Automatic signal analysis speeds up development

July 20, 2014 //By Christoph Wagner, Rohde & Schwarz
Automatic signal analysis speeds up development
<p>In the aim of reducing accidents, today's vehicles are increasingly equipped with technologies that provide support to the driver in critical situations. Besides cameras and ultrasonic sensors, the automotive industry is turning more and more to radar as the cost of the associated technology decreases. Radar allows very fast and clear-cut measurement of the velocity and distance of multiple objects under any weather conditions. This is enabling solutions for automated driving. The relevant radar signals are frequency-modulated and can be analyzed with spectrum analyzers. In this manner, developers of radar components can automatically detect, measure and display the signals in the time and frequency domains – even up to frequencies of 500 GHz. </p>

According to a study by the Audi Accident Research Unit, more than 90 % of all accidents on the road can be attributed to human error. Furthermore, the accident rate could be drastically reduced by implementing automated driving (similar to the autopilot systems used in aircraft). Although it might sound like something from a science-fiction novel, automated driving has already become reality in many cars in the luxury class and now increasingly in the medium-price class too. Besides the now classic parking-assistance system, there are other functions to help with everyday driving such as a lane-change assistant, blind-spot detection and adaptive cruise control. While a parking-assistance system is based on a clear yes/no procedure where information is paramount, adaptive cruise control can involve modifying the driving speed in response to the vehicle in front, for example.

Maintaining the flow of traffic

Another reason why automated driving has become such an important topic is related to the rapid development of megacities. The International Energy Agency has noted that as cities like Moscow, Shanghai, Tokyo and Mexico City attain populations of 20 or even 30 million, they are experiencing a dramatic increase in vehicle usage. Today, there are already more than one billion vehicles in the world. In 2025, there will be 1.5 billion vehicles, including 400 million in China alone, where they will be concentrated in metropolitan areas. In such a context, automated driving will no longer be merely a question of road safety and convenience. Instead, it will offer the only way to keep traffic flowing in cities, where the average speed is already less than 20 km/h due to extreme road usage.

Radar technology for automotive applications

Radar technology for use in cars differs in several ways from the military applications for which radar was originally developed. Firstly, the automotive industry is subject to enormous cost pressures, so components must be much more economical. In addition, due to the very limited space for radar sensors behind plastic bumpers, the sensors must be extremely compact.

Compared with camera and ultrasonic applications, radar has a major advantage in that no visual contact is required between the radar sensor and the object to be detected. This saves costs in the production of bumpers and can also be exploited in the vehicle design. However, it is still a challenge to compensate for the attenuation of the transmit and receive signals as they pass through the different layers of material in the bumper as well as the (metallic) paint. Such compensation is implemented with postprocessing in the radar sensor.

For automotive applications, vehicle manufacturers can currently make use of four frequency bands at 24 GHz and 77 GHz with different bandwidths. While the 24 GHz ISM band has a maximum bandwidth of 250 MHz, the 24 GHz ultrawideband (UWB) already offers up to 5 GHz; however, this is allowed only until the end of 2022 due to international regulations. The band that will be available past this date with up to 4 GHz bandwidth lies between the frequencies of 77 GHz and 81 GHz. It is already used for forward-looking applications. Since the signal bandwidth determines the range resolution, it is very important in radar applications. Accordingly, the other allocated frequencies of 122 GHz and 244 GHz for this application with a bandwidth of only 1 GHz will see little use in the automotive industry and are restricted to research projects until further notice.

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