The frequency range for aircraft has expanded dramatically since the 1980s, when it was expanded from military UHF to include military VHF and UHF (30-400 MHz). Radio suppliers are using a range of techniques to handle this growth.
The proliferation of frequencies has driven a lot of interest in software defined radio (SDR), but the idea of using many programs on a single digital platform has not seen the success once envisioned. Most aircraft still carry multiple radios even though many suppliers tout the benefits of SDR.
“Combining functionality into a single radio case is the ultimate goal,” said a Raytheon spokesman. “Ultimately this reduces weight on the aircraft, while at the same time increasing the number of communications/data channels in equal or lesser size weight and power package.”
Some vendors have been using the concept for quite a while. That’s helping reduce the size of core radios.
“Every new radio that we have designed in the last 10+ years has been some sort of SDR. That includes all of NAV Radios, COM Radios, and our tactical FlexComm II systems,” said John Markham, Senior Program Manager at Cobham Avionics. “For end users, it means quicker adoption of new standards and ability to selectively match features to the mission.”
But some aircraft makers note that while SDR concepts are moving forward, most aircraft still have multiple radios.
“The reality of true SDR has been much slower in materializing than originally anticipated,” said a Boeing engineering spokesman. “It should provide platforms with a faster/lower cost capability upgrade, via updating radio software for a new waveform, than in times past when new radio hardware was required.”
The support technologies used to add a new frequency are a big factor in the slow uptake. Whenever new frequencies emerge, ancillary components can drive costs upward quickly.
“One challenge for SDR is if the new waveform requires any change in the supporting RF infrastructure in the airplane, such as antennas, power amps, RF cable, and other components,” the Boeing spokesman said. “If so, the costs associated with the retrofit may still represent the majority of the retrofit costs, even if you don't buy a new radio. Another challenge is if the aircraft infrastructure also requires an update to include new data interfaces with the radio.”