What Is a Signal Generator?
A signal generator is a device that generates various signals in a test manner, including function generators.
Signal generators are designed based on digital technology to generate a variety of waveforms.
A signal generator is not necessarily limited to ideal waveforms; some types are capable of generating signals with distorted waveforms or with noise added to the waveform.
A signal generator is available in stand-alone models that can be operated by the device itself or by a PC or smartphone.
Uses of Signal Generators
Signal generators are used for circuit design verification, analysis, and various experiments.
When used as test signals for products, it is necessary to always have standard signal generators available. It is also necessary to calibrate and adjust the output of the signal generators periodically by comparing it to the standard signal generators.
Signal generators generally produce dozens of waveforms, including square waves, rectangular waves, triangular waves, sawtooth waves, and sine waves.
In addition to ideal waveforms, distortions, and noise can be added to create conditions that are even closer to real-world waveforms, contributing to highly accurate design.
Principle of Signal Generators
As mentioned above, signal generators are used to verify a designed circuit or system by simulating a virtual input signal, which is then input into the equipment to detect any defects. Based on the results, the circuit is reviewed again, and the design of the equipment is completed through a cycle of trial and error.
Generally, equipment is designed in units of circuit blocks. When conducting verification after the design of a single circuit block is completed, input signals are required, but at the initial stage of design, there is no circuit to connect to. Therefore, in such cases, verification is performed by generating the necessary signals from signal generators and inputting them into the completed circuit design.
Furthermore, when the design of each circuit block is completed, and the product is assembled, the signals generated by the signal generators are input and tested in the same way. In this process, we verify not only the ideal input signal but also the signal distortion and noise that may occur under the actual user’s operating environment.
As described above, signal generators are used in a wide range of applications, from the early design stages to near completion of the design, and even during production testing.
Signal Generators Type
There are various types of signal generators, but the following two are typical examples.
1. Function Generator
One of the most versatile signal generators is the function generator. Among signal generators, those that can generate arbitrary waveforms with a single signal generator have been developed with the development of digital technology.
Since function generators can simulate any signal, it is possible to debug and adjust the device under test by simulating it with pseudo-signals before field testing. Signal generators for generating radio frequency (RF) digitally modulated waveforms are also widely used for characterizing RF electronic components, along with spectrum analyzers and power meters.
2. Signal Generators for RF Digital Modulation Waveform Generation
Signal generators are also available for generating radio frequency (RF) digitally modulated waveforms for complex modulation waveforms such as 5G and Wi-Fi signals. It is called vector standard signal generators (digital standard signal generator), and this instrument has a built-in I/Q modulator.
Therefore, up-conversion to I/Q modulation schemes such as 1024QAM and QPSK is possible. Combined with an IQ baseband generator, this signal generator can emulate and output most signals within the information bandwidth supported by the communication system.
Other Information on Signal Generators
1. How to Use Signal Generators
Signal generators, along with voltmeters, ammeters, signal analyzers, and power meters, are central to the measurement of electronic circuits. Nowadays, instrument manufacturers provide measurement environments that can generate arbitrary signals for complex modulated digital systems by using them with dedicated software applications on PCs.
In addition to complex, state-of-the-art digital systems, kits for measuring instruments that can easily generate signals are also available for beginners in electronic and electrical circuits. Since these kits do not deal with the latest complex signals, they can be purchased at very reasonable prices through online retailers.
This signal generator kit can output basic sine, triangular, and pulse waveform signals, along with their operating frequencies, at any desired level, making it a very useful device for experimental verification of small electronic circuits, even for beginners in electronic and electrical circuits.
2. Signal Waveform Capture to Circuit Simulators
Recently, some vendors of measuring instruments have built an EDA environment that allows circuit simulation of actual signal waveforms, which is very useful for designers of RF, analog, and digital circuits.
For example, in the past, the effect of RF nonlinear behavior on the distortion of digitally modulated signal waveforms was usually evaluated by inputting the actual modulated waveforms or verified by IMD (intermodulation distortion) behavior and fed back to circuit design.
Now, however, it is possible to incorporate the actual modulation signal waveform itself into RF analog circuits and front-end modules on a circuit simulator and to study the characteristics of communication systems, such as EVM (modulation accuracy), from a circuit design perspective on a simulator.