Generating a test signal was once as simple as tuning a source to the desired output frequency. But as communications and radar systems have evolved, creating appropriate test signals is no longer so routine. A test source such as an arbitrary waveform generator (AWG) provides the flexibility to create exotic signals, but most AWGs are limited in either bandwidth or bit resolution by their digital-to-analog converters (DACs). For that reason, when developing their model M8190A AWG, Agilent Technologies chose to design and fabricate their own DAC, based on silicon germanium (SiGe) BiCMOS technology. The result is the industry’s most powerful AWG, capable of producing signals with complex modulation and bandwidths to 5 GHz.

The model M8190A is built into an AXIe module, an open standard for modular instrumentation. A single M8190A AWG can fit into a two-slot AXIe chassis (Fig. 1), or a pair of the AWGs can be mounted in a five-slot AXIe chassis together with a controller. The M8190A’s performance owes to a proprietary DAC developed by Agilent Laboratories, the firm’s in-house research facility. The DAC can achieve 14-b resolution at 8 GSamples/s and 12-b resolution at 12 GSamples/s. With 14-b resolution, the DAC delivers as much as -80 dBc spurious-free dynamic range (SFDR).

Because the model M8190A AWG is based on a modular architecture, it can be supplied in any number of formats, such as with one or two channels, with more or less sampling memory, and with a choice of output amplifiers. For example, the instrument can supply direct outputs from the DAC, ideal for generating in-phase/quadrature (I/Q) signals with optimum SFDR at typical analog bandwidth to 5 GHz. The amplitudes of these differential signals can be set from 350 to 700 mV peak to peak with 50-ps 20-to-80% transition time. As an option, the model M8190A can be fitted with additional AC and DC output amplifiers. The AC amplifier, which also delivers a typically 5-GHz bandwidth, is suitable for generating wideband single-ended intermediate-frequency (IF) and RF signals from -10 to +10 dBm with 0.5-dB resolution and 0.3-dB accuracy. Such signals are commonly found in modern radar and satellite-communications (satcom) systems.

The DC amplifier, which is designed to aid in creating signals for low-jitter, time-domain measurements, provides differential output signals with amplitudes from 600 to 1200 mV peak to peak and 20 to 80% transition time of about 35 ps. It supports an output voltage window of about -1.0 to +3.0 VDC for serial bus testing at rates to about 3 Gb/s. This capability of generating multilevel, low-jitter signals equips the M8290A for accurate intersymbol-interference (ISI) testing. According to Jurgen Beck, General Manager of Agilent’s digital and photonic test business, “The M8190A AWG allows engineers to approach reality when they create test scenarios. Because the M8190A simultaneously offers greater fidelity, high resolution, and wide bandwidth, customers can create signal scenarios that push their designs to the limit.”

The model M8190A AWG is equipped with standard memory of 128 MSamples per channel, but can be upgraded to over 2 GSamples of memory per channel as an option. The large memory makes it possible to store multiple signal scenarios or sequences (Fig. 2), and switch between sequences by direct memory access. The AWG is equipped with a 100-MHz clock reference source with stability of ±2 ppm and aging rate of ±1 ppm/year, and can also work with external reference clocks from 1 to 200 MHz. The AWG supports the 64-b Windows 7 operating system from Microsoft (www.microsoft.com), and allows operators to define as many as 256,000 waveform sequences in a sequencer table, as well as store up to 64 signal scenarios. A scenario can be looped as many as four billion times to recreate the most complex analog and digital signal formats.