Introduction to the functions and common classifications of signal sources

Function of signal source:

The signal source mainly provides the required known signals (various waveforms) to the circuit under test, and then uses other instruments to measure the parameters of interest. It can be seen that the signal source does not measure any parameters in electronic experiments and test processing, but simulates various test signals according to the user's requirements and provides them to the circuit under test to meet the test needs.

Classification of signal sources:

There are many ways to classify signal sources, one of which is to divide them into mixed signal sources and logic signal sources. Mixed signal sources mainly output analog waveforms; logic signal sources output digital patterns. Mixed signal sources can be divided into function signal generators and arbitrary waveform/function generators. Function signal generators output standard waveforms, such as sine waves, square waves, etc., and arbitrary waveform/function generators output user-defined arbitrary waveforms; logic signal generators can be divided into pulse signal generators and pattern generators. Pulse signal generators drive a smaller number of square waves or pulse waves to output, and pattern generators generate digital patterns for many channels. For example, the AFG3000 series produced by Tektronix includes the functions of function signal generators, arbitrary waveform/function signal generators, and pulse signal generators.

In addition, signal sources can also be classified according to the type of output signal, such as RF signal generator, sweep signal generator, frequency synthesizer, noise signal generator, pulse signal generator, etc. Signal sources can also be classified according to the frequency band used, and signal sources in different frequency bands correspond to different application fields.

Below, Antai Test will briefly introduce the function signal generator and arbitrary waveform/function generator:

1. Function signal generator

Function generator is the most widely used general signal source, providing waveforms such as sine wave, sawtooth wave, square wave, pulse wave, etc. Some also have modulation and scanning functions.

Function waveform generators are divided into analog and digital synthesis types in design. As we all know, digital synthesis function signal source (DDS) is superior to analog in terms of frequency, amplitude and even signal-to-noise ratio (S/N). Its phase-locked loop (PLL) design allows the output signal to be not only accurate in frequency, but also to achieve a fairly stable state in terms of phase jitter and frequency drift. However, in digital signal sources, the interference between digital circuits and analog circuits is always difficult to overcome effectively, which also results in the output of small signals being inferior to analog function signal generators. Most function signal generators on the market today are DDS signal sources.

2. Arbitrary Waveform Generator

Arbitrary waveform generator is a special signal source that not only has the ability to generate waveforms like general signal sources, but can also simulate arbitrary waveforms required in actual circuit testing. In the operation of our actual circuits, due to the existence of various interferences and responses, actual circuits often have various defective signals and transient signals. If these situations are not considered at the beginning of the design, some will have disastrous consequences. Arbitrary wave generators can help you complete experiments, simulate actual circuits, and conduct comprehensive tests on your designs.

Since arbitrary waveform generation often relies on computer communication to output waveform data. In computer transmission, waveforms are generated through dedicated waveform editing software, which is conducive to expanding the capabilities of the instrument and further simulating experiments. In addition, a certain amount of non-volatile memory is built in, and waveforms can be randomly accessed and edited, which is conducive to reference comparison, or transmitted to the computer through random interface communication for further analysis and processing. Some arbitrary waveform generators have a waveform download function. When doing some experiments that are troublesome, expensive or risky, the waveform can be recorded in real time through instruments such as digital oscilloscopes, and then transmitted to the signal source through the computer interface, and directly downloaded to the designed circuit for further experimental verification.