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How do I select the right signal generator for my application?

Blog Post created by BoonCampbell Employee on Jan 25, 2018

Quick note: We usually post oscilloscope tips and tricks to this blog, but today we want to share with you about another test & measurement tool often used with or alongside scopes.

 

To develop or test your electronic design, you need to stress it beyond its real-world application. This will insure your device will operate flawlessly for your customers. In some cases, you may find real world stimuli, but most of the time you will need to use instrumentation.

 

Figure shows the stimulus test model with instrumentation to simulate real-world application

Figure 1. The stimulus test model

 

The instrumentation needed to develop and test today’s technologies has grown into many signal generator types over the years. The most popular signal generators provided by test and measurement manufacturers are:

  • Function Generators
  • RF Generators
  • Pulse and Pattern Generators
  • Arbitrary Waveform Generators (AWG)

There are many generators types out there, so choose yours wisely.

 

Function generators

These are the most well-known and cost-effective signal generators. But, they can only provide a limited set of waveforms such as sine, square, and triangle. They are designed to be very easy to use for simple waveforms with limited memory. You can also adjust the generator’s frequency, offset and other output variables as well as the types of modulation.

Function generators are a good general-purpose source. Use function generators when you need a stable and repeatable stimulus signal. You can use them in applications requiring only periodic waveforms such as stimulus response testing, filter characterization and clock source simulation. Some of the more modern function generators are even capable of generating simple AWG waveforms.

 

Radio Frequency Signal Generators (RF Signal Generators)

RF signal generators produce continuous wave tones with variable output power levels. RF generator outputs typically range from a few kHz to 6 GHz while microwave signal generators cover from 1 MHz to 20 GHz. Use them to service radio receivers and other RF applications. Keep in mind that there are many types and sub categories of these generators, and Keysight provides solutions from 9 kHz all the way up to 25 GHz.

 

Pulse Generators and Pattern Generators

Pulse generators and pattern generators have an advantage over function generators because the output repetition rate and pulse widths can be varied. Their internal circuits may be digital, analog, or a combination of both in order to create the desired outputs. The benefits of direct digital synthesis yield precise frequencies. Use them when working on digital circuits, whereas you should use a function generator primarily for analog circuits.

 

Arbitrary Waveform Generators (AWGs)

An arbitrary waveform generator (AWG) can create all the repetitive waveforms that the three generators above can provide. Plus, an AWG can provide single shot pulses and interpolate between defined points. This is helpful when you need to create triangular waveforms. By harnessing the power and versatility of an AWG’s digital signal processing techniques, you can create whatever signals you need to fully exercise your device under test. With this flexibility, you can either confirm proper operation or pinpoint faults within your system. Basically, with your AWG you can create custom solutions for a wide range of applications.

 

Image of Keysight M8195A Arbitrary Waveform Generator

Figure 2. M8195A Keysight AWG

 

Below is another view of the diverse generator market :-

Signal sourceCharacteristicsWave shape
RF Signal GeneratorsCW (continuous wave) sinusoidal signals over a broad range of frequencies. Modulation types include amplitude, frequency, phase and pulse modulation. May include the ability to sweep the output frequency over a user-set range for frequency response testing.Sine
Modulated sine
Swept sine
Vector Signal GeneratorsDigitally-modulated RF signals that may use any of a large number of digital modulation formats such as QAM, QPSK, FSK, BPSK, and OFDM.Sine
Modulated sine
Pulse GeneratorsPulse waveforms or square waves. Used for testing digital and pulsed systems.Rectangular pulse
Data or Data Pattern GeneratorsMultiple logic signals (i.e. logic 1s and 0s) used as a stimulus source for functional validation and testing of digital circuits and systems.Rectangular pulse
Function GeneratorsSimple repetitive waveforms like sine wave, saw tooth, step (pulse), square, and triangular. May include a modulation function such as amplitude modulation (AM), frequency modulation (FM), or phase modulation (PM).Sine
Rectangular pulse
Square wave
Triangle
Ramp/saw tooth
Modulated waveforms
Noise
Arbitrary Waveform Generator (AWG)Digitally-based signal source generating any waveform, within published limits of bandwidth, frequency range, accuracy, and output level.All the above

 

Use your AWG to simulate real world stimulus

In many scenarios, you need real-world, non-repetitive stimulus to fully test your product. To do this, you need an AWG. In addition, you want to simulate the real-world signals early in the development cycle and fully test the robustness of your designs. An AWG allows you to do this and catch any intermittent or inherent design issues quickly and efficiently. This results in less revisions and gets products to market quicker.

 

Once the desired waveform is loaded into the AWG’s memory, it can be used to generate an output waveform. You can then adjust your frequency, amplitude, and DC offset and use tools such as triggering, gating, bursts, and modulation to further customize your stimuli. The advanced stimulus created by your AWG allows you to verify product performance limits under worst case conditions. Because of this, the applications for AWGs span virtually all industries.

 

What kind of signal generator do you need? Function, RF, Pulse or AWG? For real-world, non-repetitive stimuli creation, look to a function or arbitrary waveform generator. To fully utilize your AWG, you should have a basic understanding of the instrument's controls, features, and operating modes. To learn more about AWGs, download the “Fundamentals of Arbitrary Waveform Generation” guide.

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