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PCI combo card generates spectrally pure mixed-signals

Posted: 02 May 2005 ?? ?Print Version ?Bookmark and Share

Keywords:ztec instruments? oscilloscope? digitizer? zt530pci?

If you need to create unique analog waveforms with high spectral purity, check out ZTEC Instruments' latest wares, keeping in mind that this is an instrument company that focuses on modular oscilloscopes and digitizers. Its products provide common bench-top instrument capabilities in modular instrument form-factors (including plug-ins for PCI, CompactPCI/PXI and VXI buses).

The new ZT530PCI is a case in point. It's a single-width 3U-sized PCI instrument that combines the functions of an ARB (arbitrary waveform generator) and a function generator. Icing the cake, it can also operate as a high-speed digital pattern generator. Just look at its block diagram to get a flavor of the card's level of integration that makes that all possible.

In operation, you even get canned waveforms, with a library that contains files for DC, sine, square, triangle, pulse, and ramp signal generation. The library also contains noise signals, multi-tone, AM, FM, digital patterns, and arbitrary waveforms.

Custom and canned waveshapes
As you can see, the ZT530PCI is capable of generating a variety of signal types. Of course, you can define your own wave shapes, too. The instrument does that over a wide dynamic range and with low noise.

Indeed, spectral purity is rated (for 10dBm output) at -35dBc for harmonic energy, and -50dBc non-harmonic. At 20dBm levels, harmonic energy is at -30dBc, and -45dBc for non-harmonic. That's just the ticket if you're working with video systems, or today's communications system IF strips (intermediate frequency), for example.

As mentioned in ZTEC's press release (on the left), this card comprises a dual-channel instrument, with both channels operational simultaneously. The press statement refers to the two 16-bit channels operating at 400MS/s.

Interpolation filtering
A digital interpolating filter enables the card's DAC (digital-to-analog converter) to run at rates of up to eight times the data input. That attribute improves harmonic rejection and image rejection in RF applications. So, the card actually provides a 160MS/s data rate with 2x, 4x, and 8x interpolation filter for up to 400Ms/s operation.

Regardless of its on-card approach to generating signal, you get waveforms with 16 bits of vertical resolution. That yields signal levels extending from just 10-mV (p-p) to as high as 20V (p-p) full scale, into a high-Z load (10mV to 10V into 50-ohm loads). You'll also enjoy nine digits of low phase-noise frequency resolution.

Additionally, the ZT530PCI can handle up to a 2-Msample record length/channel. You can also leverage a host of triggering, sequencing, and segmenting capabilities. That, along with its built-in function generator capabilities, gives you a way to generate an even richer variety of waveforms. In addition, the digital TTL outputs provide time markers, sync, or pattern stimuli.

Sequencer Tricks
As for the card's sequencing, it lets the card's deep memory be segmented into multiple smaller waveforms. These can then be strung together, and repeated, in user-defined sequences. Moreover, multiple waveforms can also be loaded into the instrument and then recalled.

Waveform generation can also be started on a trigger event, or be delayed for a specified time from a trigger. The card's trigger input can also be used to gate an output-waveform sequence. With that, waveforms can be generated once, or looped continuously.

Waveform segment sequencing can be sync'd to a trigger event or be permitted to advance automatically. Waveform segments can also be played back seamlessly in any order, and can be repeated up to 65,536 times before advancing to another segment.

The card can also readily generate differential waveforms. In use, its paired analog signals exhibit low channel-to-channel skew. That's what's needed for differential or IQ (in-phase and quadrature) signal generation.

Control flexibility
ZTEC's notes refer to the fact that the product is shipped with plug-and-play drivers that can be used with National Instruments LabVIEW and LabWindows. Not said is that you can control the card through the command interface or through register-level access. The register-level access supports high-speed data transfers, as well as another way to integrate one or more of these plug-ins into a non-standard operating environment.

- Alex Mendelsohn
eeProductCenter




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