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test&measurementZONE Products for the week of May 12, 2008
Geotest-Marvin SAYS ...
Arbitrary Waveform Function Generator
Geotest-Marvin Test Systems, Inc., a Marvin Group Company, announced the addition of the GX1110, a high performance, single-channel PXI signal generator that offers both arbitrary waveform and DDS-based function generator capabilities within one instrument.
"The GX1110 offers the features and benefits of a DDS-based function generator and an arbitrary waveform generator within one instrument." said David Manor, Vice President of Hardware Engineering for Geotest.
"With both the function generator and AWG modes of operation, users have the flexibility to address a broad range of applications including signal distortion simulation and baseband audio test. When combined with our new waveform creation software WaveEasy, users have a very capable and useful set of tools for creating and generating arbitrary and periodic waveforms for a variety of applications."
The GX1110 features 2 Msamples of memory, supports a 100 MHz sample rate, and is capable of generating low distortion sine waves up to 30 MHz. The creation of waveforms for the GX1110 is also supported by Geotest's WaveEasy software, which allows users to graphically or programmatically construct waveforms that can then be loaded into the GX1110's memory for playback.
EN-Genius Says…
Geotest-Marvin's single-channel 3U-sized PXI card looks like a viable alternative to dedicated standalone ARBs (arbitrary waveform generators), as well as some PXI plug-in card products. With its reasonably high sample-rate and ample memory, and its 12-bit vertical-resolution DAC, this arbitrary waveform generator and sig-gen combo can deliver signals ranging in peak-to-peak amplitude from as low as 100 mV to as high as 8 V.
 In its DDS (direct digital synthesis) mode, the GX1110 generates signals from as slow as 10 µHz all the way up to 30 MHz, notably with µHz resolution. These signals are generated with 50-ppm accuracy, but if you need higher accuracy you can optionally order a temperature stabilized crystal reference oscillator.
In use, the plug-in supports a variety of internal and external modulation schemes. You can generate AM (up to 100% modulation from dc to 20 kHz) and FM (with deviation from dc to 20 kHz bandwidth), as well as phase-offset modulation (from 0º - 360º degrees, with a close 0.1º of resolution).
Cost Effectiveness
Yes, there are faster and higher-bandwidth ARBs on the market, some with Gsample/s sampling rates and 15 or more bits of resolution. They're great if you need an ARB that can provide 500 MHz or so of instantaneous analog bandwidth/channel, but it will come at a premium. If your requirements are modest, but still stringent, consider Geotest-Marvin's GX1110 card. It offers accuracy and features that belie its roughly $2000 price tag.
For example, the GX1110 includes the ability to dish up built-in pre-defined waveforms. Wave shapes include sine, triangle, ramp, noise, Gaussian pulse and Sin (x/x) types. The plug-in also gives you many triggering selections. Modes include continuous triggering, triggering by external or software triggered events, gated hold triggering, and burst triggering.
The GX1110 also uses a phase-locked-loop programmable sample clock for its arbitrary waveform generation mode. An on-board crystal oscillator, or an external 10-MHz reference establishes this PLL reference. When in DDS mode, the oscillator provides 100 MHz as a clock for the system's DDS generator and DAC.
These functions and triggering options should go a long way in making this card immediately usable out of the box. The system's sequencer takes over from there, letting you generate complex waveforms that can be used when troubleshooting data encoding schemes, or simulating transients or distortion, or fast video.
Software In Development
 Geotest's press release jumps the gun. It mentions WaveEasy, but there's nothing on the company's Web site about WaveEasy, nor do any of the company's field reps know anything about it. It turns out that Geotest is still polishing prototype code. According to senior product marketing manager Mike Dewey, WaveEasy will eventually be bundled with the GX1110, and he expects the package will be ready for delivery in about six to eight weeks.
Dewey says the Windows-hosted software will let you hand-draw waveforms in a graphical environment, and let you add pre-described functions to a waveform, as well as give the ability to define individual segments of a waveform. You’ll have the ability to free-form draw a waveform in conjunction with a function-based waveform. So, for example, if you have a sinewave but want to simulate a glitch that appears on the waveform periodically, you can add this to the waveform via the free-form drawing tool.
All of this will be accomplished using familiar pull-down menus and a mouse. Dewey points out that WaveEasy will also let you import waveforms from existing waveform dev tools, such as those available from National Instruments. Acceptable file types will include .csv, .txt, .pm, and .hws files (NI format).
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