Frequency Calculation Examples; Example 1: A Simple Sweep - Agilent Technologies PSA Series User Manual

Getting Started
Option 215 Limitations
3.1999 GHz, and so on. This operation is normally not visible because
you have so many trace buckets. However, it does have an effect on the
behavior of Option 215 External Source Control at the limits of its
frequency ranges.
Option 215 External Source Control requires a 'spare' bucket at the
beginning and at the end of every sweep on the signal source. In other
words, to make the 1.0 GHz sweep from 3.0 GHz to 4.0 GHz in the
example above, one 'spare' bucket is required at the start to 'catch' the
data between 2.9000 GHz and 2.9999 GHz, and similarly, another
'spare' bucket is required at the end of the sweep.
This means that the number of sweep points on the signal source is
always two higher than that specified on the PSA Series analyzer to
allow for these 'spare' buckets.
You need to remember this frequency range limitation when setting up
your Option 215 measurements. Continuing with the 3.0 GHz to
4.0 GHz example sweep above, a problem arises if your signal source
has a maximum frequency of 4.0 GHz. The source can not sweep beyond
4.0 GHz, so the frequency range of the 'spare' bucket at the end of the
sweep must fall completely below the 4.0 GHz upper limit of the signal
source. This 'spare' bucket therefore 'catches' data from 3.9001 GHz to
4.0000 GHz. The previous bucket (3.8001 GHz to 3.9000 GHz)
represents the last bucket actually used in the sweep, so in this
example, the maximum frequency that your 4.0 GHz signal source
could sweep would actually be 3.9 GHz.
In other words, you can never quite reach the full frequency range of
your signal source. How close to the limit you can get depends on the
size of your buckets. This is determined by the number of sweep points
and the range over which you are sweeping. The more sweep points you
use, and the smaller the range of the sweep, the smaller will be the size
of the buckets. Therefore, the closer you will be able to get to the
frequency limits of your signal source. You can approach, but never
quite meet, the frequency limits of your source.

Frequency Calculation Examples

See the Hints and Tips Chapter for examples of frequency settings that
TIP
will not work because you are either exceeding the frequency range of
your signal source or the frequency band of your spectrum analyzer.

Example 1: A Simple Sweep

Suppose that you specify on your PSA Series analyzer that you wish to
sweep from 2.85 GHz to 3.0 GHz using 601 points. What is the actual
range that the signal source will sweep?
First, we need to work out our bucket size, or the bucket width. This is
given by the range in Hertz divided by (number of points minus 1), or
10 Chapter 1