DSP Blockset

Displaying Signals in the Time-Domain

The Vector Scope block can display both time-domain and frequency-domain data. It differs from the Spectrum Scope in that it does not compute the FFT of inputs.

Example: Displaying Time-Domain Data

In the model below, two frame-based signals are simultaneously displayed on the scope.

To create the model, first load the mtlb signal:

• load mtlb            % Contains variables 'mtlb' and 'Fs'
  

Specify the following parameter values in the Signal From Workspace block:

• Signal = mtlb
• Sample time = 1
• Samples per frame = 16
• Form output after final data value = Cyclic Repetition

Specify the following parameter values in the Digital Filter Design block:

• Filter Type = Lowpass
• Design Method = FIR (Window)
• Filter Order (Specify order) = 22
• Window Specifications (Window) = Hamming
• Frequency Specifications (wc) = 0.25
• Frequency Specifications (Units) = Normalized (0 to 1)
• Magnitude Specifications (Units) = dB

Specify the following parameter values in the Scope properties pane of the Vector Scope block:

• Input domain = Time
• Time display span (number of frames) = 2

When you run the model, the Vector Scope block plots two consecutive frames of each channel at each update. You may want to set the Stop time in the Simulation Parameters dialog box to inf to allow the simulation to run longer. The following section provides a few tips for improving the display.

Improving the Appearance of the Display.   You may want to alter the appearance of the scope display by making some of the following adjustments from the right-click popup menu. To access the right-click menu, click with the right mouse button anywhere in the plot region. These options are also available from the Axes and Channels menus that are visible at the top of the window when Compact display is not selected. You can make all of these changes while the simulation is running:

• Select Autoscale at any time from the right-click menu to rescale the vertical axis to best fit the most recently displayed data.
• Select Compact display from the right-click menu to allow the scope to use all the available space in the window.
• Select CH 1 from the right-click menu, and then select Marker and "o" from the submenus, to mark the data points on the channel 1 signal with circles.
• Select CH 1 from the right-click menu, and then select Color and Blue from the submenus, to code the channel 1 signal with the color blue.
• Select CH 2 from the right-click menu, and then select Marker and Diamond from the submenus, to mark the data points on the channel 2 signal with diamonds.

Viewing Signals

Displaying Signals in the Frequency-Domain