Quick start 3: Run an example with pre-configured data panels and graphs

In the following quick start tutorial, we will open an existing example design that includes iterations, data panels, and customized graphs.

1. Launch a new application of SystemLab|Design by double left-clicking on the SystemLab-Design.exe executable file.

2. From the Menu bar, select File/Open project and go to the folder systemlab_design\systemlab_examples\electrical\qpsk_design

3. Select the design project QPSK Design (it will have a suffix “.slb”) and click on the Open button. [The QPSK design example should appear as shown below]

4. Click the Start button (blue triangle) on the Tool bar to start the simulation.

   The simulation will run for 12 iterations and should take 1-2 minutes to complete. During the simulation a waterfall graph viewer (Fig 2) will be instantiated and updated after each iteration (plotting symbol error rate (SER) as a function of signal to noise ratio per symbol (SNR/sym)). After the simulation is complete, you will also see a customized graph that displays the IQ signal space results for the simulation (Fig 3). Both of these types of graphs are commonly used when analyzing higher order digital modulation systems such as quadrature phase shift keying.

Fig 2: Simulation results viewer (SER Results QPSK)

5. Minimize the SER results QPSK graph by selecting the Minimize icon on the upper right corner of the graph viewer.

6. On the Signal space analyzer viewer, hover your mouse over the spin box that is located in the Iterations group box (Fig 3) and left-click a few times to change the Current iteration setting.

   

   Fig 3: Signal space analyzer (customized viewer) for QPSK design

   As the iteration index increases you will notice the improvement in the resolution of the IQ constellations (iteration 12 is shown in Fig 3) - for the simulation we have linked the iteration number value to the signal to noise ratio (see example code in Fig 4), thus reducing the noise loading as the iteration number increases.

   

   Fig 4: Python script code that is used to calculate the SNR per symbol parameter (located in NRZ_Gen_I.py)

   Customized graphs such as these are built from the “systemlab_viewers.py” Python module (located within systemlab_design\syslab_config_files). During the QPSK simulation, instances of these graphing objects are first declared within the functional block script for the “Decision Analyzer”. These graph views are then populated with data results from dictionaries that are built as the simulation progresses.

7. Taking a closer look at the project design space, you will notice that there are three panels (all with a yellow background) on the design that are not connected to any functional blocks. These are called Data panels and are specialized data objects designed to present numerical data originating from any of the functional blocks in your design. For the QPSK design there are data panels for Impairment metrics, Decision Results and BER Results. In the upper right corner of the SystemLab|Design application, you will see a spin box called Iteration (Fig 1). Like the Signal space analyzer, left-click on the spin box to decrease or increase the iteration number.

   As the iteration index changes you will notice that the “Data panel” results are updated accordingly. The logic is the same as for the customized viewers. Python dictionaries are populated with numerical results during each simulation iteration and are accessed by the “Data panel” objects and in turn displayed in the project design space. Data panels can be viewed as “virtual test instruments” and are useful for presenting or highlighting specific results, validating calculations or analyzing performance trends based on changing input conditions.

About Python dictionaries…

Dictionaries are powerful Python composite data types used for managing collections of objects. In the SystemLab|Design architecture they are used frequently, including tracking data results that are associated with an iteration.

They are built using a key-element combination. Duing simulations, dictionaries are populated with a key (the iteration #) and an associated data element (usually a list) that contains signal data arrays, results, parameters, text data, etc. When a specific iteration # is requested, for example when there is a change in the spin box setting for a signal data viewer, the associated data object/list is accessed for processing. Dictionary entries can be grown or shrunk, making it an excellent tool for saving and tracking data when the size of the data collection is not known in advance.

8. In addition to customized graphs and data panels, the sampled signal data for all ports (and iterations) are held in memory for post-simulation analysis. For example, let’s take a look at the output port for the integrate & dump functional block. Hover your mouse over the dark blue port of the I&D (I) functional block and double left-click to access the Electrical signal data analyzer dialog.

9. There’s a lot of sampled data in our simulation so we will take a look at a smaller segment of the simulation data. One way to do this is to use the zoom feature (magnifying glass) located on the navigation tool bar just below the graph. We will use another method by defining the start and end values for the x-axis and y-axis. On the left panel of the Time data tab, enter the numbers “0” and “1e-8” in the respective data fields for Time (min) and Time (max) (these fields are located within the Time axis min/max settings group box). Once these settings have been entered, select the Apply button at the bottom of the group box.

10. Under the Y-axis min/max settings group box, set the Start value and End value to “100” and “-100” and select Apply.

    The graph will be refreshed and should look similar to the plot shown in Fig 5. The Integrate and Dump receiver is called a matched filter in that it is designed to provide the optimum signal to noise ratio condition prior to making a decision on the received sampled symbol data (all received samples for a given symbol period are first added together and then at the last sample point the data is dumped and re-set before starting to integrate the next set of sampled received data - hence the saw tooth look of the received sampled data set). Like the customized viewers, the sampled data for each iteration can be accessed for this port by adjusting the spin box setting of the “Current” data field within the “Iteration” group box.

    Please note that when changing the iteration number, the entire sampled data set will be re-plotted for the specified iteration. To refocus the plotting region (after changing an iteration setting), re-select the “Apply” buttons at the bottom of the “Y-axis min/max settings” and “Time axis min/max settings” group boxes.

Fig 5: Electrical signal data analyzer view for output of I&D (I) - QPSK Design

In this tutorial we have reviewed the iterations feature of SystemLab|Design and how it can be applied towards building customized graphs and displaying performance trends with data panels.

For more information on building customized graphs see How to add a customized graph to a design project