Nº 4 2013 > Road safety
Future trends for automotive radars: Towards the 79 GHz band
By Davide Brizzolara, Project Support Manager, ERTICO – ITS Europe
Road traffic crashes have become a major global challenge — so the search is on for ways of improving road safety.
Radar-based driver assistance systems are already in use. Up to now, these have largely been comfort functions, such as adaptive cruise control, collision warning systems, blind-spot monitoring, lane-change assistance, rear cross-traffic alerts and back-up parking assistance. These systems obviously also enhance safety to some extent, but technological advances now permit proactive safety features such as collision mitigation systems and vulnerable road user detection.
In order to provide these essential functions for car safety, systems must be able to distinguish more clearly between objects on the road. This requires more bandwidth than the narrowband frequency ranges in the 24 GHz and 76 GHz bands that are used at present.
Wide bandwidth and high power limitation will enable better resolution and better object distinction. These are essential for new functions such as pedestrian detection or autonomous emergency braking in urban areas.
Benefits of the 79 GHz band
Higher frequency radar systems tend to perform better because they are more reliable and more accurate. This has been shown by several studies, including the European Union’s More Safety for All by Radar Interference Mitigation (MOSARIM) project (www.mosarim.eu).
Along with a greater capability for distinguishing between objects, the main advantages of the 77 GHz to 81 GHz frequency range (79 GHz band) are that radar devices can be much smaller, a single technology can be used for all applications, and the risk of mutual interference is low because of the smaller emission power required.
Clearer and more accurate pictures
Multiple objects cannot be distinguished if they appear in the same range gate. In such a case, spatial resolution is low, and several objects are fused into one virtual object (see Figure 1). This is what happens currently with the use of narrow bandwidth. The possibility of using a large bandwidth of 4 GHz, available around 79 GHz, allows for high spatial resolution and a much better capability of distinguishing between objects.
A high-resolution system can determine whether a vehicle will crash into an object or there will be a near miss. A low-resolution system will have a higher rate of false alarms and will miss a small object that is in front of a big one (see Figure 2).
Smaller devices and a single technology for all applications
The structure of high frequency circuits and the size of antennas depend directly on the wavelength used. The higher the operational frequency, the smaller the total size of the radar device. The relationship is linear, with the result that a device operating in the 79 GHz band is smaller by a factor of three than a device using the 24 GHz band.
Currently, automotive radar applications use different frequency ranges for different applications. By using a common 76 GHz to 81 GHz technology platform, a holistic and flexible system can be established. This makes development easier, and individual sensors can be used for multiple purposes.
The European Commission’s 79 GHz project — an initiative towards a worldwide harmonized frequency allocation
Given the benefits of using the 79 GHz band, there is momentum towards a worldwide harmonized frequency allocation for vehicular radars in the frequency range 77 GHz to 81 GHz. Technological progress and advocacy in countries and regions will pave the way for global agreements in ITU’s Radiocommunication Sector and the International Electrotechnical Commission (IEC).
The 79 GHz project founded by the European Commission (www.79ghz.eu) involves specific activities in countries, as well as an expert group — the International Automotive Radio Regulations Expert Group — to speed up global agreement to use the 79 GHz band for vehicular radars.
In 2004, the European Commission legislated on the harmonization of the 79 GHz band for use by short range radar equipment for the European Union member States as well as the European Economic Area (EEA) States (Iceland, Liechtenstein, Switzerland and Norway). In all 27 member States of the European Union, as well as in all the other countries that are members of the European Conference of Postal and Telecommunications Administrations (CEPT), the use of short range vehicular radar operating in the 77 to 81 GHz frequency range is regulated by an ETSI standard (EN 302 264). Vehicular radar equipment transmitting in the 79 GHz band faces neither time constraints nor any other operative restriction burdens, and is thus permitted to operate in the near vicinity of radio astronomy sites (in general, such operation is prohibited).
What other countries are doing
As members of CEPT, Belarus, Georgia, the Russian Federation, Ukraine, Turkey and the Balkan region have approved the use of the 79 GHz band for automotive high-resolution short range radars, with identical provisions as those set by the European Commission and by ETSI standard EN 302 264.
In North America, the United States Federal Communications Commission (FCC) is expected to rule favourably on a petition submitted in May 2012 by Bosch (on behalf of the 79 GHz project) on the use of the 79 GHz band for short range radar in the United States. The Federal Communications Commission would then be expected to release a Notice of Proposed Rule Making, proposing to adopt rules permitting the use of the 77–81 GHz band for automotive radar applications in the United States on an unlicensed basis. In Canada, a similar proposal has been sent to Industry Canada.
In Latin America, Brazil and Argentina are at a preliminary stage of considering the use of the 79 GHz band for vehicular short range radar.
In the Gulf States, Saudi Arabia and the United Arab Emirates are considering implementing the relevant ETSI standard, while in Oman the 79 GHz band has been allocated since 2009 for vehicular short range radar, with the same power limit as in the ETSI standard.
In the Asia-Pacific region, China currently has no regulation for 79 GHz high resolution vehicular radars, although the Hong Kong region is taking steps in that direction. The Republic of Korea’s National Radio Research Agency is preparing to amend legislation to accept 79 GHz. Thailand’s National Broadcasting and Telecommunication Commission is expected to consider the matter. The Malaysian Communications and Multimedia Commission is working on an automotive/ultra-wide band spectrum plan to be included in its Standard Radio System Plan. In India, the 79 GHz band is not regulated. In New Zealand, the Radio Spectrum Management is considering adopting the European Union solution.
Singapore was the first country after the European member States and all other CEPT countries to adopt the 79 GHz band for short range radar (it did so in 2007). Regulations for 79 GHz have already been set up in Australia by the Australian Communications and Media Authority. In Japan, the Ministry of Internal Affairs and Communications has established regulations for 79 GHz band high-resolution radar.
Companies investing in 79 GHz technology
Various projects have been undertaken since the European Decision in 2004 to open the 79 GHz band for automotive short range radar. The Radar on Chips for Cars (RoCC) project involves Daimler, BMW, Bosch, Infineon and Continental (with financing from the German government). The RoCC project aims to further advance silicon-based radar technology in the 76–81 GHz band. Its goal is to bring down the cost of 79 GHz automotive radar sensors significantly and make them cost-competitive. The main cost drivers for 79 GHz sensors are the high frequency laminate and millimetre wave chips required for processing, and the micro-processor itself.
In France, research and development work has also been undertaken on 79 GHz ultra-wideband short range radar technology within the framework of three projects (RADAR ACC, ARPOD and RASSUR 79) financed by the French government, complementing work being carried out by PSA Peugeot Citroën Automobile.
A range of companies have made substantial investments in 79 GHz high-resolution radar technology. Among companies involved in the integration of all types of applications (such as pre-crash or blind spot functions), investors include TRW, Bosch, Continental, Denso and MAGNA. Radar suppliers that are investing include Autocruise (TRW), Fujitsu Ten and Hitachi. Radar millimetre wave chip suppliers such as Freescale, Infineon, UMS, ST Microelectronics and TriQuint are also investors. It seems that the 79 GHz technology is almost ready to be validated and that costs can be kept stable.
Taking an advocacy approach, the International Organization of Motor Vehicle Manufacturers (OICA) and the European Association of Automotive Suppliers (CLEPA) have created a joint task group — the Global Automotive Radio Regulations Expert Group — to promote global frequency harmonization for radiocommunication systems used to equip motor vehicles.
This article is based on contributions from the activities of the partners of the European Commission founded 79 GHz project: Robert Bosch GmbH, TRW, ERTICO — ITS Europe, Continental and Renault.