Instrument Control Toolbox

Creating and Downloading an Arbitrary Waveform to a Function Generator

This example shows how to use the Quick-Control Function Generator to generate arbitrary waveforms.

Instrument Control Toolbox™ supports communication with instruments through interfaces and drivers. For a complete list of supported hardware, visit the Instrument Control Toolbox product page at www.mathworks.com/products/instrument

Introduction

In this example we will create and download an arbitrary waveform to an arbitrary waveform generator using Quick-Control Function Generator.

Requirements

To run this example you need:

  • An arbitrary waveform generator (This example uses Tektronix® AFG3022B).

  • VISA software installed on your machine (This example uses Agilent® IO Libraries Version 16.1).

  • IVI-C drivers for the instruments installed on your machine (This example uses Tektronix® tkafg3k IVI-C driver version 3.2 from the IVI Foundation Driver Registry).

  • Instrument Control Toolbox™.

Define waveform parameters

We will create an arbitrary waveform that consists of three different waveforms. Each waveform's properties, including the amplitude and frequency,will be set in the section below. For each waveform, the amplitude is in volts, while the frequency in Hz.

When generating signals for a function generator it is important to ensure continuity in the time domain so as to not introduce unintended spectral content in the signal, especially if the waveform is going to be played back repeatedly. To ensure continuity you can define the time vector such that it contains an integral number of cycles of each of the three tones that will compose the synthesized waveform.

timeStep = 0.001;
time = 0:timeStep:(1-timeStep);

Parameters for the first waveform

amplitude1 = 0.2;
frequency1 = 10;

Parameters for the second waveform

amplitude2 = 0.8;
frequency2 = 14;

Parameters for the third waveform

amplitude3 = 0.6;
frequency3 = 18;

Create arbitrary waveform

We will create our three individual waveforms using the sin command.

waveform1 = amplitude1*sin(2*pi*frequency1*time);
waveform2 = amplitude2*sin(2*pi*frequency2*time);
waveform3 = amplitude3*sin(2*pi*frequency3*time);

The arbitrary waveform will be a combination of each of the above listed waveforms.

waveform = waveform1 + waveform2 + waveform3;

Add random noise to the waveform created earlier.

waveform = waveform + 0.3*rand(1,size(waveform,2));

Some function generators require a normalized waveform. In this case the waveform is normalized between -1 to +1.

waveformArray = (waveform./max(waveform))';
plot(waveformArray);
xlabel('Samples');
ylabel('Amplitude');

Connect to function generator

Now that you have your waveform you need to download it onto the function generator. You will use the Quick-Control Function Generator or fgen function of the Instrument Control Toolbox™ to do so.

f = fgen;

Discover all the available instrument resources (targets) you can connect to, using the getResources command.

getResources(f)
ans =

 ASRL1::INSTR
 GPIB0::4::INSTR
 GPIB0::INTFC
 GPIB1::INTFC
 PXI0::MEMACC
 TCPIP0::172.31.57.64::inst0::INSTR
 TCPIP0::a-m6104a-004598.dhcp.mathworks.com::inst0::INSTR
 TCPIP0::a-m7054b-340327::inst0::INSTR
 testresource


Select an instrument you want to communicate with. The resource has to be set before connecting to the instrument.

Because the IP address of the instrument is 172.31.57.64, the Resource property will be set to the following.

f.Resource = 'TCPIP0::172.31.57.64::inst0::INSTR';

Connect to the function generator.

connect(f)

Download the created waveform

Specify the channel of the function generator where the waveform would be generated. Here, the waveform would be generated on channel number 1.

selectChannel(f, '1');

Since you will be generating a custom arbitrary waveform, set the Waveform property to Arb.

f.Waveform = 'Arb';

You are now ready to download the previously generated arbitrary waveform waveformArray to the function generator.

downloadWaveform (f, waveformArray);

Enable the waveform generation.

enableOutput(f);

Clean up

clear f;