What is the function of an arbitrary waveform generator?

Arbitrary waveform generator is the best instrument for simulation experiment. It is a kind of signal source, which has all the characteristics of signal source. We traditionally believe that signal source mainly provides the required known signal (various waveforms) to the circuit under test, and then uses other instruments to measure the parameters of interest. It can be seen that 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.

Arbitrary waveform generator has all the functions of function generator, and can generate basic functions such as sine wave, square wave, triangle wave, etc. In addition, arbitrary waveform generator can also generate analog and digital modulation signals, and support the output of linear/logarithmic sweep frequency signals and pulse trains, which is the biggest feature that distinguishes arbitrary waveform generator from function generator. The full range of function/arbitrary waveform generators can support analog and digital modulation functions such as AM, FM, PM, FSK, ASK, DSB-AM, etc. They all support sweep frequency function and pulse train output function. In these two modes, the trigger source can be selected from internal, external and manual. When internal and manual trigger sources are selected, trigger signal output is supported, which is convenient for trigger synchronization between multiple different instruments.

There are hundreds of applications for arbitrary waveform generators, but in the field of electronic test and measurement, its application scope can basically be divided into three types: inspection, verification, and limit/margin testing. During the debugging stage of the product, engineers need to test various parameters of the product to verify whether the product meets the relevant factory standards. In this process, the arbitrary waveform generator needs to send the signal specified by the standard as the excitation source of the network under test, measure and record the response of the network under test, and then compare the recorded results with the indicators specified in the standard to draw a conclusion of the inspection. In addition, newly developed industrial control modules, data conditioning modules, etc. all need to use arbitrary waveform generators to determine their linearity and monotonicity through exhaustive testing. In many cases, the arbitrary waveform generator needs to add known, repeatable distortion or damage of quantity and type to the signal it provides. By controlling the parameters related to distortion or damage, the limit/margin test of the device under test can be performed.

1. Functions and functions, environment for designers of simulation-based laboratories

Function signal source is the most widely used universal signal source. It can provide waveforms such as sine wave, sawtooth wave, square wave, pulse train, etc. Some of them also have modulation and scanning capabilities. As we all know, in our basic experiments (such as university electronic laboratories, research laboratories of scientific research institutions, factory development laboratories, etc.), we designed a circuit and need to verify its reliability and stability. We need to apply an ideal waveform to it to distinguish the authenticity. For example, we can use the DC compensation function of the signal source to control the DC bias level of the solid-state circuit; for a digital circuit suspected of having a fault, we can use the square wave output of the signal source as the clock of the digital circuit, and use the square wave plus DC compensation to generate a valid logic level analog output, observe the operation of the circuit, and confirm the location of the fault defect. In short, using the basic functions of the arbitrary waveform generator in this regard, you can simulate the signals required for your basic laboratory.

2. Arbitrary waveforms, simulating more complex signal requirements

As we all know, in the operation of the circuits designed in our actual electronic environment, due to the existence of various interferences and responses, the actual circuits often have various signal defects and transient signals, such as over-pulses, spikes, damping transients, frequency mutations, etc. (see 1, 2). If these situations are not taken into account at the beginning of the design, some will have catastrophic consequences. For example, if the over-spike pulse at a in 1 is given to a circuit with poor impact resistance, it may cause the entire device to "burn out". By confirming the degree of sensitivity of the circuit to such a condition, we can avoid unnecessary losses. This requirement is especially important in aerospace, military, railways and some important fields with complex situations.

Due to the special functions of the arbitrary waveform generator, in order to arbitrarily enhance the waveform generation capability, it 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 simulation experiments. At the same time, because editing an arbitrary waveform sometimes takes a lot of time and effort, and each edited waveform may be different, some arbitrary waveform generators have a certain amount of built-in non-volatile memory, which can randomly access edited waveforms, which is conducive to reference comparison; or transmit to the computer through random interface communication for further analysis and processing.

3. Download and transfer, further real-time simulation

In some military, aviation, transportation manufacturing and other fields, the operating environment of some circuits is difficult to estimate. After the experimental design is completed, further experiments are needed in the actual environment. Some experiments are very costly or risky (such as the change of rails during high-speed train experiments, the operation of propellers during aircraft testing, etc.). It is impossible for people to conduct long-term experiments to judge the feasibility and stability of the designed products (such as high-speed trains and airplanes). We can use the waveform download function of some arbitrary waveform generators to record the waveform in real time through instruments such as digital oscilloscopes when doing some cumbersome, costly or risky experiments, and then transmit it to the signal source through a computer interface, and directly download it to the designed circuit for further experimental verification.

In summary, the arbitrary waveform generator is the best tool for electronic engineers to conduct signal simulation experiments. When purchasing, in addition to paying attention to the defects of traditional signal sources - frequency accuracy, frequency stability, amplitude accuracy, and signal distortion, we should also pay attention to its editing and waveform storage and download capabilities, and also pay attention to its output channel number, so as to synchronously compare the phase shift characteristics of two signals and further achieve the simulation experiment state.