PCIe digitizer cards add digital down conversion
Spectrum Instrumentation in Germany has added digital down conversion to its line of PCIe digitizer cards by using an external GPU-card for continuous “on-the-fly” processing.
DDC is widely used in communication systems such as digital radio, radar, mobile telephony, space or satellite communications to convert RF or Microwave signals to baseband frequencies.
The conversion dramatically reduces the resultant data set while also improving signal quality and measurement accuracy. The approach of using an external GPU card rather than on onboard FPGA means the 48 different PCIe cards can use the DDC function with sampling speeds from 5 MS/s to 10 GS/s.
By using the 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 C or C++. 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. This includes a Direct Digital Synthesizer (DDS), lowpass filtering and down sampling. The GPU performs all the necessary DDC tasks, mixing the data with a complex sinusoid generated by the DDS, applying a moving average, decimating the result and passing the decimated data through a Finite Impulse Response (FIR) filter. The GPU also rescales it and then transfers the processed data to the PC memory for storage or further processing. This can Reduce the data file by a factor of 512, but still retains all the important information in the signal frequency range of interest. The smaller data file is now much easier for a conventional PC to store, analyse and display.
From now on, the new DDC feature is part of the low-cost SCAPP package. This software package is needed to combine new or existing Spectrum digitizers with a GPU-card.
www.spectrum-instrumentation.com
If you enjoyed this article, you will like the following ones: don't miss them by subscribing to :
