Spectrum Instrumentation’s complete line of PCIe digitizer cards can now perform Digital Down Conversion (DDC) thanks to a low-cost option that uses an external GPU-card for continuous “on-the-fly” processing. DDC is a powerful technique that is commonly used in a wide range of communication systems, like digital radio, radar, mobile telephony, space or satellite communications. In the DDC process, RF or Microwave signals are converted to baseband, which contains the signal of interest. The conversion dramatically reduces the resultant data set while also improving signal quality and measurement accuracy. Spectrum Instrumentation has 48 different PCIe-based digitizers (with sampling speeds from 5 MS/s to 10 GS/s) that can run the new DDC function, so customers can select the “Perfect-Fit” model for their application.
DDC with on-board FPGA or external GPU card?
Most digitizer DDC implementations use on-board FPGA (Field Programmable Gate Array) technology. The incoming analog signals are converted to digital data before being passed to the FPGA for down conversion. The approach is fast and efficient but comes with limitations. It needs large and expensive FPGA technology as well as purposely created firmware. Customizing the firmware is also a challenge, requiring specialist firmware development knowledge and costly software tools.
The approach from Spectrum Instrumentation removes these hurdles. By using the company’s SCAPP (Spectrum’s CUDA Access for Parallel Processing) software development kit, the data acquired by the digitizer can be streamed over the digitizer’s PCIe bus directly to a CUDA-based GPU. The GPU, which can have thousands of cores working in parallel, then allows the processing software to be created using the C/C++ language. This makes for a much easier DDC implementation as customization can be made with normal programming skills. Starting with a tested DDC example delivers immediate results and provides a platform from which further software optimization is possible.
The Spectrum Instrumentation digitizer line-up includes PCIe cards in three different platforms (M2p, M4i and M5i). These offer sampling rates from as low as 5 MS/s up to an ultrafast 10 GS/s, with resolutions from 8 to 16 bit, and bandwidths from 2.5 MHz to over 3 GHz. The M5i series, shown in figure 1, represents the top-of-the-range, delivering the fastest sampling rates and highest bandwidths, all with 12-bit resolution. Another key feature of the M5i series is their ability to stream data over the PCIe bus at a market-leading rate of 12.8 GB/s!
