Interactive simulation of communication systems

On this site experiments in the field of communications technology are provided online free for use.

Each experiment uses a specific simulation that is implemented using labAlive. labAlive is a graphical and interactive simulator tool for communications systems. The virtual experiment environment emulates a real-world laboratory.

• Intuitive tool
• Mediator between theory and practice
• Teaching aid

Open measures and system properties

Click on wire	Open measure
Left click on a wire.	Open the default measure, usually oscilloscope.
Right click on a wire.	Select a measure. The set of offered measures depends on the signal type of the wire, e.g. analog, digital, complex signal.

Click on system	Open system properties
Left click on a system box or a bullet representing a generator.
Right click on a system box.	View the transfer function or impulse response of filters.

Measure settings

Click on settings icon	Open measure settings

Click on more details button	Open measure settings details

Menu

Menu	Action
	Pause, continue and control speed of the simulation.
	Modify the setup and restart the simulation.

Keys & shortcuts

Key	Action
Pause	Pause or continue the simulation.
F2	Slow down the simulation speed (50%).
F3	Speed up the simulation speed (200%).
F4	Reset to initial simulation speed.
1	Process one simulation step and then pause.
2	Process 10 simulation steps and then pause.
3	Process 100 simulation steps and then pause.
4	Process 1000 simulation steps and then pause.
5	Process 10000 simulation steps and then pause.
6	Process 100000 simulation steps and then pause.
F8	Show speed slider.
F9	Show simulation status.
F10	Show preferences dialog.
F11	Show simulation settings dialog. (Depends on simulation)
F12	Show simulation setup dialog. (Depends on simulation)

Measures overview

With mylabAlive you can simulate so many different hardware experiments that the range of possibilities are up to yourself. You'll need different measures to see or hear what the simulation is doing.

Each measure is designed for a special field. The best thing is, the instruments would cost a lot in reality, but are free in these simulations.

Oscilloscope - operate and control

The oscilloscope is one of the most important/significant measuring instrument in electronics. This description is designed to give an overview about the measure.

Open oscilloscope

Depending on the simulation, the oscilloscope opens automatically. Alternating open the scope by right-click on the wire and selecting oscilloscope. Left-click on the wire will open the default measure, which is also usually the oscilloscope.

Picture 1: Right-click on wire to open measure selector

In some simulations the scope will start togehter with the control element. Depending on the experiment, the scope may differ in form of the background, beam and grid. To get more informations about these design settings, please visit the Preferences tab.

Picture 2: Oscillosope screen with sine wave

Measure

To measure the amplitude of the signal at a certain time or measure the rising time of a signal to a certain amplitude, mark the signal by clicking at the spot with the left mouse. A fine red-dotted line shows the time and amplitude at the marked spot.

The marked measuringspot will dissappear within the next cycle of the oscilloscope. To prevent this, press Pause on the keyboard to pause the simulation. After the simulation pauses, the measuringspot will stay at the display. To restart the simulation, again press the Pause key.

To delete the marker, double-click with the left mouse on the scope and the marker disappear.

Picture 3: Marker on signal to measure time and amplitude

Open settings

We discussed how to change the design of the scope. If you want to change the amplitude/ division, time/division or shift the signal you can open the settings menu with 2 options.

First method: Right-click on scope

The menu will popup and display all settings (Picture 4).

Second method: Gear symbol

Click on the gear symbol located in the upper right corner of the scope. The ampl/div and time/div settings appear. With the arrow on the right-side (green circle), you can open further adjustments.

Note: You need to click through 2 more stages to get to the full settings menu.

Picture 4: All stages of oscilloscope setting

In picture 4 you can see the settings menu. Declaration of every single setting can be found in table 1.

Table 1: Oscilloscope settings

Settings
AMPL / DIV	Changes the amplitude per division. Affects the y-axis
TIME / DIV	Changes the time per division. Affects the x-axis
Offset	Adds a certain offset of the signal. Affects the y-axis
y min	Shifts the zero-line horizontally.
y-axis shift	Shifts the y-axis vertical.
Draw	Continous Discrete Dirac Sample & hold
Luminiscence	Single beam Luminiscence Eye pattern
Display size	Frame - half 441px Frame - quarter 219px Frame - full 890px Diagram - quarter 219px Diagram - half 441px Diagram - full 890px Print - quarter 477px Print - half 943px Print - full 1906px 604px
Keep Beam	Freezes the the graph

Copy paste signal

The oscilloscope can also show more than one beam at a time. Simply select the window from which you want to copy the
beam and press "Ctrl + C". Change to your desired oscilloscope window and press "Ctrl + V". Now a new colored beam should appear.

Note: If you resize the window only the original signal will remain.

Picture 5: Oscilloscope before copy

Picture 6: Oscilloscope after paste

Other Oscilloscopes

Spectrum analyzer - operate and control

Next to the oscilloscope(put link in here), the spectrum analyzer is an important instrument in the development of circuits. A spectrum analyzer is a piece of electronic equipment that is used to measure the magnitude of an input signal set against the full frequency range of the instrument. The x axis shows the frequency and on the y axis the amplitude/level.

Open spectrum analyzer

Note, whether the simulation automatically opens the spectrum analyzer, you are able to open the measure by right-click on the wire and selecting Spectrum Analyzer

In some simulations the spectrum analyzer will start togehter with the main window. Depending on the experiment, the display may differ in form of the background, beam and grid. To get more informations about the settings, please visit the Preferences tab.

Measure

The spectrum analyzer can be used to measure the amplitude/level at a certain frequency. Mark the frequency with the left mouse button. A fine, red-dotted line shows the frequency and amplitude/level at the marked spot.

To delete the marker, double-click with the left mouse button on the scope. The marker disappear.

Open settings

To change the amplitude/division, time/division or shift the signal open the settings menu with one of the 2 following options.

First method: Right-click on scope

The menu will popup and display all settings (Picture 4).

Second method: Gear symbol

Click on the gear symbol located in the upper right corner of the scope. The ampl/div and time/div settings appear. With the arrow on the right-side (green circle), you can open further adjustments.

Note: You need to click through 2 more stages to get to the full settings menu.

In picture 4 you can see the settings menu. Declaration of every single setting can be found in table 1.

Table 1: Spectrum analyzer settings

Settings
AMPL / DIV	Changes the amplitude per division. Affects the x-axis
FREQ / DIV	Changes the frequency per division. Affects the y-axis
Resolution Bandwidth
Down Sampling
Start Amplitude	Adds/subtracs Divisions
Reference level	Sets the reference level
Center Frequency	Changes the start frequency (Only TransferFunction Spectrum)
Start Frequency	Changes the start frequency
Draw	Continous Discrete Dirac Sample& hold
Spectrum	V(Periodical) V/Hz(Pulse) V²/Hz(Power density) (Transfer Function)
Scale	Linear Log
Averaging	On Off
Fourier Transformation	FFT DFT DFT two-sided
Windowing	Off On
Display size	Frame - half 441px Frame - quarter 219px Frame - full 890px Diagram - quarter 219px Diagram - half 441px Diagram - full 890px Print - quarter 477px Print - half 943px Print - full 1906px 604px
Keep Beam	Freezes the the graph

Copy paste signal

The spectrum analyzer can also show more than one beam at a time. Simply select the window from which you want to copy the
beam and press "Ctrl + C". Change to your desired spectrum analyzer window and press "Ctrl + V". Now a new colored beam should appear.

Note: If you resize the window only the last copied signal will remain in addition to the original signal.

Picture 5: Spectrum analyser before copy

Picture 6: Spectrum analyzer after paste

Other spectrumanalyzer

Small Measures

labAlive provides additional small measures which allows the user to perform a large number of different measurements. Each measure covers a specific field of measurement. This overview is designed to show each measure with an image of the interface, a small introduction and a table with the corresponding code.

To use one of the measure in a simulation, take the code from the corresponding table and paste it into the sourcecode of the simulation.

Multimeter

The multimeter is an electronic measure that combines several measurement functions in one unit. Against the "real" multimeter this one can measure power, average of the signal, PAPR and peak amplitude.

To change the measure function, click on the gear symbol located on the right side of the GUI. Table 1 shows an overview of all functions.

Table 1: Modes of multimeter

Multimeter
Mode	Unit	Description
Power	V²	Normalized electric instantaneous power
Average	V	Arithmetic mean of the signal
Peak-to-average power ratio	dB	PAPR is the peak amplitude squared (peak power) divided by the average power
Peak amplitude	V	Peak amplitude of the signal

The measure can be called in the source code of the simulation. To include this, please consider to take the code out of table 2.

Table 2: Overview of measure and corresponding code

System	Code
Multimeter	multimeter

Power Meter

Picture 2: Power Meter GUI

A power meter ist a electronic measure that measures the amount of electric energy. In this case, the power meter measures the energy of signals in V². This is the only measurement function.

The measure can be called in the source code of the simulation. To include this, please consider to take the code out of table 3

Table 3: Overview of measure and corresponding code

System	Code
Power Meter	powerMeter

Signal viewer

Picture 3: Signal viewer GUI

The signal viewer is a tool which allows the user to see the current value of the signal. This device measures voltages in V and prints the value in a decimal number.

The signal viewer prints the value on the screen. The values can be logged with the signal logging tool.

These measures can be called in the source code of the simulation. To include this, please consider to take the code out of table 4.

Table 4: Overview of measure and corresponding code

System	Code
Signal viewer	signalViewer
Signal logging	signalLogging

Audio player

Picture 4: Audio player GUI

Table 5: Overview of measure and corresponding code

The audio player can be used to play the signal like an audio wave.

These measures can be called in the source code of the simulation. To include this, please consider to take the code out of table 5.

System	Code
Audio player	audioPlayer
Audio Player Stereo	audioPlayerStereo

Constellation diagram

Picture 5: Constellation diagram GUI

A constellation diagram displays the signal as a two-dimensional xy-diagram. The angle of each point represents the phase shift of the carrier wave. Most times this tool is used together with QPSK and PSK applications.

The measure can be called in the source code of the simulation. To include this, please consider to take the code out of table 6.

Table 6: Overview of measure and corresponding code

System	Code
Constellation diagram	constellationDiagram

Signal logging

There is a signal logging function available. It can be used to save samples in multiple file formats. To use it, right click on the connection that you want to log and choose "Signal logging". The following window will open. It shows the current amount of logged samples.

By clicking on the gear symbol on the right of the new window, you can set up the signal logger for proper use. A new window will be opened.