Modular PXIe digitizers target wideband applications

Modular PXIe digitizers target wideband applications

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By Nick Flaherty

The new M4x.22xx series includes modules that offer one, two or four fully synchronous channels, each with its own 8bit analogue-to-digital converter (ADC) with real-time signal sampling at rates from 1.25 GS/s to 5 GS/s and scope-like signal conditioning circuitry that allows programming of parameters such as input gain, signal offset and coupling.

The digitizers also offer bandwidth up to 1.5 GHz making them ideal for automated testing applications where wideband electronic signals from DC to the GHz range need to be acquired and analyzed. Typical applications include semiconductor and component testing, radar, wireless and digital communications, laser and optical systems, automotive, power, physics, surveillance, medical science, aerospace and defense.

The flexible front-end circuitry of the digitizers is complemented by a powerful trigger system, an on-board acquisition memory of 4 GSamples and a range of data acquisition and readout modes. This combination makes it simple for the cards to capture complex signals as well work effortlessly with other modules in a test system. For example, the trigger source can be any of the digitizers 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, both edges (window) and software. In addition, logic triggering can be implemented based on the state of the channel and the external trigger inputs.

Acquisition and readout modes include single-shot capture (for transient recording), FIFO (for streaming data directly over the bus), segmented memory (Multiple Recording), gated acquisition (Gated Sampling) or the combination of segmented acquisition of fast signals in parallel with slow continuous data recording (ABA mode). Trigger events can also be time stamped to know exactly when they occurred.

All the M4x.22xx series digitizers are packaged in a dual width 3U module, which incorporates a four lane PCI-Express Generation 2 interface. The interface allows data transfer speeds in excess of 1.7 GB/s for today’s high-performance PXIe mainframe systems.

For rapid waveform display and analysis, acquired data can be transferred to an embedded or external processor. In addition, data can be shared with other modules like arbitrary waveform generators (AWGs) to create more sophisticated capture-replay or stimulus-response, testing scenarios. The digitizers are all optimised for dynamic performance. On-board calibration is standard and a high quality clocking system drives the 8-bit ADCs on each channel synchronously so that timing measurements are precise and inter-channel phase errors are minimized. The dynamic parameters provide effective bit measurement (ENOB) up to 7.5 bits, signal-to-noise ratio (SNR) up to 46.9 dB and spurious free dynamic range (SFDR) of over 62 dB.

The modules also incorporate the latest in FPGA-based firmware so that acquired data can be processed on-board prior to being transferred over the bus. Block averaging and block statistics packages are available for high trigger rate applications that require hardware-based processing functions. Block averaging can be used to reduce signal noise and improve measurement resolution, while block statistics perform a peak detection process that yields a waveform’s maximum, minimum and average values.

To allow easy integration into any test system, the units are shipped with a host of software tools so that users can create their own control programs with almost any popular programming language. This includes C++, Visual Basic, VB.NET, C#, J#, Delphi, Java and Python code. Third party software support is also provided for LabVIEW, LabWindows and MATLAB. For users not wanting to write software, Spectrum also offers its powerful SBench6 Pro software. This enables users to control all of the digitizer’s operating modes and hardware settings from one simple, easy-to- use, graphical user interface. The software has a host of built-in features for waveform display, data analysis (such as FFT, parameters and mathematics) and documentation. Waveforms can also be stored and exported to other devices and software programs using the most popular formats such as ASCII, binary and Wave.

The M4x.22xx digitizers are available with immediate delivery. All units are shipped factory-tested and include a base version of Spectrum’s SBench 6 software, support drivers for most popular programming languages and a two year anufacturer’s warranty. Technical support, including software and firmware updates, is available free of charge.

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