Hmmm

Well I can see that the term doesnt have a rigid definition as such. The
antenna part is obvious and I hope doesnt need me to elaborate. The word
microwave generally means a "small wavelength", probably anything higher
than the frequency of 1Ghz but it may be defined more accurately
elsewehere. The wavelength is inversely proportional to the frequency
and at 1GHz is about 300mm.

Microwave communciation is generally characterised by short distances
and line of sight or visible paths between one end and the other.
Examples might be mobile phones (900MHz, 1.8GHz, 2.4GHz), WiFi computer
links (2.4GHz, 5.6GHz), high capacity data links (2-25GHz) and so on.
(1000MHz=1GHz) Once the path becomes obstructed or goes over the horizon
the signal gets severely attenuated.

Antennas are designed and manufactured for the service and range required.

- Something to control a toy truck with you'll want to radiate in as
wide as a coverage angle as possible. When you tilt the controller back
and forth you still want it to work. Keep in mind that microwave
radiation also reflects of objects pretty well, so for short range this
is often the mode of operation.
- A WiFi antenna on a laptop and a users mobile phone generally needs to
radiate in a roughly horizontal direction but at every azimath. By
concentrating the radiation in a desired direction you get better range
or can get away with using less power. The WiFI and mobile phone base
station on tbe other hand may have more stringent radiation and
directionality requirements. The service area may be deliberately
restricted by the choice of antennas
- A high capacity microwave data link will pretty well always use high
gain high directive antennas at each end. This is so you can make the
signal work (say) upto 50km with low power. It is also very important
for these links to only have a direct (non reflective) path between each
other. The extra time delay introduced by a reflection can foul up the
link operation. (You may have heard the term "multipathing")

Generally speaking an antenna is made up of half wavelength elements at
the desired frequency, arranged to concentrate the radiation in the
desired direction. (look up the antenna terms 'colinear' and 'yagi')
More in common use are antennas that use large reflectors behind the
element connected to the cable. (look up 'parabolic dish', 'gridpack' &
'patch antennas'. What you see on a comms tower is the same theory of
operation as a deep space tracking dish.

The theory of operation of a microwave antenna is pretty much the same
as an antenna made for a lower frequency, just everything is much smaller!

From here on in you'll have to do some research on what antenna gain is
and how to build it into the structure.

Cheers Bob VK2YQA

Bug3 wrote:

Wondering what are microwave antennas, what do they do, how do they
work, etc?