3 VMA Mode
3.1 Digital Demod Measurement
Example
:DISP:DDEM:WIND:DATA MTIM
Sets the first window data to IQ Meas Time
:DISP:DDEM:WIND:FORM CONS
Selects Constellation as the first window data format
IQ Ref Time
Available for all modulation formats except 2-FSK.
IQ Ref Time is the reconstructed ideal time waveform to compare IQ Meas Time
against. There are 6 available formats for this trace data: I-Q, Constellation, Real,
Imaginary, I-Eye Q-Eye and Group Delay. Normally this trace data is displayed with
I-Q format.
Format name Description
I-Q Real part of data is shown on horizontal axis, imaginary part is shown on vertical axis, Independent
variable (X axis) is normal to display
Constellation Same as I-Q, but for data with symbols defined, only the symbol points are shown as dots with no
connecting lines
Real (I) Real part of data is shown on a linear Y axis
Imaginary (Q) Imaginary part of data is shown on linear Y axis
I-Eye Real part of data is shown with X axis segmented (generally into 2 symbol segments) and each
segment is overlaid to show signal crossings at symbol boundaries
Q-Eye Same as I-eye but imaginary part of data is shown
Group Delay Shows the derivative of phase response with respect to time
Example
:DISP:DDEM:WIND:DATA RTIM
Sets the first window data to IQ Ref Time
:DISP:DDEM:WIND:FORM CONS
Selects Constellation as the first window data format
IQ Meas Spectrum
Available for all modulation formats except any FSK type.
IQ Meas Spectrum is the frequency spectrum of the IQ Meas Time trace data. The
demodulator produces the spectrum by windowing and FFT the IQ measured data. If
the measured filter is selected, the spectrum represents the signal after filtering.
Example
:DISP:DDEM:WIND:DATA MSP
Sets the first window data to IQ Meas Spectrum
Vector Modulation Analyzer Mode User's &Programmer's Reference 216
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