Something you may not have given a lot of thought to before
are the different types of wireless antennas available
for specific use cases.
Knowing these differences and knowing
how an antenna operates
will help your choose the correct antenna
for your enterprise needs.
So in this video, we'll now compare the features
of some of these various antenna types.
The first characteristic that we want to look at
is the radiation pattern of an antenna.
Very simply, this is the measure of the signal strength
that you would find around the antenna.
It's a bit tricky to get your head around,
but you want to know that this radiation pattern
is measured as a 3D shape.
When we plot 2D objects, we have only two axes,
an X and a Y.
When we have 3D shapes,
we have to add an additional Z axis.
If we look at the point where the X-Y plane cuts
our spherical radiation pattern that we see here,
if we pull that out,
this is what we refer to the "H" plane,
or the horizontal plane.
When we're examining the radiation pattern,
the H plane is one of the characteristics
that we can measure.
Likewise, if we cut the sphere along the X-Z plane,
this is what we call the "E" plane, or the elevation plane.
These can been extrapolated into a circular plot graph
as we see here, where the innermost rings
represent the weakest signal strength,
and of course, we see sectors represented
in 360 degrees as well.
We can use a different plot path for each direction,
so we can use a plot graph for the H plane
and another plot graph for the E plane.
Different antennas will have different radiation patterns
that may make them more suitable in certain cases.
There are two basic types of antennas that we will look at
and those are omnidirectional and directional,
and those both have two distinct radiation patterns.
Omnidirectional antennas are probably
what you're most familiar with.
As you can see, a common example
is a cylindrical-shaped antenna
such as what you would find
on almost any consumer-grade wireless router.
These are designed so that the radiation pattern
propagates the signal away from the cylindrical antenna
in all directions in a spherical shape,
so you can probably guess
that this is what makes them suitable
for small office or home office use,
because they radiate in all directions.
This particular common omnidirectional antenna
that we see here is referred to as a dipole
because there are two wires inside of the antenna
that carry alternating current,
and these are what generates the RF signal.
Sometimes these are in a fixed position,
and other times they have a pivot point as we see here,
and that will allow them to swivel 90 degrees.
But dipole omnidirectional antennas,
you want to know that they are designed
for widespread coverage.
If we look at the radiation pattern
for omnidirectional antennas,
you can see the H and E planes
represented here on these graphs.
The E plane represents a side view of the antenna,
while the H plane represents a view from the top.
We can see that the antenna has the weakest signal.
If we look at the E plane, the signal is weakest
at the top and the bottom of the antenna.
If we look at it from above,
we have a fairly circular pattern.
So this creates a sort of donut-shaped radiation pattern.
Sometimes there are multiple smaller versions
of these omnidirectional antennas embedded into a device
rather than having an unsightly external antenna
such as with the Cisco Aeronet Series.
The coverage with these is almost exactly the same
with the integrated omnidirectional antennas
offering a little bit better coverage
above and below the device.
Then we have a category of antennas
called directional antennas.
As you can probably guess,
these have their RF radiation pattern
focused in a specific direction
rather than trying to provide broad coverage of an area.
And because of this, these typically have higher gain
than omnidirectional antennas.
There are many examples of these that we can see here,
including patch antennas, Yagi antennas, and dish antennas.
If you have a really long hallway,
maybe in a hospital or a large warehouse,
these sort of directional antennas
can offer coverage in very specific directions
and even over very long distances.
This can also be used to extend wireless networks
to other buildings, if we use
a line-of-sight RF signal transmission.
If we look at the radiation pattern of this type of antenna,
you can see that this is very concentrated.
It looks much differently than the omnidirectional antennas.
This is a very focused beam extending
in a single direction almost entirely.
It should go with saying that when comparing
omnidirectional and directional antennas
that omnidirectional antennas are going to have
a lower gain than directional antennas do.
In other words, they have a less focused RF signal path.
So that's a look at the different types of wireless antennas
that we have at our disposal.
Depending on your own application,
there are lots of different antenna varieties to choose from
in order to make sure that you get the coverage you need
in your enterprise environment.