph of an antenna generated in CST, from the picture: Is this a good radiation pattern? If yes, then how? How to explain the graph?
1 vote
506 views

### Antenna polarization and loss factor

I am trying to solve the following problem: I know that in the +z direction: linear polarization requires the field vector to have: one component OR two orthogonal linear components that are in ...
1k views

### How to calculate far field distance from an antenna

I understand the formula for calculating the far field distance from an antenna is: Distance = (2D2)/λ Is the D in the above equation the length of the antenna under test (antenna under test is a ...
• 412
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### 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 ...
• 436
1 vote
80 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 ...
• 2,391
1 vote
574 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 ...
43 views

1k 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 ...
146 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 ...
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### 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 ...
722 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
695 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 ...
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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?
1k views