Keysight PXI intro: FPGAs and fast displays

-March 31, 2017

Keysight Technologies recently introduced 10 new PXIe (PXI Express) instruments. The instruments included three arbitrary waveform generators (AWGs) up to 1 GHz of bandwidth, two digitizers up to 500 Msamples/s sampling rate, two combination AWGs/digitizers, and three “fully featured” oscilloscopes up to 1 GHz of bandwidth.  The sheer number of products signals Keysight’s continued commitment to exploit the advantages of PXI to address solutions in their target markets.

And what would those advantages be?  I had the fortune to discuss the introduction with Sheri DeTomasi, Keysight’s Modular Program Lead.  She showed a diagram that represented Keysight’s summary of the benefits of modular, specifically PXI and AXIe.

Figure 1 The many advantages of PXI and AXIe modular instruments. Image courtesy of Keysight Technologies.

Frequent readers of the Test Cafe blog recognize many of these same elements called out regularly in my columns. Keysight has shown this chart before, but this time there is something new- an additional advantage “Easier to customize,” with specific mention of FPGA customization. Indeed, six of the ten modules introduced included the ability for the user to customize the embedded FPGA to enable tight time synchronization and custom signal processing algorithms.

Astute industry watchers will recognize those six FPGA-enabled modules as being from Signadyne, a Spanish company acquired by Keysight last summer. It would be a mistake, however, to diminish the importance of this introduction as a mere rebranding. Keysight’s apparent decision to embrace FPGA customization inside of instruments ups the ante of what will be expected of instruments in the future.

I’ve written about FPGA customization before, most notably by National Instruments using their product LabView FPGA. NI is not alone, as several vendors have offered their embedded FPGAs as user customizable to some degree. NI was unique, as they had a standard method across their product line for the customization. Now, with six products customized by standard products and methods, it appears Keysight is doing so too. Let’s take a look under the hood.

Figure 2 In this diagram of the programming options for the M3xxxA series of PXI instruments, the block arrow titled “SW Programming” is the standard method for automating instruments, through the test system controller.  The block arrow titled “HW Programming” shows two methods of modifying the embedded FPGA. Image courtesy of Keysight Technologies.

Figure 2 shows the programming options available to the M3xxxA series of PXI instruments, essentially those that have user accessible FPGAs. These instruments may be automated using traditional methods indicated by the block arrow titled “SW Programming.” Here, common programming languages and automation environments are deployed on a test system controller to send commands to the instrument and receive data back.

The block arrow titled “HW Programming” leads to the FPGA customization. The customization is done outside of run time. Once customized, the user then uses the traditional method of software control during run time, but the module is now a customized instrument. There are two software products for customizing the FPGA. The M3601A Hardware Virtual Instrument design environment is dedicated to achieving customized tight time synchronization on or between modules. The M3602A Graphical FPGA design environment programs the actual operation of the FPGA, and therefore the instrument.

The user uses the Graphical FPGA environment to link together routines generated by a variety of methods. There is a ready-to-use standard block library. Alternatively, the user can include existing IP generated in MATLAB/Simulink, VHDL, or VIVADO/ISE.  Keysight claims that they’ve implemented a technique that suffers no speed penalty versus hand written HDL code. Once the code is compiled, the instrument may be “hot programmed.” That is, FPGA images may be downloaded over the PXI backplane without rebooting the instrument. The Soft Front Panel (SFP) available for all Keysight modular instruments includes the ability to download the embedded FPGA code to the instrument.

Keysight showed two applications using custom generated code. One involved a Digital Pre-Distortion (DPD) algorithm downloaded to an AWG. DPD techniques are used in RF systems to deploy lower cost components that inherently have higher distortion. By pre-distorting the signal in a unique way, a clean signal may be generated by these non-ideal components. In testing scenarios, the DPD algorithm is desired to be embedded within the test equipment. A second application was shown involving the tight time synchronization required in quantum computing. In this case, a PXI digitizer and AWG were coordinated using the HVI design environment. A decision made by the FPGA on the digitizer was immediately transferred to the AWG over the PXI trigger lines, causing a change in the AWG sequence engine.

There was one more architectural surprise from Keysight. To read about it, you will need to click ahead ...

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