Antenna, RF feeder and RF connector topics
RF antennas (or aerials) are an essential element of any
radio communications link, whether it is for a high power transmitter like those
used for broadcasting, or low power ones like those used wireless technologies
such as WLAN or remote control and sensing applications.
Apart from the power
levels, RF antennas are used across the whole radio spectrum, from ELF right up
to the microwave bands. Whatever the power, and the frequency, the basic RF
antenna design theory remains the same, although the practical approach has to
change to meet the differenting mechanical requirements.
Although RF antenna design and theory can involve a considerable amount of
involved mathematics, there is much that can be achieved with only a minimum of
mathematics, and most RF antenna engineers do not need a Ph.D in advanced
calculus.
RF Antenna Basics
Electromagnetic waves and basic antenna operation
Polarisation
impedance - including radiation resistance, loss resistance and
efficiency
Resonance and bandwidth
Directivity and gain
Feeders
The ideal position for an antenna is rarely in the optimum position for the
transmitting or receiving equipment. As a result a form of transmission line or
feeder is required to transfer the signals and power to and from the antenna.
Coaxial feeder
Coax
cable loss or attenuation the reasons for it and how to minimise it.
Coax cable power rating
Coax cable velocity factor
RF coax cable data and specifcations
Environmental factors relating to coax cables
Balanced feeder
Waveguide basics
Waveguide data
Antenna RF diplexer - although not a feeder, a diplexer is sometimes
included in the feed system of an antenna.
RF coax cable connectors
A wide variety of RF connectors are available for making connections to coaxial
cable. These connectors including BNC, C-type, N-type, UHF (Amphenol) connector,
SMA, SMB, SMC and many more are able to be used in a variety of applications.
Coax cable connectors - general overview
BNC connector
TNC connector
C-Type connector
N-Type connector
SMA connector
SMB connector
UHF connector
The dipole antenna
The dipole antenna is one of the most basic forms of antenna available. It is
widely used on its own, and it is also used as the "driven" element in many
other types of antenna.
The
dipole antenna
Folded dipole
The vertical antenna
Vertical antennas are widely used in many areas, and are particularly widely
used for mobile applications because they radiate all around them in the
horizontal plane. This means that they do not need redirecting as the mobile
station moves. The quarter wave vertical is the simplest, but there are many
other designs that provide improved performance and gain.
Quarter wave vertical
Five eighths wavelength vertical
J pole vertical antenna
Directional antennas
There is a good variety of different types of directive antenna that can be
used. Although the yagi antenna is the most popular, it is by no means the only
one, and other designs and approaches are more applicable in many instances.
Yagi
Log periodic beam antenna
Parabolic reflector
Horn antenna
Wideband antennas
Most antennas are only able to operate over a narrow bandwidth. There are some
techniques that enable the bandwidth of an antenna to be increased considerably,
and also some desgigns that are able to operate over very wide bandwidths.
Discone
Log periodic beam antenna
Loop antennas
Where directivity and small size are required, loop antennas may often provide
an answer. Although different types of loop have slightly different properties,
they are able to provide a good antenna solution in many circumstances.
Loop antenna overview
Ferrite rod antenna
Applications
Antennas can be used in many applications from reception of terrestrial and
satellite television to point to point radio, short wave radio and much more.
Satellite antennas for satellite television and other satellite applications
Antenna installation
When installing an antenna many points must be considered. Location, type of
antenna, method of installation and many other items all affect the antenna
installation. Safety is also a crucial element because if the antenna is not
installed correctly the antenna may collapse.
Antenna height
Antenna installation materials - choosing the correct materials to minimise
corrosion
How to install coax cable - some key points to note
