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Dear Colleague,
In recent years the cost of sophisticated signal generators has come down tremendously. Complex signals can now be generated quite affordably, but it is important to select the instrument that fits your particular needs. Here are some suggestions of products that may make your design life even easier!
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Signal Generators generally include basic fixed-menu waveform generators (sine/saw/square), and those with the ability to create arbitrary (custom) waveforms not already in the instrument's internal memory. No-frills analog
Function Generators tend to be less expensive and simpler to operate than
Digital Function Generators, which offer a small built-in library of waveforms, and
Arbitrary Waveform Generators (AWGs) allow users to also create custom waveforms. Also available are RF and microwave signal generators, and digital pattern generators for more dedicated tasks.
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Arbitrary Function Generators
An
Arbitrary Function Generator (AFG) often provides outputs of sine, square, triangle, ramp, pulse, sin(x)/x, Gaussian, half sine, noise, PRBS and DC waveforms to your device under test. Sweep mode generates a frequency that varies between two specified limits. An AWG can simulate complex signals and can be used to stress-test the robustness of a design with addition of noise, overshoot, spikes, dropouts and glitches that a design might encounter. It can often also be used to provide heart waveforms, or replicate signals measured on an oscilloscope. See
https://youtu.be/dQu5Gf8nWzU.
AWGs come with a built-in library of signals such as: sine, square, pulse, ramp, dc, noise, sin x/x, Gaussian, Lorentz, exponential rise, exponential decay, Haversine, cardiac, etc. AWGs can be programmed from a text file or using a built-in AWG editor, allowing you to define complex waveforms.
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Digital Direct Synthesis
Modern AFGs and AWGs generally based on
Direct Digital Synthesis (DDS) which creates waveforms from a fixed-frequency reference clock. The shape of the waveform improves with the number of bits of the instrument: 14-16 bit D/As are now common. A DDS is superior to an analog phase-locked loop design due to the precise, stable reference oscillator. Multiple channels can operate simultaneously to allow accurate phase offsets or frequencies with preset ratios.
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Block Diagram for a Representative DDS System
©allaboutcircuits.com
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Benchtop Scopes with Built-In AFG
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Digital benchtop oscilloscopes often contain a built-in no-frills AFG or a more versatile AWG, but be aware that sometimes this is an optional extra. It may be more cost-effective to buy an external desktop unit with its multitude of features.
PC-based oscilloscopes from Pico Technology contain a function generator that can deliver standard waveforms such as sine, square, triangle etc. but many models also include an AWG with more capabilities. When sweep mode is activated, the PicoScope signal generator produces a frequency that changes smoothly between the selected Start Frequency and Stop Frequency. You can set the Sweep Type to Up (increasing frequency) or Down (decreasing frequency). There are also Up Down and Down Up modes that sweep the frequency alternately up and down. This is very useful when designing filters or amplifiers.
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Siglent SDS1000X-E Series
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Other related instruments include
RF and Microwave Generators with modulation capabilities (AM, FM, Phase and Pulse Modulation) and vector signal generators that produce digital signals for the purpose of testing communications systems (QAM, QPSK, FSK, BPSK and OFDM).
A
Digital Pattern Generator outputs digital data from previously captured data to repeat sequences for test purposes or from data creation software. They can be used to stimulate electronics designs to emulate standard serial or parallel bus transactions or custom digital interfaces for system or device debugging and characterization. DPGs are useful for FPGA, peripheral, and ASIC emulation and stimulation, protocol level testing, setup/hold verification, production test, mixed signal testing, and general digital stimulus.
Pulse Generators can create short digital signals such as high-speed pulses. The BNC Model Model 577 digital delay generator provides multi-channel 250 ps-resolution timing, delaying, gating, pulsing, and synchronizing functions with other many practical modes of operation and features. It provides precise delays and widths with 250 ps resolution for up to 1000 seconds. This is particularly useful where several pulses or gate signals need to be delayed and timed with respect to each other or with a common trigger.
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Video Signal Generators
A
Video Signal Generator
is used in computer monitor and TV testing. Video signals can simulate incoming signals or faults in various formats such as composite video, NTSC and PAL, and HDMI. For instance, the quantumdata 701A Handheld Video Test Generator provides video signal outputs for testing, calibrating, and servicing any type of video display. It delivers high quality DVI, component video, S-video, composite video and RGB monitor signals and includes SD/HD-SDI serial digital video output across a full range of formats, for installing, testing, calibrating and maintaining commercial SD/HD-SDI video systems.
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