Wireless technologies are playing an increasing role in the lives
of people throughout the world. In addition, ever-larger
numbers of people are relying on the technology directly or
indirectly. Wireless technologies such as cellular phones,
wireless devices, and wireless local area network (WLAN)
have brought mobility and flexibility to our lives.
Mobile phones, base stations and other wireless technologies
work by sending radio signals through the air to connect the
transmitters and receivers, in the same way as radio and TV
technologies which have been around for many years. Mobile
phone handsets use the microwave part of the electromagnetic
spectrum, which is next to the infrared region. This feature
summaries the main mobile and wireless technologies currently
in use and compares them with mobile phones in terms of their
power. For instance, for two WLAN systems installed in close
proximity, signals may propagate from one system to another.
The signal noise will affect the interference may not only
degrade the system performance causing packet losses and
throughput reductions, the undesired interference can be
reduced significantly in power.
FSS have been used in military applications, antennas, radar,
and satellite communications for many years [1]. In the near
infrared wavelength region, frequency selective surfaces are
primarily used in filtering applications. Some applications
include band-pass filters, polarizers, and beam splitters.If theperiodic elements within a FSS possess resonance
characteristics, the inductive FSS will exhibit total transmission
at wavelengths near the resonance wavelength, while the
capacitive FSS will exhibit total reflection [2-4]. This feature
allows a FSS with the proper elements to perform like a narrow
band-pass filter. Similarly, a complimentary design can be
created to selectively reflect narrow band-pass regions. Specific
applications of these types of FSS filters include narrowband
astronomy filters, and filters for spacecraft instrumentation[5].
Filters play a fundamental role in almost electronic or RF
circuit. Once being incorporated into a design, the filter acts as
a device that controls the frequency content of the signal for
mitigating noise and unwanted interference. Spatial filters, or
frequency-selective surfaces, are formed by periodic arrays of
usually metallic elements on a dielectric substrate. FSS most
commonly take the form of planar, periodic metal-dielectric
arrays in two dimensional spaces. Frequency behavior of an
FSS is entirely determined by the geometry of the surface in
one period (unit cell) provided that the surface size is infinite.