Techniques for making antennas smaller have long been
established [8.9-10]. Their aim is to achieve resonance at the
desired operating frequency in a smaller size. There is a
fundamental trade off between bandwidth and size. so the
miniaturization techniques incur penalties in bandwidth. and
sometimes also efticicncy. These may be acceptable in
particular applications. The main miniaturizing tools used are
loading the antenna with lumped elements. high dielectric
constant materials. or with conductors: using a ground plane
and short circuits, and optimising the conductor geometry.
Loading of the antenna can be done by modieing the
dielectric or magnetic characteristics of the material
surrounding it. The antenna becomes smaller when
embedded in high-permittivity material. due to the reduced
wavelength in the material. Higher permittivity usually
implies higher dielectric losses. but these can remain very
small with modern dielectrics. However, the size reduction in
itself tends to increase conductor ohmic losses. Another