# Dipole Receive Antenna: Derivation of circuit representation

Many textbooks cover generation of electromagnetic radiation via transmit antenna and then invoke a reciprocity theorem for the antenna acting as a receiver.

I'm wondering, can you derive the equivalent circuit representation of a (short)dipole receiving antenna from base principles?

For a short dipole antenna, how would this be derived?

• suggest you migrate this to the amateur radio stack exchange. Lots of antenna experts there. – niels nielsen Jul 13 '18 at 23:58
• This is physics and is a good question. I have not seen derivation of that kind and the reason given is always that such way is more complicated, so why not use the reciprocity principle. The difficulty is of course that for a receiver antenna you must account for scattering in all directions unlike in a transmitter where the reflection is in one mode that is propagating in the transmission line. – hyportnex Jul 14 '18 at 13:01
• I would also be interested in an explanation why the effective area of a dipole antenna is much greater than its physical surface area. I saw a link to an article about why EM waves can be absorbed by a greater area then the physical object but it was behind a pay wall and I couldn't get to it. I would ask the amateur radio exchange but given the questions technical nature I don't know if it would help. – FourierFlux Jul 14 '18 at 21:36
• What do you mean from base [first] principles? The usual derivation just assumes fields excited on the structure and derives the radiated fields $\vec{E}$ and $\vec{H}$. You can get the radiation resistance from that. – AntennaGuy Aug 8 '18 at 18:28
• If you want to go to a circuit model, you can use electrically small antenna theory to determine some equivalent circuit. Typically, this is just an LC with an R attached (R being total resistance, sometimes broken up as radiation and loss). The values of the L and C could be derived from the $\vec{E}$ and $\vec{H}$. the number of series LC resonances depends on how many terms you truncate in the expression (i.e. far-field approximation or not). There's TONS of literature on "theory of electrically small antennas," and circuit representations. – AntennaGuy Aug 8 '18 at 18:28