Importing and Plotting Constellation Data

A constellation measurement is performed on a symbol, which has been modulated using a digital modulation technique (such as quadrature amplitude modulation). Based on the modulation technique, the symbols are sent across two different carriers. These values are often represented as complex numbers and plotted on two axes (typically the I-axis and Q-axis). In addition, each modulation technique has some number of ideal points where signals are detected at the configured sampling time. These measurements can help identify different types of noise or corruption in these complex signals.

In the KS6800A PathWave Measurement Analytics software, each measurement definition is allocated a set of centers, which represent the ideal points of the measurement. Also, a valid distance is assigned to each measurement, which indicates the farthest drift of a measurement value from the ideal center, before it can be termed as being out of limits. Each measurement consists of one or more points that have been sampled and the measurement will be out of limits if any of its points are beyond the valid distance of an expected constellation center.

  1. To plot Constellation Diagrams on the KS6800A PathWave Measurement Analytics software, you may either generate a JSON file programmatically on your local machine or import a Dataset JSON file available on a remote interface containing information about Constellation Diagrams. See Import JSON Data for more information.
  2. To view the Constellation Diagrams that have been imported to a Dataset, see Selecting Fields to View Charts.
  • Consider the Constellation Diagram plotted below:

The characteristics of the Constellation chart are:

  1. The symbols of the constellation are plotted on two axes, namely the I-axis and Q-axis. The I-axis corresponds to the horizontal scale (X-axis) and the Q-axis corresponds to the vertical scale (Y-axis).
  2. Hovering the mouse cursor over each dot shows the value of each plotted symbol in the format <value on I-axis> : <value on Q-axis>.
  3. Each red-dashed circle represents the valid distance assigned to each measurement in the Constellation, which is the farthest drift that a value can attain from its center.
  4. The KS6800A software does not plot multiple charts in the same instance as the Constellation Diagram is plotted.
  5. You may perform one or more of the following actions with respect to the Constellation Diagrams:
    • Export all Constellation Diagrams using the Download JSON Data feature. The target is saved as a JSON file.
    • Split the Constellation Diagrams with the SPLIT feature. See Splitting Plotted Graphs for more information.
    • Modify the scaling on Constellation plots. See Fine-tuning Charts for more information.
    • Remove the Constellation plots. See Deleting Charts for more infromation.
    • Generate Shareable link or Curl / Powershell scripts. See Sharing Plotted Data for more information.