Austin, TX. The modern RF battlefield presents a variety of threats, according to Wan Liu, a product manager at NI’s Ettus Research brand. Speaking at NIWeek’s Aerospace and Defense Summit, he cited several trends: use of COTS components, the increasing quality of assets, the increasing variety of threats, and the rapid evolution of waveforms, protocols, and devices. The threats affect not just military organizations but law-enforcement agencies, regulatory bodies, security firms, and first responders. The prevalence of drones exacerbates the threat, he said, disrupting investments in ground-based security systems.
Responding to threats, Liu said, involves spectrum monitoring to scan, detect, analyze, classify, decode, and record signals. Spectrum monitoring requires frequency-agile wide-bandwidth instruments able to capture short-duration signals in real time. Threat identification also requires direction-finding/geolocation using angle-of-arrival (AOA) and time-difference of arrival (TDOA) techniques, which require high-channel-count systems featuring phase coherency and able to evaluate compute-intensive DSP algorithms for channelization, correlation, and beamforming.
To address the threats, Ettus Research offers software-defined radios, including USRP X310 motherboards, which include 14-bit 200-MS/s ADCs and 16-bit 800-MS/s DACs plus a Kintex-7 FPGA. Each board supports 10 GbE and PCIe x4 streaming and fin it a half-wide 1U form factor; a board-only option allows for OEM integration.
The motherboards work with a variety of daughterboards, including the TwinRX, which features a dual-channel superheterodyne receiver offering up to an 80-MHz bandwidth from 10 MHz to 6 GHz.
Software suitable for SDR applications includes LabVIEW, GNU Radio, and MATLAB. Engineers might use LabVIEW for system modeling and design and then use LabVIEW FPGA to program the SDR hardware, Liu said. Or they might use GNU Radio for system modeling, C++ or Python for design, and Ettus Research’s RFNoC (RF network on chip) for the FPGA. He described GNU Radio as a free and open-source tool widely used in government, commercial, and academic environments supported by a large ecosystem of SDR vendors.
He concluded by presenting a direction-finding example using the MUSIC algorithm, an open-source reference application developed in GNU Radio. The example employed the USRP X310 and TwinRX to implement the MUSIC algorithm using a 4-element sensor array and LO sharing for phase-coherency. For details visit https://github.com/ettusresearch/gr-doa.
