Microwave Journal
www.microwavejournal.com/articles/26746-high-speed-pxie-digitizers

High Speed PXIe Digitizers

July 14, 2016

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When it comes to modular instrumentation the PXI standard has become today’s most popular choice for the automated test industry. With its high quality mechanical and electrical design, and wide range of suppliers and modules, PXI has proven to be the ideal platform for many industrial and mobile applications. Constantly evolving, the latest PXI Express (PXIe) systems are now based on PCI Express (PCIe) technology that provides data throughputs some 10 to 20 times faster than the earlier generation of PXI products. Faster throughput means shorter testing times and improved system productivity.

To allow users to harness these capabilities, Spectrum GmbH has released its first high-speed digitizer product line based on the PXIe standard. The M4x.44xx series consists of six new digitizers (shown in Figure 1) each packaged in a dual width 3U PXIe module and incorporating a four lane PCI Express Generation 2 interface. With data transfer speeds in excess of 1.7 GB/s the high-performance interface allows the new modules to be used in today’s fastest PXIe mainframe systems (see Figure 2).

However, it’s not just data transfer speed that makes these new PXIe digitizers stand out. They also set new standards for sampling rate, resolution and channel density. Versions come with either two or four fully synchronous channels and resolutions of 14 bits, for sampling at rates up to 500 MS/s, or 16 bits for sampling at rates up to 130 or 250 MS/s.

With analog bandwidth up to 250 MHz the digitizers are ideally suited for use in ATE systems where electronic signals in the 1 to 200 MHz range need to be acquired and measured with the best possible speed and precision. Typical applications include semiconductor and component testing, radar, wireless communications, medical science, transportation, power, physics, surveillance, aerospace and military.

Designed to handle the widest range of input signals the modules incorporate an oscilloscope style front-end. Each channel has its own separate monolithic ADC and low noise signal conditioning circuitry. Fully programmable, the cards provide six gain input ranges (from ±200 mV up to ±10 V), selectable input impedance of 50 Ω or 1 MΩ and AC or DC coupling. A powerful trigger system and versatile clock adds to the overall flexibility. The trigger source can be any of the input channels, either of the two external trigger inputs, any of the eight PXI trigger lines or the PXI star trigger. Trigger modes include positive or negative edge, window (both edges), logical multi-source (pattern), software and rearm.

Figure 1

Figure 1 The M4x series includes six new PXIe modules featuring two or four channels, 14- and 16-bit resolution and sampling rates of 130, 250 and 500 MSPS.

The clocking system of the digitizers is cutting edge. The clock can be internally or externally generated (including using the 100 MHz PXIe differential clock and the 10 MHz PXI clock as a source). It has a built-in 10 MHz reference which, if required, can be synchronized with other reference sources. A fine-resolution mode is also available that allows clock rates to be selected with 1 Hz resolution. This useful feature makes it possible to program the sampling rate to match that of other devices or specific input signals.

Each module is equipped with a generous 4 GByte (2 Giga Samples) of on-board acquisition memory, making it simple to acquire long and complex signals. The capability is further enhanced by a variety of data acquisition and readout modes. These include single-shot capture (transient recording), streaming (FIFO), segmented (multiple recording), gated (gated sampling), or the combination of segmented acquisition of fast signals in parallel with slow continuous data recording (ABA mode). A trigger time stamp feature even identifies when events occurred and makes it easy to measure the time between them.

The high-resolution ADCs combine with the low noise front-end electronics and accurate clocks to ensure the digitizers deliver outstanding dynamic range and performance. For example, signal-to-noise ratios (SNR) are typically over 70 dB, spurious free dynamic range (SFDR) is better than 90 dB and total harmonic distortion (THD) is less than -70 dB. These specifications make it possible to detect small signal variations on larger ones and also allow better measurement repeatability, precision and accuracy.

The new PXIe modules are based on Spectrum’s proven M4i series of PCIe cards and deliver the same advanced features and signal quality. As the PXIe modules have a smaller footprint than their equivalent PCIe cards, a new base board was designed (see Figure 3). A modular concept was used so that different digitizer or generator front-ends can be shared by both PCIe and PXIe platforms. This modularity will also enable the release of several new PXIe products within a short time — all sharing a common software interface that’s similar to existing PCIe, PCI and PXIe products.

Figure 2

Figure 2 The M4x.44xx series fits into any PXIe system with two free slots.

Figure 3

Figure 3 The M4x.44xx series has a new base board (top) that accommodates the existing M4i series digitizer (bottom) and generator hardware, allowing rapid product development.

Those users wanting out-of-the-box operation of the digitizers can utilize the powerful SBench 6 program, which supports all the key functions of the digitizer as well as providing data display, storage, analysis and documentation. The program allows both oscilloscope and transient recording modes, including continuous data streaming. A base version of SBench 6 is provided free of charge.

Customers who need to develop their own programs can use the proven Spectrum drivers (available for Windows and Linux), which are included as standard. A set of programming examples is provided to illustrate the card’s main signal capture functions. Support covers programming in Visual C++, Borland C++, Gnu C++, LabVIEW, MATLAB, Visual Basic, VB.NET, C#, J# and Delphi code.

The new M4x series modules come complete with software drivers and a two year manufacturer’s warranty, together with free technical support, including software and firmware updates.

Spectrum Systementwicklung Microelectronic GmbH
Grosshansdorf, Germany
www.spectrum-instrumentation.com/en