cross polarization and co-polarization

Hiii...can u please tell me the differnce betwwenn cross-polarization and co-polarization?? what should be the range of cross-polarization and co-polarization while designing an antennaa?? how to calculate these parameter from radiation pattern in IE3d....plaease help me

Any antenna is designed to radiate or receive certain polarization. The design results also in ortho- to copol ratio. For good results, this ratio should be more than 20 dB but it also depends on the system in which antenna will be used, and the opposite antenna (sometimes the same type, sometimes not).

If your antenna is linearly polarized, the 3D pattern indicates a maximum and a minimum, so you can estimate the ortho-copol ratio from it. With circular polarization you must get the 3D patterns fo each polarization for it.

Real antennas can be measured against a calibrated reference antenna, best on an open range.

Polarization refers to the direction of the electric field. An antenna receptive (maximum response) to the particular field is co-polarized. Radiation with the electric field rotated 90 degrees is cross polarized.

Stutzman has published a book, Polarization in Electromagnetic Systems that goes into significant detail on the subject. Less detail can be found in most antenna books.

The basic idea, co-polarized implies a strong response and cross polarized signals, no reception.