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Microfielder (Electrical)
16 Sep 09 14:20
Will a patch with very high er (80) bring the near field/far field boundary closer to the antenna by concentrating the radiated field more closely to itself?
Thank you  
Higgler (Electrical)
18 Sep 09 19:28
The near to far field boundary will be closer because the patch antenna will be physically smaller due to that high dielectric loading.

It's not a concentration due to dielectric that changes the answer to your question, it's just a physical difference in antenna size. Larger antennas have a longer distance inherently to the far field region.

Two antennas of the same physical size have the same near field/far field distance. That distance isn't simply 2d^2/Lambda either, it's much closer. All depends on what you plan to do.

d^2/Lambda has only 1/2 dB inaccuracy compared to 2d^2/Lambda for standard antennas being tested.

0.4d^2/Lambda distance from the antenna is typically the peak power density. Good to know if you are transmitting and worry about burning up a radome or human. i.e. if you make a large radome for a smaller transmit antenna, spacing it away from your antenna might burn it up if you put it 0.4d^2/Lambda away.

kch

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