difference between co-pole and cross pole in antenna pattern

Hi,

The 'pole' is polarization.

So, one electromagnetic wave can be characterized by her polarization of the electrical field (E-field) :
in the orthogonal plane of propagation, the E-field can be moving in several ways.

If the E-field describes one ellipse : the polarization is elliptical
If the E-field describes one circle (heliax in reality, versus of time) : the polarization is circular left-hand or right hand.
If the E-field describes one straight line : the polarization is linear.

http://en.wikipedia.org/wiki/Polarization_(waves)

But the polarization wave of any antenna is not perfectly.
Example, one antenna that works in left-hand polarization (co-polarization) has one component, the 'cross polarization' (much smaller) of right-hand polarization.
This cross-polarization is radiated like the co-polarization and can be observed through the patterns radiation.

Look on courses or the web the link between 'AXIAL RATIO' and 'CO/CROSS POLARIZATION'.

BR

hi
then the desire polarization is same co-pol?
am i right?

Yes; "co" in this case means "the same", so "co-pol" = "the same" polarization.

This term looks to be borrowed from another radio field where "co-channel" means "the same channel" (as opposed to, or in contrast to, 'the adjacent' channel, which is the next channel up or down from the present 'channel' under consideration.)

RF_Jim

thanks RF_Jim