Spectrum Instrumentation, a digitizer and generator specialist, announced on the 19th that it is implementing digital down conversion (DDC) functionality in its PCIe digitizer product line.

DDC is a technology frequently used in a wide range of communication systems such as digital radio, radar, mobile communications, and space/satellite communications. It converts PF or microwave signals into baseband signals containing important SOI (Signals of Interest) to reduce the measurement signal result value and improve signal quality and measurement accuracy.

Spectrum Instruments described the DDC function as being ratio-efficient for using external GPUs for continuous real-time processing. Spectrum Instruments currently has 48 PCIe digitizer families with sampling rates from 5MS/s to 10GS/s.

■ Built-in FPGA-based DDC vs. external GPU-based DDC

Most digitizer DDCs use a fast and efficient onboard FPGA (Field Programmable Gate Array) approach to convert the incoming analog signal into digital data and pass it on to the FPGA for down conversion. However, implementing an FPGA-based DDC has limitations in that it requires not only large and expensive FPGA technology, but also specialized firmware, firmware development knowledge, and expensive software tools.

Spectrum Instruments, on the other hand, has overcome these limitations by streaming data collected with its own SCAPP (Spectrum’s CUDA Access for Parallel Processing) software development kit directly to the CUDA GPU via the digitizer PCIe bus. Since GPUs have thousands of cores operating in parallel, it is possible to implement processing software using the C/C++ language, which can be customized with common programming techniques, making it easy to implement DDC.

Additionally, SCAPP provided DDC example code and a platform for software optimization.

■ Operational example running at 12.8GB/s streaming speed

The Spectrum Digitizer family consists of three different platforms: M2p, M4i, and M5i. They feature ultra-high sampling rates from 5 MS/s to 10 GS/s, resolutions from 8 to 16 bits, and bandwidths from 2.5 MHz to over 3 GHz. The M5i series, for example, supports the highest sampling rates and bandwidths, 12-bit resolution, and ultra-high-speed data streaming (12.8 GB/s) over the PCIe bus.

As an example of a spectral digitizer DDC, the M5i.3337-x16 acquires a 702 MHz input signal at 6.4 GS/s and streams it to an Nvidia RTX A4000 GPU (6144 cores) at 12.8 GB/s, where it passes through a digital synthesizer (DDS) to mix sine and data and apply a moving average to reduce the output. Afterwards, it is transferred to PC memory through a Finite Impulse Response (FIR) filter for storage or further processing.

The signal-to-noise ratio (SNR) of the converted signal is improved by about 10 dB compared to the original, and the data file is reduced by about 512 times. Since the important information of the signal is still maintained, it is easy to store, analyze, and display on a PC.

Spectrum Instruments explains that the new DDC capability is available as part of the SCAPP package, a software package that can be used to combine new or existing Spectrum digitizers with GPUs.