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FPGA-equipped signal processor plays in Windows PCs

Posted: 29 Apr 2005 ?? ?Print Version ?Bookmark and Share

Keywords:gage applied technologies? digitizer? oscilloscope card? signal generator card? compuscope12400?

Gage Applied Technologies' products are part of a rather large family of multi-MHz to GHz digitizers and oscilloscope cards, as well as analog signal generator cards, and digital I/O plug-ins.

With the introduction of this 12-bit dual-channel CompuScope12400 card, also known as the CS12400 digitizer, you can utilize its 200MHz bandwidth to see signals well into the RF range. The CS12400's fast sampling rate also lets you capture signals with very high timing precision.

Scope-like in operation, the CS12400 has both 50-ohm and high-Z inputs. It will accommodate inputs in ranges of 100mV, 200mV, 500mV, 1V and 2V, as well as 5V on the 50-ohm input.

Just drop one of these full-size single-slot cards into a 32-bit 66MHz PCI slot and you'll be all set to get lightning fast 200MBps transfers into your PC's memory, too.

FPGA power

Gage's press statement (on the left) refers to the optionally available FIR (finite impulse response) filtering, and the FPGA-based (field programmable gate array) signal averaging in this product.

The on-board FIR filtering, also implemented in the FPGA, readily removes unwanted noise, letting you see the signal of interest.

By way of contrast, conventional analog filters are typically limited to simpler filtering approaches, such as lowpass, highpass and bandpass filters. Using numerical filtering of waveform data, you can now invoke far more complex filters. You can implement things such as moving-average filters and Gaussian filters.

You can also process input signals through FIR filters with up to 20 taps, and if that's not sufficient, you can actually get 39 symmetric taps using PC software. What's more, your FIR filter coefficients can be tailored to emphasize signal pulses of a specific shape.

Best of all, the FIR filtering is performed in realtime in the FPGA, freeing your PC to handle other tasks; that's parallel processing at its best. Data is filtered during transfers to your host PC, so that the repetitive signal capture rate of the digitizer isn't compromised. This is transparent to Gage's standard CompuScope drivers for Windows. No special software is needed.

Signals buried in noise?

Like the FIR filtering package, Gage's on-board signal averaging is also implemented in an FPGA sub-system. In this case, signal averaging can let you detect low-level repetitive signals. These signals can actually be extracted from a background of high-amplitude noise that might even be higher than the signal of interest.

Like the FIR filters, this capability happens with no host processor overhead, even though waveforms might be averaged at rates greater than 100,000 waveforms/s. In use, the signal averaging gives you maximum waveform lengths of 24,000 samples on two channels, or 48,000 samples on one.

Mathematically speaking, the noise on a signal is reduced by the square root of the number of averages. So, for example, sixteen averages can reduce the noise on a signal by a factor of four. 100 signal averages will reduce the noise by factor of ten.


The system also reduces PCI data traffic by a factor of more than 1,000, giving you an effective processing rate of 800MBps. The maximum number of averages that can be done in one averaging session is 1024, but since the data throughput to your PC has been drastically reduced by signal averaging, the PC's processor can be used to perform so-called super-averaging of the averaged waveforms. That can to extend the number of averages indefinitely.

As is the case with the FIR filtering, signal averaging is also compatible with CompuScope SDKs (software development kits) for C, C++, National Instruments LabVIEW, and The MathWorks MATLAB.

With all this discussion of signal processing and software, it's worthwhile mentioning that the CompuScope 12400 is also supported by quite a few of Gage's application packages.

A Windows scope

The press release briefly mentions Gage's GageScope oscilloscope software. For Windows 98, Windows ME, Windows NT, Windows 2000, and Windows XP platforms, it lets you capture and display up to 60 channels of signal on your PC, giving you features such as FFT (fast Fourier transform) analyses, waveform parameter analysis, extended math, and averaging.

The GageScope executables also let the CS12400 card AutoSave to disk. The software also supports transfer to PC-hosted downstream analysis packages such as the aforementioned MATLAB and LabVIEW, ass well as Mathsoft's Mathcad.

Lastly, it's worth noting that Gage Applied Technologies is a member of the Dynamic Signals group of companies. This consortium is known for its signal-capture and processing plug-ins.

KineticSystems, Preston Scientific, and Cyber Systems are all members of the Dynamic Signals family. This mix provides instruments and modules for PC-based test-and-measurement, as well as synthetic instrumentation built on PCI, PXI, VXI, CAMAC (computer automated measure and control), and proprietary platforms. You'll be in good company if you go with this card.

Unfortunately, at press time Gage hadn't supplied pricing info for this new product. I'll update this story when I get that specification.

- Alex Mendelsohn

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