2.) You would like to measure the exposure created by
each individual appli-
cation
, for example, to evaluate excess of exposure limits.
Regarding 1.):
Let’s reconsider our ‘giant motorway’ example:
Remember that every lane was only intended for the use of a single kind of
vehicle. Now imagine that a huge bridge crossed this motorway and you stan-
ding on the bridge and looking down on the motorway. Wow, what a mess!
Now, imagine you would like to know what exactly happens on the motorway,
seperately per lane. As the motorway is incredibly wide, you will need some
quite good binoculars, even if you only want to have a small overview. Let’s ima-
gine that you can evaluate a range of 400m with your binoculars. Next, you
would like to determine what lanes have traffic right now and how fast it is going.
Consequently, you will take a piece of paper and note the corresponding lane
number and measured speed. Starting at lane 1, you write down: nothing! OK,
next, lane 2: nothing either! OK, lane 3: yes, there’s something going at 18km/h.
Lane 4: nothing. And so on - until you have reached the last lane. What have you
achieved? Well, you have just performed an
analysis
of the entire lane
range
of 0-400m. Or, in other words: you have performend a
RANGE
ANALYSIS.
Analysis, as you know, means dividing something into smaller pieces and eva-
luate those. In our case, the wide motorway was that “something“, and the smal-
ler pieces were the individual lanes. Now, the word “range“ can be replaced with
the word “
SPECTRUM
“, and there we are: we have just performed a
SPEC-
TRUM ANALYSIS
! Well, who would have thought that you are a
spectrum ana-
lyser!
But joking aside: now the only thing missing is a “lane plan“ which would provi-
de detailed information which lanes correspond to which vehicles, and you can
determine exactly what vehicles were just been travelling.
That’s exactly what happens when doing
spectrum analysis
:
There are “lanes“ here as well, just that these lanes are called
frequency ran-
ges
. The width of these
frequency ranges
is measured in
Hz
(Hertz). As very
often these ranges fall into very high
Hz
ranges, numbers would grow quite large
when actually using this unit. Consequently, the unit is often prefixed, resulting
in
kHz
(1,000
Hz
) or
MHz
(1,000,000
Hz
). This way, working with these numbers
becomes much more comfortable. Likewise, 1.000.000
Hz
could also be expres-
sed as 1.000
kHz
or 1
MHz
, and so on.
Firmware V 1.0 / © 2005-2013 by Aaronia AG, D-54597 Euscheid, www.aaronia.com
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19.0 Spectrum analysis basics
