open problems in antennas

Hello All,
Dose any one know what are the current open problems in Electromagnetics & Antennas?
Some of the fields to openly do research which I know are MIMO,Smart Antennas,Active & passive antennas etc etc but still I am not very specifically know about it.Also I know that application of GA and ANN to old problems on optimization are also good thing,and I am considering this as open problem option.
In electromagnetics I know scaterring by solid surface is still open problem but not sure of it.
Dose anyone know few open problems which can be openly targeted?
Thanks in advance.

Antennas are always too big. Make them smaller, with more gain and efficiency. And by the way increase both beamwidth and gain simultaneously. I ma asked to do that every day.

They also have to cost less and have greater bandwidth.