USB-to-Synchronous Cable Enables IP Data Communications for Tactical Radios

Warfighters can benefit greatly from having radio IP-based data communications at the theater level. Unfortunately, the vast majority of the 750,000 tactical radio systems currently in use do not have the necessary built-in hardware and software to send IP-based data communications. The installed base of tactical radios is comprised of various makes and models that are not interoperable, further making it difficult to achieve theater-level data communications.

The ideal long-term solution is to replace all existing tactical radios with a new standard of Software Defined Radios (SDRs) that achieve both data-enablement and interoperability out of the box. However, technological delays and budget constraints continue to extend the timeline for SDR deployment.

Sealevel Systems has developed a high-throughput synchronous interface that works seamlessly with software developed by the Defense Information Systems Agency (DISA). The ACC-188 radio adapter and DISA Personal Digital Assistant (PDA)-184 software allow warfighters to quickly transmit and receive data such as GPS maps, images, coordinates, and IM-type communications using existing tactical radios.

USB Synchronous Interface Cable

The radio adapter connects to the standard USB port on any laptop or desktop computer. A six-foot cable is terminated with the appropriate connector to make the adapter compatible with the most prevalent brands and models of field radios including Harris PRC-117 and PRC-152, Raytheon PSC-5D and ARC-231, Thales PRC-148 and PRC-150, Motorola LST-5, and Rockwell Collins ARC-210. The ACC-188 can be adapted for most digital radio sets that have a synchronous serial data port by terminating the cable with the appropriate radio connector and pin out.

Converting the radio waveform to USB data is performed by circuitry and firmware contained in a waterproof “bump” in the cable. Many ruggedized military computers still do not have USB 2.0 ports, so the adapter is designed to work with a standard USB 1.1 (12 Mbit/s) connection to the computer. USB is an asynchronous interface that relies on the USB host controller to poll the USB I/O device for data. Since the radio transmits continuous high-speed synchronous data, often for extended time periods, the conversion to asynchronous USB required careful attention to a variety of critical timing elements.

The heart of the design is an 8-bit microcontroller with integrated USB port and a Field Programmable Gate Array (FPGA) device. Considering that the USB port on the host computer fully powers the adapter, the design is optimized to consume less than 3 watts to minimize battery drain when used with laptops. This feature is vitally important in battlefield situations where soldiers may not have the ability to recharge their laptop batteries for extended periods of time.