86 The past few years have seen a marked rise in demand for transponders, transceivers, and related solutions for the identification and air traffic management (ATM) of UAVs. Accompanying this is a general consensus across crewed and uncrewed aviation spaces that Automatic Dependent Surveillance-Broadcast (ADS-B) will surpass secondary surveillance radar (SSR) as the common standard by which all next-generation aircraft can be tracked, and collisions or excess traffic in the air can be safely avoided. As a reminder, an ADS-B transponder works by periodically broadcasting its host aircraft’s GNSS position, altitude, velocity and identification codes; sometimes (but not necessarily) as a response to receiving an interrogation signal from ground- or air-based devices – a function typically referred to as ‘ADS-B Out’. Through such information, which is often more accurate and useful than SSR data, ATM authorities can securely separate aircraft over radio instructions, and general or uncrewed aviation pilots can take safety-critical evasive action. Receiving such data is a functional capability termed ‘ADS-B In’. Around 80% of crewed aviation already uses ADS-B, often through the use of a Mode 5, Mode S or Mode S Extended Squitter (S-ES) transponder (which integrate ADS-B Out functionality as standard). Arguably, the only problem with ADS-B Out is its frequency bands: it must be broadcast at either 978 MHz or 1090 MHz. These frequencies are also used by Mode A and C transponders, as well as radar and other systems, making for painfully crowded bands. Hence, many anticipate that the older, less detail-heavy transponder modes will be disabled in time to free up their transmission frequency bands for ADS-B (such as military Modes 1, 2, 3 and 4, and civilian Modes A and C, with Mode S possibly included too). For all these reasons, manufacturers seeking to build certifiable UAVs are Rory Jackson finds out the latest in innovation, regulation and production of transponders for keeping UAVs flying safely in the skies Now you see me August/September 2024 | Uncrewed Systems Technology A new generation of ADS-B transponders compliant with the latest and highest Technical Standard Orders on certifiable performance is entering production (Image courtesy of uAvionix)
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