Concern about polarization for antenna design

Can any one please explain to me how does the requirement of polarization actually affects the design of an antenna? e.g. Microstrip antennas?
Thx

You need to know the polarization of the transmit/receive antenna that your system is communicating with. They will need the same polarization to operate at maximum gain. Vertical to vertical, horizontal to horizontal, right-hand circular to right-hand circular, etc.

If transmit and receive polarizations are out of phase the receive signal can be down 20-30 dB. It's a bit like plugging a polarized AC connector into an outlet. Works best in the proper orientation.

Polarization is determined by where the patch is excited by the feed. Linear polarization is excited along the length of the patch. Circular excites both horizontal and vertical directions simultaniously splitting the power evenly but 90 degrees into both orientations which creates a rotating vector. The circularly polarized patch needs some sort of perturbation to length/width that exites the 90 degree phase difference between horizontal and vertical modes.

A simple introduction on polarization can be found here:
h**p://www.astronwireless.com/polarization.html