Hallo,
I am using VSA and matlab to do QPSK and IQ Imbalance things. I opened the measured data (sdf-format) in VSA and resave it as trace and recording in mat-format. Then I loaded those data and ploted them.
However, in trace document the points locate only around the constellation, while in recording document there is a lot of points in the middle. The amplitudes are also different.
In the pic, above is the first 4096 points in the recording, below is the points in trace.
Could anyone help me?
Thanks
Yang Liu
Hello Yang,
When you save a recording, you are "recording time data from your measurement hardware" directly to your disk drive. This means that only time waveform data is saved while saving as a trace will actually includes more data.
When you save a trace, VSA saves the "underlying measurement data for the trace you are saving." This means that traces can also contain "symbol data, summary data, etc." In addition, saving as a trace will look cleaner because it "contains information about how the data was shown in the trace" when it was being displayed on VSA.
Below are references and further reading on this matter:
Saving and Recalling Recordings:
http://rfmw.em.keysight.com/wireless/helpfiles/89600b/webhelp/subsystems/sharing/content/saving_and_recalling_recordings.htm
Saving and Recalling Traces:
http://rfmw.em.keysight.com/wireless/helpfiles/89600b/webhelp/subsystems/sharing/content/saving_and_recalling_traces.htm
Data Header Variables:
http://rfmw.em.keysight.com/wireless/helpfiles/89600b/webhelp/subsystems/sharing/content/data_header.htm