25 Common Things You Can Do with an Arbitrary Function Generator

Introduction

An acquisition instrument - usually an oscilloscope or logic analyzer - is probably the first thing that comes to mind when you think about making electronic measurements. But these tools can only make a measurement when they are able to acquire a signal of some kind. And, there are many instances in which no such signal is available unless it is externally provided.

A strain gauge amplifier, for example, does not produce signals; it merely increases the power of the signals it receives from a sensor. Inevitably, it becomes necessary to test the amplifier before it is connected to the circuit that feeds it. In order to use an acquisition instrument to measure the behavior of such devices, you must provide a stimulus signal at the input.

To cite another example, engineers must characterize their emerging designs to ensure that the new hardware meets design specifications across the full range of operating conditions and beyond. This is known as margin or limit testing. It is a measurement task that requires a complete solution - one that can generate signals as well as make measurements.

The signal generator pairs with an acquisition instrument such as an oscilloscope or spectrum analyzer to create a complete measurement solution. In its various configurations, the signal generator can provide stimulus signals in the form of analog waveforms, pulse patterns, modulation, intentional distortion, noise, and more. To make effective design, characterization, or troubleshooting measurements, it is important to consider both elements of the solution.

The arbitrary function generator (AFG) serves a wide range of stimulus needs; in fact, it is the prevailing signal generator architecture in the industry today. If the DUT requires the classic sine and square waveforms (to name a few) and the ability to switch almost instantly between two frequencies, the AFG is the right tool. An additional virtue is the AFG’s low cost, which makes it very attractive for applications that do not require the versatility of an arbitrary waveform generator (AWG).

The AFG offers unique strengths: it produces stable waveforms in standard shapes such as sine, square, pulse, triangle, and others. In addition, it allows users to generate so called arbitrary waveforms with a shape defined by the user. Moreover, AFGs offer a way to modulate the signal from internal or external sources, generate frequency sweeps or output signal bursts.

Waveforms can be created in a variety ways, the choice of which depends upon the information available about the DUT and its input requirements, whether there is a need to add distortion or error signals, and other variables.

An AFG provides users a means to:

Create: Customer-defined signals for circuit stimulus and testing.
Replicate: Synthesize a real-world signal unavailable in the electronics lab (previously captured from an oscilloscope).
Generate: Ideal or stressed reference signals for industry standards with specific tolerances.

Embedded and Semiconductor Test Applications

Clock Source

TYPICAL APPLICATION

Frequency margining: Test clock frequency operating range of digital circuits. Substitute unavailable clock source for functional test of device.

USERS

Electronic test and design engineers who develop embedded and digital communication circuitry.

BENEFITS OF USING AN ARBITRARY FUNCTION GENERATOR

Cost savings over dedicated pulse generators.
Dual channels and floating outputs to generate differential signals.
Pulse and square frequency range up to 160 MHz.

TIPS AND HINTS

Differential clock signals, e.g. for PECL, LVPECL or LVDS, can be generated with a dual channel source with floating single-ended outputs.
To generate a differential signal, configure waveform, frequency and amplitude in Channel 1 and duplicate inverted settings to Channel 2 via the CH1 Complement function on the quick settings menu. Then activate the synchronization mode by setting Frequency CH1=CH2 to On and initiating Align Phase.
Disable any on-board clock source while driving the device with an external clock source.
To avoid signal integrity degradations such as ringing or variable delay and amplitude, take care to obtain adequate impedance matching between the probe connecting to the signal source and the board trace.

LIV curves — * Recommended AFGs: Tektronix AFG31251 / AFG31252.

Characterization of Logic Devices - Timing Margin Test

TYPICAL APPLICATION

Stimulate logic device with data and clock signal to characterize set-up and hold time.

USERS

Electronic design and test engineers who develop or use logic circuits.

BENEFITS OF USING AN ARBITRARY FUNCTION GENERATOR

Dual channels that can easily be synchronized.
Pulse width and delay between channels 1 and 2 adjustable on the fly.
Ease of use and compact form factor.

TIPS AND HINTS

Create two synchronous pulses, one for the clock and one for the data signal, with the data pulse wider than the clock pulse.
Start out with the leading edge of the data pulse placed at the active clock edge, then delay the clock edge versus the data edge until the device output signals that the data is being registered. This is the setup time.
Leave the leading edge of the data pulse in place, and reduce the delay between the trailing edge of the data and the active clock edge (by reducing the data pulse width) until the data is no longer registered. This is the hold time.
Note that setup the and hold times depend on the rise time of data and clock signals, input voltage levels, and operating voltage and temperature. To obtain relevant test results, set these parameters to match normal operating conditions.

Characterize Phase Locked Loop (PLL) Circuits

TYPICAL APPLICATION

Measure bandwidth and jitter transfer of phase locked loop (PLL) circuit.

USERS

Electronic design and test engineers working for:

− Semiconductor companies that develop PLLs.

− Datacommunication equipment manufacturers.

BENEFITS OF USING AN ARBITRARY FUNCTION GENERATOR

Dual channels.
Ease of use.
Compact form factor.

TIPS AND HINTS

Typical Application pulse width modulation to generate clock signals with a precise amount of jitter to stimulate the PLL for measuring its jitter tolerance and jitter transfer function.

Characterizing Operational Amplifiers

TYPICAL APPLICATION

Measure phase shift, gain, overshoot, slew rate performance of operational amplifiers and buffer circuits.

USERS

Electronics design and test engineers working for semiconductor manufacturers developing operational amplifiers.

BENEFITS OF USING AN ARBITRARY FUNCTION GENERATOR

Dual channels and floating outputs to generate differential signals.
Ease of use, compact form factor.

TIPS AND HINTS

To generate a differential signal, configure waveform, frequency and amplitude in Channel 1 and duplicate inverted settings to Channel 2 via the CH1 Complement function. Then activate the synchronization mode by setting Frequency CH1=CH2 to On and initiating Align Phase.
Since operational amplifiers may behave in asymmetrical fashion, i.e., respond differently to a leading versus the trailing edge of an input pulse, the stimulus source should have independently adjustable rise and fall times.

Timing Margin Test of AFE (Analog Front End) for CCD Sensor

TYPICAL APPLICATION

Determine sensitivity of AFE to falling edge time of input signal.

USERS

Electronic design engineers who work on CCD sensor designs at semiconductor and electronics companies that develop digital imaging products.

BENEFITS OF USING AN ARBITRARY FUNCTION GENERATOR

Pulse frequency up to 160 MHz.
Rising and falling pulse edge times adjustable independently.
Waveform parameter adjustments take immediate effect without interrupting test.

TIPS AND HINTS

Set the generator's load impedance setting to match the impedance of the connected circuit so that the amplitude will display accurately.
To isolate the AFE's sensitivity to trailing edge variations, only adjust the trailing edge time and hold the leading edge time constant.

Characterizing CCD Sensor - Delay Margin Test

TYPICAL APPLICATION

Test delay margins of the clock input of the CCD circuit.

USERS

Electronic design engineers who work on designs with CCD sensors at semiconductor and electronics companies that develop digital imaging technology.

BENEFITS OF USING AN ARBITRARY FUNCTION GENERATOR

Square waves up to 160 MHz.
Dual channels that can easily be synchronized.
Fine adjustability of delay between channels 1 and 2.
Convenient short-cut keys for quick access to delay parameter.

TIPS AND HINTS

Activate the synchronization mode of the dual channel signal generator by setting Frequency CH1=CH2 to On and initiating Align Phase.
Determine the delay margin by adjusting the phase delay between clock 1 and clock 2 continuously in fine increments until the circuit stops working properly.

Testing Audio DAC

TYPICAL APPLICATION

Functional test of audio ADC and DAC.
Evaluate clock frequency operating range of audio ADC and DAC.

USERS

Electronic design engineers working in semiconductor companies that design audio ADCs and DACs.

BENEFITS OF USING AN ARBITRARY FUNCTION GENERATOR

Dual channels that can operate with independent timing.
Good noise and jitter specifications.

TIPS AND HINTS

To drive the DAC clock and control the audio generator with a dual channel arbitrary function generator, channels 1 and 2 must run in 'unsynchronized' mode.
Disable any clock source on the DAC test board while driving the device with an external clock source.
Set the generator's load impedance setting to match the impedance of the connected circuit so that the amplitude will display accurately.

Immunity from Power Supply Disturbances

TYPICAL APPLICATION

Evaluate performance and immunity of electronic systems (PC motherboard, automotive electronic device, etc.) to power cycling, transients and disturbances in power supply

USERS

Electronic design engineers designing computers, peripherals, embedded systems, or automotive electronics.

BENEFITS OF USING AN ARBITRARY FUNCTION GENERATOR

Powerful waveform creation and editing capability of ArbBuilder on the unit or ArbExpress software for the PC.
Ease of use and compact form factor of instrument.

TIPS AND HINTS

Configure the generator's load impedance setting to match the impedance of the connected circuit so that the amplitude will display accurately.
If shape of test waveform is prescribed as time and amplitude values, enter them in ArbBuilder or ArbExpress via Point Draw Table.

RF Related Applications

Measure Frequency Response of Bandpass Filter

TYPICAL APPLICATION

Stimulate filter with swept sinewave and measure filter's frequency response with spectrum analyzer.

USERS

Electronic design engineers working for filter vendors or wireless communication equipment vendors.
Professors, lab managers working in student labs and universities.

BENEFITS OF USING AN ARBITRARY FUNCTION GENERATOR

Ease of use.
Large screen shows all relevant waveform and sweep parameters at a single glance for full confidence in correct settings.
Compact form factor leaves more room on the bench for device and cables.

TIPS AND HINTS

If only an oscilloscope is available, and no spectrum analyzer, trigger on the sweep start via the generator's trigger output, set the oscilloscope’s time scale to match the generator's sweep time and interpret it as frequency values.

Measure Intermodulation Distortion of RF Components

TYPICAL APPLICATION

Stimulate RF components with dual tone to measure second and third order intermodulation distortion with a spectrum analyzer.

USERS

Electronic design engineers designing or using RF amplifiers, gain blocks, mixers, modulators, connectors, splitters, couplers, relays, attenuators, PIN diodes, carbon resistors, coaxial cable, and others.

BENEFITS OF USING AN ARBITRARY FUNCTION GENERATOR

Eliminates need for mixer to combine multiple signals.
Ease of use reduces set-up time.
Compact form factor saves room on the bench.

TIPS AND HINTS

Create dual tone conveniently by creating each tone individually in ArbExpress and then adding them via waveform math.
To avoid waveform discontinuities, define both tones with an integer number of waveform cycles.

Pulsed Noise - Figure Measurement

TYPICAL APPLICATION

AFG generates two synchronous pulse signals to power up RF amplifier and trigger noise figure measurement on spectrum analyzer.

USERS

RF design and test engineers developing components and systems for wireless communications for bursttype standards (TDMA, GSM, etc.), as well as radar and electronic warfare.

BENEFITS OF USING AN ARBITRARY FUNCTION GENERATOR

Dual channels that can easily be synchronized.
Ease of use.
Saves cost and bench space compared to dedicated pulse generators.

TIPS AND HINTS

Synchronize the dual channels of the AFG by setting Frequency CH1=CH2 and initiating Align Phase so that the spectrum analyzer measures the amplifier response during the switch on phase.
Match the amplitude in Channel 1 to the bias level of the amplifier.
Match the amplitude in Channel 2 to the trigger input of the spectrum analyzer.

Functional Test of RFID Receiver ICs

TYPICAL APPLICATION

AFG simulates 4 bit RFID pattern and provides trigger signal for functional test of 134.2 kHz RFID receiver ICs.

USERS

Electronic design engineers working in semiconductor companies that design RFID ICs.
Designers of RFID readers.

BENEFITS OF USING AN ARBITRARY FUNCTION GENERATOR

Dual channels that can easily be synchronized to generate RFID signal and synchronous trigger signal.
ArbExpress to define RFID pulses via mathematical formulas.

TIPS AND HINTS

Activate the synchronization mode of the dual channel signal generator by setting Frequency CH1=CH2 to On and initiating Align Phase.
If the RFID pulses are described via mathematical equations, create the waveforms via ArbExpress equation editor.
Set the signal period to match the time duration of the RFID signal.
To test the receiver's sensitivity to frequency variations, adjust the signal period or frequency.
To test the receiver's susceptibility to background noise, use the generator’s Noise Add function.

EMC Radiation Testing

TYPICAL APPLICATION

Measure radiation of ATIS* audio signal inside aircraft.AFG31252 feeds carrier modulated with audio signal from into communication system of aircraft.

USERS

EMC test engineers working for aircraft manufacturers and companies that test aircraft communication systems.

BENEFITS OF USING AN ARBITRARY FUNCTION GENERATOR

Dual channels that can operate with independent timing.
Sine wave frequency range up to 250 MHz.
External modulation capability; compact form factor.
AFG31252 replaces PC playing audio file, audio amplifier and RF generator.

TIPS AND HINTS

Generate the carrier signal with Channel 1 in modulation mode with external source.
Generate the audio signal as arbitrary waveform with Channel 2 and connect it to the modulation input of Channel 1.
To create the waveform file for the audio signal, record it via microphone and oscilloscope, then import it into the arbitrary function generator via ArbExpress.
Set the signal period in Channel 2 to match the time duration of the audio signal.

Characterizing I/Q Modulators

TYPICAL APPLICATION

Measure IQ gain imbalance, quadrature error, frequency response, carrier feed-through, side-band suppression ratio and up-converter losses.

USERS

Electronic design and test engineers working for semiconductor and wireless communication equipment manufacturers.

BENEFITS OF USING AN ARBITRARY FUNCTION GENERATOR

Dual channels that can easily be synchronized.
Phase delay between channels adjustable on the fly, without interrupting the test.
250 MHz sine wave frequency range.

TIPS AND HINTS

Activate the synchronization mode of the dual channel signal generator by setting Frequency CH1=CH2 to On and initiating Align Phase.
Determine gain and phase errors by adjusting amplitude and phase of one channel until undesired sideband power is minimized. The differences in amplitude and phase settings between channels 1 and 2 equal the gain imbalance and quadrature error.

Education-Related Applications

Measure Frequency Response of Bandpass Filter

TYPICAL APPLICATION

Stimulate filter with swept sinewave and measure filter's frequency response with spectrum analyzer.

USERS

Electronic design engineers working for filter vendors and wireless communication equipment vendors.
Professors and lab managers working in student labs in universities.

BENEFITS OF USING AN ARBITRARY FUNCTION GENERATOR

Ease of use.
Large screen shows all relevant waveform and sweep parameters at a single glance for full confidence in correct settings.
Compact form factor leaves more room on the bench for device and cables.

TIPS AND HINTS

If only an oscilloscope is available, and no spectrum analyzer, trigger on the sweep start via the generator's trigger output, set the oscilloscope's time scale to match the generator's sweep time and interpret it as frequency values.

AM/FM Radio Test and Alignment

TYPICAL APPLICATION

Measure IF bandwidth, align RF stage, measure audio bandwidth of FM receiver

USERS

Electronic design engineers working for AM/FM radio manufacturers.
Professors and lab managers working in student labs in universities

BENEFITS OF USING AN ARBITRARY FUNCTION GENERATOR

Ease of use.
Large screen shows all relevant waveform as well as sweep or modulation settings at a single glance for full confidence in correct settings.
Compact form factor leaves more room on the bench for device and cables.

TIPS AND HINTS

Configure the generator's load impedance setting to match the impedance of the connected circuit so that the amplitude will display accurately.

Automotive Applications

Test & Optimization of Engine Control Units

TYPICAL APPLICATION

Simulate various automotive sensor signals, such as pressure, temperature, speed, rotation and angular position for functional test and optimization of engine control units (ECU) for automotive applications.

USERS

Electronic design engineers working in automotive electronics

BENEFITS OF USING AN ARBITRARY FUNCTION GENERATOR

Large display confirms all settings at a single glance.
Amplitude can be entered as Vpp/Offset or as High/Low values.
Powerful waveform creation and editing capability of ArbBuilder and ArbExpress.
To eliminate the need for an eternal amplifier, use the AFG3011C to achieve up to 20 Vpp amplitudes.

TIPS AND HINTS

Activate the synchronization mode of the dual channel signal generator by setting Frequency CH1=CH2 to On and initiating Align Phase.
To synchronize the clocks multiple generators, use one generator as master and connect its Sync Clock output to the Sync Clock inputs of the other generators.
To synchronize multiple generators in phase, set them into Burst - Inf-Cycles mode, and start them simultaneously via an external signal.

Simulation of Automotive Sensor Signals

TYPICAL APPLICATION

Simulate crankshaft, camshaft, wheel, knock and other automotive engine sensor signals.

USERS

Electronic design engineers designing electronic engine control systems for automobiles.

BENEFITS OF USING AN ARBITRARY FUNCTION GENERATOR

Dual channels
Powerful waveform creation and editing capability of ArbBuilder and ArbExpress.
Ease of use and compact form factor of instrument.

TIPS AND HINTS

Activate the synchronization mode of the dual channel signal generator by setting Frequency CH1=CH2 to On and initiating Align Phase.
To create the waveform files, acquire the real-life signal with an oscilloscope, then import it into the arbitrary function generator via ArbExpress.

Characterize and Optimize Power MOSFET Circuitry in Automotive Electronics

TYPICAL APPLICATION

Stimulate Power MOSFET circuitry with pulse signal to measure turn-on and turn-off delay, as well as rise and fall time.

USERS

Electronic design engineers designing motion control, power management, climate control, electronic stability systems, or integrated starter/alternators for automobiles.

BENEFITS OF USING AN ARBITRARY FUNCTION GENERATOR

Built in Double Pulse app for AFG31000 Series reduces test set up time. (For more information on the Double Pulse app see the application note at https://www.tek.com/document/application-note/double-pulse-test-tektronixafg31000-arbitrary-function-generator.)
Compact form factor saves room on the bench.

TIPS AND HINTS

Typical Application the Power Software Package for the MSO5 Oscilloscope to analyze the switching parameters of your power device quickly.

Analyzing Switching Waveforms of IGBT Circuitry

TYPICAL APPLICATION

Measure on and off switching characteristics of IGBT circuitry for ignition coil drives, motor controllers, safetyrelated systems in automobiles, and various industrial applications.

USERS

Electronic design engineers working for:

- Automotive electronics vendors who design motion control, power management, climate control, electronic stability systems, or integrated starter/alternators for automobiles.

- Manufacturers of induction heating and welding equipment

BENEFITS OF USING AN ARBITRARY FUNCTION GENERATOR

Built in Double Pulse app for AFG31000 Series reduces test set up time. (For more information on the Double Pulse app see the application note at https://www.tek.com/document/application-note/double-pulse-test-tektronixafg31000-arbitrary-function-generator.)
Compact form factor saves room on the bench.

TIPS AND HINTS

Set the generator's load impedance setting to match the impedance of the connected circuit so that the amplitude will display accurately.
Typical Application the Power Software Package for the MSO5 Oscilloscope to analyze the switching parameters of your power device quickly.

Medical Applications

Testing Pacemakers, Cardioverter Defibrillators, and other Implantable Medical Devices

TYPICAL APPLICATION

The AFG simulates normal and irregular biomedical signals (e.g. heart fibrillation) for the functional test of medical devices.

USERS

Electronic design and test engineers designing medical devices.

BENEFITS OF USING AN ARBITRARY FUNCTION GENERATOR

Tightly synchronized dual channels.
Floating outputs to generate differential signals.
Instrument's ease of use and compact form factor.

TIPS AND HINTS

Acquire life signal with any Tektronix oscilloscope and convert to AFG waveform via ArbExpress software.
After setting up Channel 1 with desired waveform, frequency and amplitude, duplicate inverse settings to Channel 2 via CH1 Complement function.
Activate the synchronization mode of the dual channel signal generator by setting Frequency CH1=CH2 to On and initiating Align Phase.

Testing Medical Ultrasound Equipment

TYPICAL APPLICATION

Drive ultrasound transducer with sine wave bursts to test medical imaging system.

USERS

Electronic design engineers developing medical ultrasound equipment.
Researchers working in universities engaged in ultrasound research.

BENEFITS OF USING AN ARBITRARY FUNCTION GENERATOR

Ease of use.
Compact form factor.

TIPS AND HINTS

Typical Application the trigger output to trigger the measurement device or imaging system at the beginning of every burst cycle.

Testing Detector Circuit of Medical Ultrasound Equipment

TYPICAL APPLICATION

Simulate ultrasound detector signal to characterize input circuit of medical ultrasound system.

USERS

Electronic design engineers working for medical diagnostic equipment manufacturers.
Researchers working in universities engaged in ultrasound research.

BENEFITS OF USING AN ARBITRARY FUNCTION GENERATOR

Ability to add noise and jitter internally.
Ease of use.
Compact form factor.

TIPS AND HINTS

Add noise internally by activating Noise Add functionin the quick settings menu for Channel 1.
Add jitter internally by operating the instrument in Phase Modulation mode.

Industrial Applications

Characterizing Dynamic Performance of Hydraulic Servo Valves

TYPICAL APPLICATION

AFG stimulates servo valve with square wave to determine actuating time (step response), frequency response (Bode plot) and other specifications for datasheet.

USERS

Electromechanical design engineers involved in design and manufacture of hydraulic servo valves.

BENEFITS OF USING AN ARBITRARY FUNCTION GENERATOR

Ability to generate variety of waveshapes (square, ramp, sine, arb).
>10 Vpp to determine valve characteristics in overdrive.
Ease of use.

TIPS AND HINTS

Set the generator's load impedance setting to match the impedance of the connected circuit so that the amplitude will display accurately.
To drive a device with 0 or 4 to 20 mA input, calculate the corresponding voltage settings for the generator based on the device's input impedance.

Research Applications

Driving and Modulating Laser Diodes

TYPICAL APPLICATION

Drive laser diodes and electro-optical modulators for laser based communication systems.

USERS

Researchers working in universities and research institutes who are involved with optical communication.

BENEFITS OF USING AN ARBITRARY FUNCTION GENERATOR

Dual channels that can operate with independent timing and operating modes.
Arbitrary waveforms up to 125 MHz.
Versatility, ease of use.

TIPS AND HINTS

Set the generator's load impedance setting to match the impedance of the connected circuit so that the amplitude will display accurately.