Radar technology is undergoing major changes as the high volumes of automotive applications drive more innovation. This is changing the mix between short- and long-range technologies, driven partially by government regulations aimed at reducing interference.
Long-range radars have conventionally used 77-79 GHz frequencies, while 24-26 GHz radars provided short-range monitoring. The latter usually has lower cost, making it attractive.
However, the drive to focus on one technology has prompted developments that let systems extend their capabilities. These efforts come amidst uncertainty surrounding 24 GHz, which is limited by European regulators. Some feel these rules spell long-term doom for 24-GHz systems.
“We have migrated to 77 GHz because it can be used in any region,” said Kay Stepper, Director of Marketing, Product Planning and Innovation Management at Bosch Chassis Systems Control, North America. “There’s also an advantage in focusing; the lens in front of the radar can be focused for either short or long range.”
However, the pathway for dominance is not without roadblocks. Many observers feel that 24-26 GHz systems may be able to carve out some niches. Costs are currently below those of high-frequency radars, forcing engineers to consider low-frequency systems in regions that do not have regulations that limit usage.
“Things have changed from a couple years ago when the long-term bet was on 77-79 GHz radar,” said Martin Duncan, Innovative Systems Manager at STMicroelectronics. “There’s more production going on in 24-26 GHz space due to its low cost.”
Another selling point for the low frequency is its ability to transmit through plastics. That makes it easy to hide, which is a big benefit in applications where it is difficult to put windows that let 77-GHz signals pass through.
“We’re not sure about the future of 24 GHz, but we’re currently using it for side-looking blind-zone sensing,” said John Capp, General Motors’ Director of Global Safety Technology Strategies. “The 24-GHz radar can see through the fascia material that covers it.”
Though this ability to go through materials is a major benefit, observers note that things often are not as simple as they seem. Certain materials will block 24-GHz signals. If purchasing agents acquire different paints during a production run, the radar may not work as well.
“With 24 GHz, it can be a huge headache if paint is changed,” Duncan said.
Though 24-GHz systems have their place today, some companies predict that it is only a short-term role. As the trends to smaller cars and lighter weight evolve, the benefits of 24-GHz modules may be negated by pressure from stylists and others who want valuable real estate in front ends and elsewhere.
The high-frequency challenger has a smaller antenna, which is a major contributor to a radar module’s size. “With 77 GHz, the antenna is around three times smaller than a comparable 24-GHz antenna,” said Dieter Hoetzer, Manager of Engineering for Driver Assistance at Bosch Chassis Systems Control.