Focusing electromagnetic field

using electrical or magnetic field you can, this is done in CRT monitor, CRT CRO, etc,

I want to do near field focusing with reduced spot size...

See tappered metamaterial lens in IEEExplorer. I believe, Shalaev and Grbic were publishing some. I think, it is similar to normal antenna array. Or in MM terms, the refraction index is modulated to achieve the effect with geometrical optics approach. It is actually not that simple as it seems, because such lens are polarization-related.
But normally, people do this with polymer lens. Just polystyrene condensing lens like you use glass lens in visible optics.

No it is not. CRT & CRO etc do not have an EM field inside.



Any device which is classified as an RF antenna is basically doing just this - focusing an EM field.

To achieve focusing to a specific point, the best way is to use a parabolic dish. However the size, material etc etc of such a dish depends on your frequency of interest.

So what IS your freq(s) of interest ?

My frequency of interest is 10 ghz.....need to design he antenna with reduced FWHM.

There is lots of info available on the net. Just google for 10Ghz dish antenna, or Ku band dish antenna.

For reducing the 3dB width, you would typically use a larger parabolic dish.

Thank you...