antenna cross section

Hello
I am going to simulate a dipole antenna and I want to plot its cross section (both scattering and absorption). I know scattering cross section and absorption cross section must been considered outside and inside of device respectively but I do not know exactly their positions. for instance, absorption cross section should contain antennas plus gap or it should contain just one of antenna!

Thanks

Most folk in this forum would need more information to try and help you.
Firstly, what is the frequency it is intended to operate at?
Next is whether it is a full resonant length (half-wave), and whether or not it is straight. one needs an idea of the dimensions.
Also helpful is the simulation method. Is it by NEC-type "Method of Moments, or is it using some other simulation tool?

Normally, if the "gap" where the generator simulator is placed is a small fraction of the total length, the pattern obtained is not affected. Say 1 or 2 percent of the length.

When you say "scattering" and "absorption", this implies there are nearby grounded structures to be considered. Unless there are fast equivalent models available, this could be in the territory of long and difficult computation. For wire and rod structure antennas into the UHF range, most NEC2 type Integral Equation Method of moments solutions are reasonably accurate, and much faster than full surface current EM simulation.

Unfortunately, the method can get unworkable quite quickly if matrix gets too large from complex detail.

Thanks
This device works in THz frequency and it is full resonant length.
Its dimension is micron but some of its length is in nano meter range.
and of course my simulation method is FDTD. It is important that it works in plasmon mode.

Thanks

OK - so thats a less usual frequency (for me anyway). I don't know how the dipole current is normally excited in the simulation tool you use, but generally if the "gap" where the source is placed is less than 0.1% of the length, the field is the same as for a simple dipole resonating.

So far as I know, a conducting dipole, whatever the size, even at atomic dimensions, will have the properties of electric field between its ends, and magnetic field from the currents in it, and alternating energy storage in the near field. A transient excitation (FTDT) is also OK. Probably a large scale model of the entire structure with the frequency scaled as well might produce the same results.

Check out a link, valid at this time for a while at least, to a discussion of the merits of various FTDT simulation tools.

Current to reseachgate.net discussion--> LINK

While I expect you have your own FTDT simulation resources, I was pleased to discover the free FTDT solvers "MEEP", from MIT. and also "OpenEMS", apparently based on Octave (nee MatLAB ).

For the convenience of edaboard folk who might want a look, I post them here.

MEEP FTDT Solver from M.I.T --> LINK
OPenEMS FTDT Solver -->LINK