Agilent Spectrum Analysis Basics - Agilent Technologies

Not all digital communication systems are based on well-defined industry
standards. Engineers working on non-standard proprietary systems or the
early stages of proposed industry-standard formats need more flexibility
to analyze vector-modulated signals under varying conditions. This can be
accomplished in two ways. First, modulation analysis personalities are
available on a number of spectrum analyzers. Alternatively, more extensive
analysis can be done with software running on an external computer. For
example, the Agilent 89600 Series vector signal analysis software can be
used with either the ESA or PSA Series spectrum analyzers to provide
flexible vector signal analysis. In this case, the spectrum analyzer acts as
an RF downconverter and digitizer. The software communicates with the
spectrum analyzer over a GPIB or LAN connection and transfers IQ data to
the computer, where it performs the vector signal analysis. Measurement
settings, such as modulation type, symbol rate, filtering, triggering, and record
length, can be varied as necessary for the particular signal being analyzed.
Saving and printing data
After making a measurement, we normally want to keep a record of the
test data. We might simply want to make a quick printout of the instrument
display. Depending on the particular analyzer and printer model, we might
use the parallel, RS-232, or GPIB ports to connect the two units.
Very often, we may want to save measurement data as a file, either in the
spectrum analyzer’s internal memory or on a mass-storage device such as a
floppy disk. In this case, there are several different kinds of data we may
wish to save. This could include:
• An image of the display - Preferably in a popular file format, such as
bitmap, .GIF, or Windows metafile.
• Trace data - Saved as X-Y data pairs representing frequency and amplitude
points on the screen. The number of data pairs can vary. Modern spectrum
analyzers such as the ESA and PSA Series allow you to select the desired
display resolution by setting a minimum of 2 up to a maximum of 8192
display points on the screen. This data format is well suited for transfer
to a spreadsheet program on a computer.
• Instrument state - To keep a record of the spectrum analyzer settings,
such as center frequency, span, reference level, and so on, used in the
measurement. This is useful when documenting test setups used for
making measurements. Consistent test setups are essential for maintaining
repeatable measurements over time.
Most Agilent spectrum analyzers come with a copy of Agilent’s IntuiLink
software. This software lets you transfer instrument settings and trace data
directly to a Microsoft® Excel spreadsheet or Word document.
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