About State Definitions (Digital Demod)

A "state definitions" file is used by "Digital Demod" analysis to define the constellation symbol states for various digital modulation formats. One State Definitions file contain the constellation symbol state definition for multiple digital modulation formats. The VSA allows you to create and recall a user-defined custom state definitions file. The VSA initializes with the default state definitions file "default.csd".

The VSA provides two properties to recall, load, and view State Definitions files:

Recall State Definitions:

recalls and load digital modulation "state definitions" files (.csd extension) State Definitions files define the current measurement digital modulation constellation state diagram symbol definitions.

View State Definitions:

For select digital modulation formats, the View State Definitions drop-down will show a "state definitions" table for the measurement digital format. The State Definitions table represents a constellation (state) diagram with symbol bit definitions for each state.

Not all digital modulation formats support viewable state definition tables. The View State Definitions table is blank for non-supported digital formats.

The following digital format do not support custom state symbol bit definitions: pi/4 DQPSK Differential Quadrature Phase Shift Keying: QPSK modulation using differential encoding of the digital information stream., MSK Minimum Shift Keying, DVB QAM Quadrature Amplitude Modulation, StarQAM, and CPM Continuous Phase Modulation (FM Frequency Modulation).
Legacy State Definition files: State definition files that were created for the Keysight 89400B VSA can be recalled and loaded into the 89600 VSA. State definition parameters that are unique to the 89400B VSA (such as sync patterns) are not used by the 89600 VSA.

State Definitions File

The best way learn about State Definitions files is to open and use the VSA default State Definitions file "default.csd" as a tutorial. The default file is located in one of the following folders depending on the operating system:
%PROGRAMFILES%\Keysight\89600 Software <ReleaseVersion>\89600 VSA Software\Data\Default.csd.

The default.csd file is an ASCII comma separated delimited text file that can be viewed and edited in any ASCII text editor program.

The VSA default.csd state definitions file contains the default symbol state definitions for all of the digital modulation formats that can be customized. The file also contains information and comments that will help you create a custom state definition file including;

state definitions tables for each supported digital format,
procedural instructions describing how to create a new custom file, and
the correct symbol state syntax that must be followed for each digital modulation format

Example State Definitions

The first example defines each state for the 16-QAM modulation format. The rows and columns correspond to the rows and columns in the 16 QAM constellation diagram.

!# Example: State definitions for 16-QAM

! "S_16QAM_1","0011","0010","0001","0000"

! "S_16QAM_2","0111","0110","0101","0100"

! "S_16QAM_3","1011","1010","1001","1000"

! "S_16QAM_4","1111","1110","1101","1100"

The second example defines each state for the 4-FSK Frequency Shift Keying: A form of modulation using multiple carrier frequencies to carry the digital information. The most common is the two frequency FSK system using the two frequencies to carry the binary ones and zeros. modulation format. Note that S_4FSK_1 corresponds to the right-most point in the constellation diagram and S_4FSK_4 to the left-most point.

!# Example: State definitions for 4-FSK

! "S_4FSK_1","00"

! "S_4FSK_2","01"

! "S_4FSK_3","11"

! "S_4FSK_4","10"

Creating a Custom State Definitions Table

Use the VSA default.csd state definitions file as template to create a custom state definitions file from. Only those digital modulation formats contain ed in the default.csd can be modified.

First make a copy of the original default.csd to create your new custom.csd file from. Do not modify the original default.csd file.
Open the custom.csd file in an ACII text editor. Locate and modify the state definition of the digital format of interest and save.

Make sure to create a copy of default.csd before changing the default state definitions or the 89600 VSA software will have to be re-installed to restore the original default state definitions file.

Using Custom State Definitions File

To Recall and load a State Definitions file, click MeasSetup > Digital Demod Properties > Format > Recall State Definitions and navigate to your custom state definitions folder and select the"custom State Definitions.csd" file.
Next verify that the new state definitions have been correctly loaded, click the View State Definitions drop-down (MeasSetup > Digital Demod Properties > Format > View State Definitions) to view the symbol state definitions.
Verify that the custom state definitions are correctly applied to the current measurement. Open the IQ Meas Time trace to verify the constellation state and open the Sym/Errs trace to verify the symbol data bits.
If the custom state definitions have not been correctly applied to the measurement, close and restart the 89600 VSA application.

The measurement State Definitions will persist until the VSA is preset. To preset the VSA, select Preset All (click File > Preset > Preset Setup or File > Preset > Preset All). Preset All will reset the digital demod format "state definitions" to the default "State Definitions" file (default.csd)values.

Viewing the Current State Definitions

To view the state definitions for the currently selected modulation format, click View State Definitions expand drop-down (MeasSetup > Digital Demod Properties > Format > View State Definitions).