polarization reconfigurable antenna, which
can offer various polarizations at the same operating frequency,
has received considerable attention because it has the potential
to improve the performances of wireless communication
systems. For example, the switchable polarization antenna can be
used to mitigate signal fading in multipath propagation environments
and provide double transmission channels for frequencyreuse
radio transceivers; moreover, it can be applied to multisystemoperation
in orderto reducethe numberofthe required antennas.Forsingle-fedmicrostrippatchantennas,asimplemethod
to achieve the polarization switching is by changing the electric
characteristics of perturbation segments through PIN diodes, and
several polarizationreconfigurableantennasbasedonthemethod
have been proposed [1]–[7]. These past works mainly concentrate
on the designs related to the switching between left-hand
circularpolarization(LHCP)andright-handcircularpolarization
(RHCP) or between linear polarization (LP) and circular polarization
(CP). However, relatively few designs which can provide
dual orthogonal LP and even quadri-polarization diversities are
proposed. A reconfigurable aperture-coupled microstrip antenna
with a quadri-polarization diversity has been reported lately [8],
but it is a dual-fed design and the number of the required diodes is
eight, which would make the antenna structure and dc-bias network
complicated.