Recent advances in vehicle radar technology are about to create a step change in capabilities that will provide the broadest possible operating performance for advanced driver-assistance systems (ADAS).
There are two primary ways to improve ADAS perception. We can either improve the way the system interprets data coming from the sensors by using machine learning, or we can improve the quality and accuracy of the actual data coming from the sensors. Combining these approaches has a multiplier effect, creating a robust environmental model that vehicles can use to make intelligent driving decisions.
While machine learning continues to evolve, so does radar sensor technology. One particular approach engineers have recently had success with is to use 3D air-waveguide technology in radar antennas to capture more precise signals and extend range.
Wave of the past
A waveguide is essentially a miniaturized rectangular tunnel or pipe that can carry high-frequency radio waves. Its inner surfaces are made of metal or coated with a metallic substance so that any radio waves that enter the tunnel will reflect off the inner walls and propagate further into it.
Historically, automotive radar has ingeniously used the structure of a printed circuit board to create these miniature waveguides. Printed circuit boards are composed of layers of laminate sandwiched between layers of copper. The copper layers become the top and the bottom of the waveguide. To create the sides of the waveguide, engineers use two rows of small, drilled holes, called vias, that are coated with metal.
Radio waves enter the waveguide through the laminate and travel the length of the waveguide in that same substrate. While this approach works well for many applications, all resins and plastics — even expensive laminates designed for this application — dampen the strength of a signal more than air does.
Wave of the future
As one might imagine, manufacturing miniaturized and reproducible tunnels filled with air is not easy, and doing so in a cost-efficient manner is even more difficult. Manufacturers have tried using molded plastics and then coating them with metal, which allows them to shape the 3D structure of the waveguide.
To make Aptiv’s latest radars, we create molded 3D air waveguides using a special technique that allows for even more degrees of freedom in the design, enabling us to employ unique shapes and beamforming techniques to create special radar beams. We can tailor the shapes to achieve the goals of specific applications.
Immediate results
In a vehicle radar system, 3D air-waveguide antennas help to efficiently illuminate the environment with radar signals and receive the faint echoes coming back from the environment with low loss. By reducing the transmitted and received signal losses, air-waveguide antennas enable a more sensitive sensor — while maintaining the radar’s same small physical footprint. What is more, air-waveguide technology enables these improvements while keeping costs down.
Aptiv has been using slotted waveguide antennas based on high-frequency plastic laminates for more than a decade and is bringing this experience to 3D air-filled waveguides. For example, with larger apertures and intelligent beamforming, we can achieve higher angular resolution for more precise perception.
The result is that the perception system receives more of the data it needs to pinpoint the position of objects around the vehicle, how fast they are moving and even what those objects are.
This approach is also compute-efficient, because – in contrast with camera-centric systems – these improvements do not pass along extraneous data that must be discarded. For example, a camera picks up the color of a vehicle blocking the lane ahead, but that data does not help the ADAS system decide how to move to avoid it. Rather, a sharper radar image only helps the perception tracker software’s accuracy.
A self-parking alternative
Radars with advanced 3D air-waveguide antenna technology could support a high-definition perception mode to enable self-parking. Early implementations of self-parking capabilities rely on ultrasonic sensors to measure the width of parking spaces, which often means the vehicle has to drive past a parking space to determine whether it is the right size, and then back up into it.
Using tracker software that leverages enhanced radars, the vehicle would be able to determine the size of the space before driving past it, allowing the vehicle to pull directly into it.
An OEM could choose to activate this particular feature via software only for customers who request it through an over-the-air software update, without increasing the complexity and cost of the device.
The next generation arrives
At Aptiv, our seventh-generation corner radars and forward-facing radars incorporate air-waveguide antenna technology based on proprietary intellectual property and a unique design.
In the forward-facing Aptiv FLR7, we have created the industry’s first base-level radar with 4D capabilities, with an industry-leading range of 300 meters and excellent angular resolution. The fourth dimension in 4D radar is elevation, which allows the radar to significantly reduce false positives in automatic emergency braking situations as well as in cruise-control applications. For example, even though manhole covers could reflect signals strongly, the system could detect that they have very little height and would avoid engaging the automatic emergency braking system.
With the enhanced technology, some OEMs could opt to remove the forward-facing radar altogether, using the extended range and wide field of view of the Aptiv SRR7+ corner radars to cover both front corners and the area directly in front of the vehicle. This configuration can support standard adaptive cruise control and automatic emergency braking.
Aptiv’s next-generation radars anticipate the increased bandwidth needed to accommodate the data such systems will require, so all of them support Automotive Ethernet with raw data streams up to 1G bit/sec.
By leveraging advanced antenna technology, high-speed data support and software enhancements — all in a compact package — the seventh-generation radar family from Aptiv provides an excellent sensing foundation to build the next generation of automated driving.
