Arbitrary waveform generator
An arbitrary waveform generator, arbitrary function generator or simply " Arb-Generator " (English Arbitrary waveform generator, AWG ) is a function generator that can generate arbitrarily shaped output signals. Arbitrary waveform generators are used in research, development and service for circuit design and optimization, as well as for audit purposes, as well as troubleshooting.
Construction
Arbitrary waveform generators work on the principle of the direct digital synthesis. The desired waveform is stored in a semiconductor memory whose memory locations are accessed cyclically by a variable frequency in the address generator. A digital -to-analog converter with a subsequent low pass filter and amplifier output generated from the numerical values of the output signal. A central microprocessor controls all functions of the generator and allows keyboard and display, but also interfaces to computer systems (for example, GPIB or USB) programming the device.
The properties of an arbitrary waveform generator are essentially determined by its sampling frequency. According to the sampling theorem, the highest occurring in the output signal frequency ( component ) maximum reach half the sampling frequency, practically by the finite steepness of the anti- aliasing filter but a little less. The word width (in bits) of the latch and D / A converter determines the achievable signal -to-noise ratio and thus the achievable signal complexity. Good standard equipment now offer sampling rates of 50 MHz and signal frequencies up to 20 MHz at 14 -bit resolution and at least 64K ( 65,536 ) words memory depth. Devices achieve peak signal frequencies of 500 MHz at 15-bit resolution and 16 mega samples memory depth.
By digital synthesis and very slow signals can be generated. The signal distortion is mainly determined by the quality of the D / A converter and therefore is generally much lower than with normal function generators, however, the spectral purity of specific sine and RF generators is not achieved.
Application
Arbitrary be used as a universal source in the development, research, testing, and service area. Due to the programmability, a Arbitrary Waveform replace several separate, specific device. The basic functions of a function generator ( sine, Dreieck/Sägezahn- and square / pulse signal ) can be downloaded directly from manually operated devices normally. Also, amplitude or frequency modulated signals as well as variants of these " bursts " (packets of oscillations with breaks in between) are just programmable, calculated in each case, the built-in microprocessor, the desired waveform and stores it in memory. However, there are also arbitrary waveform generators, which are controlled solely by external computers and offer no manual controls.
More complex signals may be calculated on the external computer with special programs and loaded via an interface to the generator. So for example it is possible to superimpose a useful signal with defined interference and noise, fading to simulate etc. Such test signals ( modem and other ) used for example in the examination of data communications equipment. And cut-outs of digital signals such as a serial data transmission can be generated in this way.
The to be generated waveforms may, but need not be produced synthetically. You can also load detected by measurement real-world signals in the arbitrary waveform generator and recalled at any time to work with "real" signals, even when the corresponding experimental setup or test subject is not available, for example in medical applications.
In the industrial environment can detect the input signal of interest with a transient recorder or storage oscilloscope and electronically transmit ( for example via e -mail) to the plant manufacturer who can then adjust with the help of an arbitrary waveform of the facts in the laboratory, for example, a service technician with errors in a system.