20 Important Arbitrary Waveform Generator Glossary Terms

Arbitrary Waveform Generator

An arbitrary waveform generator, as the name suggests, is an advanced type of device capable of generating waveforms with little restriction. Once you generate this waveform, you can then insert it into a device for testing to confirm whether or not the device is properly testing or to determine specifically what is at fault. Because arbitrary waveform generators are typically on the high-end of the scale as far as expenses are concerned, you will typically only find them used to test high-end equipment.

Amplitude

Simply put, this is the magnitude of a generated waveform. Typically, this waveform magnitude is measured in volts peak to peak—Vp-p, or volts root mean square—Vrms.

DC Offset

This is an adjustable value for DC voltage that is typically added to the signal output. Most waveform generators have a DC offset ability, which you can add to your waveform, and they can usually be used to generate any combination of offset and amplitude within a -5Vdc and +5Vdc window. If your needs exceed that range, you can still use an external power supply to generate the extra offset needed.

Distortion

This is the measurement of the departure of a waveform from a perfect signal, and it is usually used with sine waves. It is also often referred to as THD, or total harmonic distortion. At frequencies up to 100 kHz, a waveform generator will normally have under 0.5 percent distortion.

Fall Time

The polar opposite of the definition of rise time, the fall time is the measurement of time in which a pulse, square wave or similar signal will fall from 90 percent to 10 percent of its height. While these are the standard percentages to use for measuring fall time, other percentages may also be used.

Frequency

Frequency refers to the measurement of the speed at which a repetitive signal will repeat during a certain period of time. This is most frequently measured in Hz, or cycles of seconds.

Frequency Resolution

Frequency resolution is the minimum available change for a signal.

Modulation Bandwidth

When you modulate the phase, frequency or amplitude of the output of a waveform generator with another signal, the modulation bandwidth is the maximum rate possible when using its control voltage.

Noise

Noise is described as the undesired and invalid signals that occur on the output of the arbitrary waveform generator. Certain generators are capable of providing pink, white and Gaussian noise.

Noise Floor

In signal theory, the noise floor is when you measure the signal that is created from all sources of noise within a system.

Peak to Peak

This is one way to express the magnitude of a generated waveform, or amplitude. Specifically, the peak to peak voltage will represent the difference from the two peaks of the waveform—from its maximum peak to its minimum peak.

Periodic Waveform

This is a waveform that repeats its value in regular periods or intervals.

Rise Time

This is the measurement of time in which a pulse, square wave or similar signal will rise from 10 percent to 90 percent of its height. While these are the standard percentages to use for measuring rise time, others can also be used.

Root Mean Square

This is also one way to express the magnitude of a generated waveform, or amplitude, and it typically gives a sense of the size of the waveform. Specifically, the root mean square voltage—commonly abbreviated as RMS—of a periodic waveform is equal to the value of a DC voltage amount that would deliver the same amount of power that the periodic waveform would.

Sine Wave

As the name suggests, this is a type of waveform that is available on most generators, and it will satisfy the following equation: y=A*sin(t). In this formula, y is the output in voltage, A is amplitude and t is time. The shape of this wave will gradually and periodically vary between its minimum and maximum value. The value as far as peak to peak is concerned for a sine wave is shown as 2*A, whereas the RMS amplitude is A/v2.

Spectral Purity

Spectral purity refers specifically to measuring the monochromaticity of a sample, with the purest possible value occurring with very low levels of phase noise, spurs and harmonics.

Sweep

Sweep refers to a repetitive variation of the frequency of the output of a waveform generator between its start frequency and its stop frequency, though modern generators will typically term this as frequency modulation.

Sweep Rate

Sweep rate is the reciprocal of sweep time, or the amount of sweeps that occur in any given amount of time.

Sweep Time

Sweep time is that amount of time in which a full cycle of sweeps occur. This will vary depending on your waveform generator.