Unmanned Systems Technology 003 | UAV Solutions Talon 120 | Cable harnesses | Austro Engine AE50R and AE300 | Autonomous mining | AUVSI 2015 show report | Transponders | Space systems

72 also protect against potential damage caused by high ambient temperatures, and sand and dust particles. For sea-going vehicles, environmental protection is a major consideration in transponder design. Not surprisingly, protection from salt water is key, yet COTS solutions can often be adopted in a similar fashion to the ground domain, with the possibility of using a COTS radio as a transponder in a waterproof chassis. COTS In the air domain, UAVs are increasingly adopting COTS transponder technology already designed for manned craft, rather than using bespoke designs manufactured for a specific airframe. This has important advantages for the operator, as it reduces the procurement cost of a UAV by saving on the expense of having to develop a specific transponder. The operator also benefits from reliability, particularly if the transponder already has several years of proven service behind it. Another asset of COTS transponders is that they do not need new frequency bands in which to operate, and although their effective range may be limited, they are immediately available for use. However, the knock-on effect of COTS adoption is that new UAV transponder designs are becoming increasingly rare – with proven solutions already on the market, why develop new technology? Companies may therefore no longer retain dedicated radio engineers to design transponders if they know that COTS solutions can be used. One potential consequence of this is that when existing COTS technology cannot perform a particular task – or set of tasks – required by a UAV transponder, a company may not have the in-house expertise to design a new one. Technologies such as field- programmable gate arrays (FPGAs) are greatly aiding transponder design though, as they allow transponder circuits to be configured on a chip to perform a specific task. They also allow digital techniques to be used in the transmission and reception of transponder traffic, which means the transponders can be programmed to configure the waveforms (the pattern of a radio communication and its propagation to ensure it performs a particular task) they use, the format of messages they send and receive, and their levels of cryptography to ensure that transponder traffic is robust against EW. This programming is achieved using software-defined radio (SDR) techniques, which allow a radio to change its frequencies and transmission pattern using software rather than having to retune the radio manually, and offers important benefits for transponder design. For example, whereas some Summer 2015 | Unmanned Systems Technology An Automatic Dependent Surveillance- Broadcast (ADS-B) protocol tracking kit (Courtesy of Sagetech) Technologies such as FPGAs are helping with transponder design, allowing circuits to be configured on a chip to perform a specific task