Keysight E6680A - Fast (Deep) Capture

3 IQ Analyzer (Basic) Mode
3.4 Fast (Deep) Capture
3.4 Fast (Deep) Capture
Fast capture/transfer of large amounts of IQ data is supported over SCPI. To do this,
first set up the desired measurement range, center frequency, span, triggering, and
so on. Use a time length that is convenient for setting up the measurement. The
time length for the captured data is set indirectly as shown below.
A typical SCPI sequence to perform a capture is:
Command Description
:FCAP:LENG
<num_samples>
Sets the length for the next capture in samples. The sample rate is proportional
to the current span, and can be determined via:
Complex spectrum measurement
:SPEC:SRAT?
Waveform measurement
:WAV:SRAT?
To get the number of samples needed, multiply the time length desired for the
captured data by this sample rate
:INIT:FCAP
Pauses the current measurement and starts capturing IQ data using the
current setup and trigger conditions. (The instrument front panel display does
not change nor show the captured data)
:FCAP:BLOC
<num_points_
per_read_
block>
To read the captured data via SCPI in blocks, set the read block size using this
command
The maximum read block size is typically less than the total fast capture buffer
size, which can be determined via :FCAP:BLOC? MAX
:FETC:FCAP?
Now you can repeatedly use this query to read successive blocks of data
The returned data is formatted according to the most recent :FORMat
[:DATA] and :FORMat:BORDer settings
A read pointer that indicates the next sample to be transferred is advanced
automatically following each :FETC:FCAP? query. This pointer position can
be read, or manually set via:
:FCAP:POIN?
:FCAP:POIN <read_pointer_position>
The fast capture data can be read as long as you use only the commands to set read
block size and pointer position, or queries that return the state of the current
measurement. The capture data is cleared by any command that changes the
measurement state or initiates a new measurement, or via SCPI device clear or
:ABORt.
The fast capture data word size can be set to either 32 bit or 64 bit via "Fast Capture
Word Length" on page 424 (:FCAP:WLEN). This enables you to trade off precision
against total capture length.
IQ Analyzer Mode User's &Programmer's Reference 422