3 ms·
By the principle of reciprocity, such an antenna also shouldn't couple at all to the far field of a distant radiating source... Right? So this should work well
by jbay808 5y ago
By the principle of reciprocity, such an antenna also shouldn't couple at all to the far field of a distant radiating source... Right?
So this should work well for a near-field coupling device, but not as some kind of distant silent receiver.
The "macroscopic atom" analogy makes me wonder, because atoms can absorb traveling photons just fine. But then again, only as well as they also radiate.
- petschge 5y agoIf it only receives the near field, can I used that to subtract the near field from a close-by regular antenna? That should make it more immune to local influences and improve the SNR of a far away signal?
- jpmattia 5y agoUnless I'm missing something, I don't think reciprocity helps you much here. There is a contained radiation field when the antenna is excited; there are no fields far away. Now when you start with no fields far away, it doesn't tell you much about the excitation near the antenna. You can envision some radiation pattern from far away antennas which have overlap with the near-field modes. As a consequence, some amount of energy will be received by this antenna. Naturally it depends on how well the near-field mode is excited as to how much coupling occurs.
- jbay808 5y agoWhat I mean by reciprocity is, if distant far-field antenna B can transfer energy to our contained-field antenna A, then shouldn't our contained-field antenna A also be able to transfer energy to the far-field antenna B? Wouldn't that be inconsistent with A not having a far-field emission? If A doesn't produce any field at B, then it doesn't seem possible that the field B produces at A could be absorbed by A. Thermodynamics should guarantee this, otherwise you could use it (in a roundabout way) to violate the second law.