Improving safety with integrated solutions for automotive radar
Safety is one of the most important issues in the automotive market today. More vehicles on the road and higher speeds increase the potential for accidents, while more comfortable cars mean that drivers can lose their sense of risk. An ageing population can also contribute to a higher rate of accidents.
Semiconductors are stepping up to meet these challenges and make cars safer. As crash detection begins to merge with other electronics in the vehicle, such as active safety systems, communications, and advanced driver assistance, the automobile is becoming more autonomous and more intelligent. Electronic systems that can act faster than the driver will be able to take control to reduce the severity and frequency of accidents, saving lives on the roads.
In the area of active safety, systems enabled by radar technology are becoming more prevalent. Adaptive Cruise Control (ACC) allows the driver to set a safe ‘follow distance’ to the car in front of them, and automatically accelerates and decelerates the car to keep that follow distance constant. Some systems also include automatic braking features that will apply the brakes if the car in front stops quickly or if an object blocks the road.
Similarly, Blind Spot Detection (BSD) in its simplest form informs the driver via a visual or audible signal when there is an object in the rear blind spot. There are also systems with autonomous features, such as prevention of lane change when an object is detected in the blind spot.
As in-car radar moves from being a luxury option to a standard safety feature, and from high-end to mid-range cars, the adoption and growth rates depend on the system cost. As radar becomes more affordable, and offers better performance in terms of target classification and range resolution, it will become a more popular option.
For system designers, there is a need to add these safety features without incurring substantial cost while still meeting the automotive industry’s stringent quality requirements. Additionally, the radar sensor module must be kept small enough to fit into areas of the car, like behind the bumper, which were not originally designed to house such electronics.
Integrated solutions
How can radar system designers meet these challenges? If we look specifically at the analogue front end (AFE) – which is a key part of the overall system – there is a choice of two approaches, both with trade offs: discrete components or an integrated solution.
Discrete parts can be used to build a top-of-the-line custom solution, with every parameter optimised. But it will take more time, occupy more space and cost more to build a radar system of discrete parts than it is to use an integrated solution.
The alternative is to use an integrated chip which can enable the system designer to provide most of the features a car manufacturer is likely to want, even for multiple applications like ACC and BSD, at a fraction of the size and cost. Advances in on-chip signal conditioning let designers program the settings needed for different driving conditions, whether it’s city traffic or motorway cruising, all in one economical package.
Fig. 2: Analog Device’s radar front end contains all the electronic circuitry necessary to design multiple driver assist systems.
Recently available products provide the required signal conditioning and data capture circuitry on one IC. ADI’s AD8283 automotive radar analogue front end, for example, encapsulates the circuitry that enables a baseband platform for ACC, BSD, and lane change assistance (LCA) in a single 10mm x 10mm package.
With an integrated solution, you can expect to reduce the footprint by at least half. For example, the AD8283 takes up 50% to 80% less space than equivalent discrete parts.
The designer’s life is also made easier by having multiple channels on one chip, because the channels are well matched, and for the driver because the sensor has a wider range of detection. The ideal radar system would sense objects around the car in a 180-degree field of view, much like human peripheral vision. A receiver system equipped with as many as six channels can do this with better angular resolution since it receives a higher number of reflected signals.
Another benefit of the integrated approach is flexibility, particularly given the variability in requirements for radar systems. Integrated solutions can include built-in programmable features such as variable gain and adjustable filters. These reduce the time to market not only for the first system designed, but for all subsequent systems by enabling a platform design approach. For example, highway ACC requires a wide dynamic range, while ACC Stop&Go requires less range but greater field of view and faster response time to adjust to traffic immediately ahead. The user-programmable settings with integrated solutions like the AD8283 can accommodate both highway and congested driving, enabling system designers to address many customer requirements with a single platform.
About the authors: Jeff Postupack is marketing manager for the Automotive RADAR Market Segment at ADI. Sam Weinstein is product manager for the AD8283.
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