Using coplanar or multi-layer parasitic elements is the most
popular and useful method for bandwidth improvement. The
basic idea is to introduce additional patches to provide two or
more closely spaced resonances. In other words, creation of
multiple resonances in input response by addition of external
passive networks or internal resonant structures. In some
reported cases the additional elements may havc increased
the volume. and this should be borne in mind when assessing
the bandwidth improvement. These methods may invoke
additional dissipative losses.