A signal generator, also known variously as a test signal generator, function generator, tone generator, arbitrary waveform generator, digital pattern generator or frequency generator is an electronic device that generates repeating or non-repeating electronic signals (in either the analog or digital domains). They are generally used in designing, testing, troubleshooting, and repairing electronic or electroacoustic devices; though they often have artistic uses as well.
There are many different types of signal generators, with different purposes and applications (and at varying levels of expense); in general, no device is suitable for all possible applications.
Traditionally, signal generators have been embedded hardware units, but since the age of multimedia-PCs, flexible, programmable software tone generators have also been available.
General purpose signal generators
A function generator is a device which produces simple repetitive
waveforms. Such devices contain an electronic oscillator, a circuit that is capable of creating a repetitive waveform. (Modern devices may use digital signal processingto synthesize waveforms, followed by a digital to analog converter, or DAC, to produce an analog output). The most common waveform is a sine wave, but sawtooth, step (pulse), square, and triangular waveform oscillators are commonly available as are arbitrary waveform generators (AWGs). If the oscillator operates above the audio frequencyrange (>20 kHz), the generator will often include some sort of modulationfunction such as amplitude modulation(AM), frequency modulation(FM), or phase modulation(PM) as well as a second oscillator that provides an audio frequencymodulation waveform.
function generators are typically used in simple electronics repair and design; where they are used to stimulate a circuit under test. A device such as an
oscilloscopeis then used to measure the circuit's output. Function generators vary in the number of outputs they feature, frequency range, frequency accuracy and stability, and several other parameters.
Arbitrary waveform generators
Arbitrary waveform generators, or AWGs, are sophisticated signal generators which allow the user to generate arbitrary waveforms, within published limits of
frequencyrange, accuracy, and output level. Unlike function generators, which are limited to a simple set of waveforms; an AWG allows the user to specify a source waveform in a variety of different ways. AWGs are generally more expensive than function generators, and are often more highly limited in available bandwidth; as a result, they are generally limited to higher-end design and test applications.
Special purpose signal generators
In addition to the above general-purpose devices, there are several classes of signal generators designed for specific applications.
Tone generators and audio generators
A tone generator is a type of signal generator optimized for use in audio and
acousticsapplications. Tone generators typically include sine waves over the audio frequencyrange (20 Hz–20 kHz). Sophisticated tone generators will also include sweep generators (a function which varies the output frequency over a range, in order to make frequency-domain measurements), multitone generators (which output several tones simultaneously, and are used to check for intermodulation distortionand other non-linear effects), and tone bursts (used to measure response to transients). Tone generators are typically used in conjunction with sound level meters, when measuring the acoustics of a room or a sound reproduction system, and/or with oscilloscopes or specialized audio analyzers.
Many tone generators operate in the
digitaldomain, producing output in various digital audio formats such as AES-3, or SPDIF. Such generators may include special signals to stimulate various digital effects and problems, such as clipping, jitter, bit errors; they also often provide ways to manipulate the metadataassociated with digital audio formats.
synthesizeris used for a device that generates audio signals for music, or that uses slightly more intricate methods.
Video signal generators
A video signal generator is a device which outputs predetermined
videoand/or televisionwaveforms, and other signals used to stimulate faults in, or aid in parametric measurements of, television and video systems. There are several different types of video signal generators in widespread use. Regardless of the specific type, the output of a video generator will generally contain synchronizationsignals appropriate for television, including horizontal and vertical sync pulses (in analog) or sync words (in digital). Generators of "composite" video signals (such as NTSCand PAL) will also include a colorburstsignal as part of the output. Video signal generators are available for a wide variety of applications, and for a wide variety of digital formats; many of these also include audio generation capability (as the audio track is an important part of any video or television program or motion picture).
* [http://rf-microwave.blogspot.com Signal Generators]
* [http://www.signalforge.com/home/sf1/smartlist_11/Application_Notes.html Applications for signal generators]
* [http://www.radio-electronics.com/info/t_and_m/generators/rf-signal-generator-specs-specifications.php Understanding signal generator specifications]
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