Signal Generators includes:
Signal generator basics
A signal generator is piece of test equipment that produces an electrical signal in the form of a wave. This is used as a stimulus for the item being tested.
Signal generators in all their forms are widely used within test and development systems, being used with other test instruments.
When looking at what a signal generator is, it will be seen that they come in many forms - there are many signal generator types, each one being used to provide a different form of signal. Some provide RF signals, others audio signals, some can provide different shapes of waveform and others may provide just pulses.
Signal generators have been used for many years. Early types were very basic by the standard of today’s different types of signal generator. Performance levels as well as the variety of facilities that are available have increased and improved.
Summary of signal generator types
Looking at what a signal generator is, it will be seen that there are many different types of signal generator:
- Arbitrary waveform generator : The arbitrary waveform generator is a type of signal generator that creates very sophisticated waveforms that can be specified by the user. These waveforms can be almost any shape and can be entered in a variety of ways, even extending to specifying points on the waveform.
Essentially an arbitrary waveform generator can be thought of as a very sophisticated function generator.
Being considerably more complex, arbitrary waveform generators are more expensive than function generators, and often their bandwidth is more limited because of the techniques required in generating the signals. . . . . Read more about the Arbitrary Waveform Generator, AWB.
- Audio signal generator: As the name implies this type of signal generator is used for audio applications. Signal generators such as these run over the audio range, typically from about 20 Hz to 20 kHz and more. They are often used in audio measurements of frequency response and for distortion measurements. As a result they must have a very flat response and also very low levels of harmonic distortion.
- Function generator: The function generator is a type of signal generator that is used to generator simple repetitive waveforms. Typically this signal generator type will produce waveforms or functions such as sine waves, sawtooth waveforms, square and triangular waveforms.
Early function generators tended to rely on analogue oscillator circuits that produced the waveforms directly. Modern function generators may use digital signal processing techniques to generate the waveforms digitally and then convert them from the digital into an analogue format.
Many function generators will tend to be limited to lower frequencies as this is where the waveforms created by this type of signal generator are often required. However it is possible for higher frequency versions to be obtained.
- Pulse generator: As the name suggests, the pulse generator is a form of signal generator that creates pulses. These signal generators are often in the form of logic pulse generators that can produce pulses with variable delays and some even offer variable rise and fall times.
- RF signal generator: As the name indicates, this type of signal generator is used to generate RF or radio frequency signals.
An RF signal generator may use a variety of methods to generate the signal. Analogue signal generator types used free running oscillators, although some used frequency locked loop techniques to improve stability. However most RF signal generators use frequency synthesizers to provide the stability and accuracy needed. Both phase locked loop and direct digital synthesis techniques may be used. The RF signal generators often have the capability to add modulation to the waveform. Lower end ones may be able to add AM or FM, but high end RF signal generators may be able to add modulation formats OFDM, CDMA, etc . . so they can be used for testing cellular and wireless systems. . . . . Read more about the RF Signal Generator.
- Vector signal generator: The vector signal generator is a type of RF signal generator that generates RF signals with complex modulation formats such as QPSK, QAM, etc.
The different types of signal generator are able to produce different types of waveform. These can be used in different applications, some testing RF equipment, others providing stimuli for logic boards and others used in a host of different areas to provide the different stimuli needed. When looking at what a signal generator is, it is necessary to determine the type of generator needed for the given job.
More Test Topics:
Analogue Multimeter Digital Multimeter Oscilloscope Signal generators Spectrum analyzer Frequency counter LCR meter / bridge Dip meter, GDO Logic analyzer Power meter (RF & microwave) RF signal generator Logic probe Time domain reflectometer, TDR LabVIEW PXI GPIB / IEEE 488 Boundary scan / JTAG
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