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An arbitrary waveform generator (AWG) is a piece of
electronic test equipment
Electronic test equipment is used to create signals and capture responses from electronic devices under test (DUTs). In this way, the proper operation of the DUT can be proven or faults in the device can be traced. Use of electronic test equipmen ...
used to generate electrical
waveform
In electronics, acoustics, and related fields, the waveform of a signal is the shape of its graph as a function of time, independent of its time and magnitude scales and of any displacement in time.David Crecraft, David Gorham, ''Electronic ...
s. These waveforms can be either repetitive or single-shot (once only) in which case some kind of triggering source is required (internal or external). The resulting waveforms can be injected into a device under test and analyzed as they progress through it, confirming the proper operation of the device or pinpointing a fault in it.
Unlike
function generator
In electrical engineering, a function generator is usually a piece of electronic test equipment or software used to generate different types of electrical waveforms over a wide range of frequencies. Some of the most common waveforms produced ...
s, AWGs can generate any arbitrarily defined waveshape as their output. The waveform is usually defined as a series of "waypoints" (specific voltage targets occurring at specific times along the waveform) and the AWG can either jump to those levels or use any of several methods to
interpolate
In the mathematical field of numerical analysis, interpolation is a type of estimation, a method of constructing (finding) new data points based on the range of a discrete set of known data points.
In engineering and science, one often has a n ...
between those levels.
For example, a 50%
duty cycle
A duty cycle or power cycle is the fraction of one period in which a signal or system is active. Duty cycle is commonly expressed as a percentage or a ratio. A period is the time it takes for a signal to complete an on-and-off cycle. As a formu ...
square wave
A square wave is a non-sinusoidal periodic waveform in which the amplitude alternates at a steady frequency between fixed minimum and maximum values, with the same duration at minimum and maximum. In an ideal square wave, the transitions b ...
is easily obtained by defining just two points: At t
0, set the output voltage to 100% and at t
50%, set the output voltage back to 0. Set the AWG to jump (not interpolate) between these values and the result is the desired square wave. By comparison, a triangle wave could be produced from the same data simply by setting the AWG to linearly interpolate between these two points.
Because AWGs synthesize the waveforms using
digital signal processing
Digital signal processing (DSP) is the use of digital processing, such as by computers or more specialized digital signal processors, to perform a wide variety of signal processing operations. The digital signals processed in this manner are ...
techniques, their maximum frequency is usually limited to no more than a few
gigahertz
The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that one h ...
. The output connector from the device is usually a
BNC connector
The BNC connector (initialism of "Bayonet Neill–Concelman") is a miniature quick connect/disconnect radio frequency connector used for coaxial cable. It is designed to maintain the same characteristic impedance of the cable, with 50 ohm and ...
and requires a 50 or 75 ohm
termination
Termination may refer to:
Science
*Termination (geomorphology), the period of time of relatively rapid change from cold, glacial conditions to warm interglacial condition
*Termination factor, in genetics, part of the process of transcribing RNA ...
.
AWGs, like most
signal generator
A signal generator is one of a class of electronic devices that generates electrical signals with set properties of amplitude, frequency, and wave shape. These generated signals are used as a stimulus for electronic measurements, typically used i ...
s, may also contain an
attenuator, various means of
modulating the output waveform, and often contain the ability to automatically and repetitively "sweep" the frequency of the output waveform (by means of a
voltage-controlled oscillator
A microwave (12–18GHz) voltage-controlled oscillator
A voltage-controlled oscillator (VCO) is an electronic oscillator whose oscillation frequency is controlled by a voltage input. The applied input voltage determines the instantaneous oscilla ...
) between two operator-determined limits. This capability makes it very easy to evaluate the
frequency response
In signal processing and electronics, the frequency response of a system is the quantitative measure of the magnitude and phase of the output as a function of input frequency. The frequency response is widely used in the design and analysis of sy ...
of a given
electronic circuit
An electronic circuit is composed of individual electronic components, such as resistors, transistors, capacitors, inductors and diodes, connected by conductive wires or traces through which electric current can flow. It is a type of electrical ...
.
Some AWGs also operate as conventional function generators. These can include standard waveforms such as sine, square, ramp, triangle, noise and pulse. Some units include additional built-in waveforms such as exponential rise and fall times, sinx/x, and cardiac. Some AWGs allow users to retrieve waveforms from a number of digital and mixed-signal oscilloscopes. Some AWG's may display a graph of the waveform on their screen - a graph mode. Some AWGs have the ability to output a pattern of words on a multiple-bit connector to simulate data transmission, combining the properties of both AWGs and
digital pattern generator
A digital pattern generator is a piece of electronic test equipment or software used to generate digital electronic stimuli. Digital electronics stimuli are a specific kind of electrical waveform varying between two conventional voltages that corr ...
s.
One feature of
DDS-based arbitrary waveform generators is that their digital nature allows multiple channels to be operated with precisely controlled phase offsets or ratio-related frequencies. This allows the generation of polyphase sine waves, I-Q constellations, or simulation of signals from geared mechanical systems such as jet engines. Complex channel-channel modulations are also possible.
Some AWG models include various detection schemes to adjust output waveforms in real time based on different kind of measurement results obtained for instance by signal demodulation, photon counting or triggering with an oscilloscope. The integration for signal generation and detection helps to minimize feedback times for demanding applications as for example in certain implementations of quantum error correction and quantum teleportation.
See also
*
Digital Pattern Generator
A digital pattern generator is a piece of electronic test equipment or software used to generate digital electronic stimuli. Digital electronics stimuli are a specific kind of electrical waveform varying between two conventional voltages that corr ...
References
External links
*
AWG primerXYZs of Signal Generators
{{DEFAULTSORT:Arbitrary Waveform Generator
Electronic test equipment