creating a linearly and circularly polarized antenna?

Hi,

I would like to know if you have some exemples of small antennas which are both linearly and circularly polarized antennas? and if you can explain to me how we can create both polarizations on an small antenna?

Thank you

A circular patch can do both if you have an appropriate feeding method (e.g., quadrupolar) -- but these will occur as a result of different modes being excited, and therefore possess different operating frequencies.

A cross dipole can generate all possible polarization variants (horizontal, vertical, left and right circular or elliptical) by adjusting phase and magnitude of both feed lines.

You can not do both at the same time.
But you can build antennas were you can switch between linear and circular polarization, best example is a crossed dipole.

A circular polarized antenna will receive a linear polarized signal fine but with a 3dB loss, same the other way around.