Automotive millimeter-wave radar accelerates towards the CMOS era

Interview with Dr. Jiashu Chen, CEO of Calterah Microelectronics

Compared with lidar, cameras and other sensors, millimeter-wave radar has all-weather and all-day detection capabilities and can still work normally even in harsh environmental conditions such as rain, snow, dust and fog. In addition, by directly measuring distance and speed, it is easier to detect the target's motion state. Therefore, it is gradually being installed on more and more new cars.

Taking 77 GHz millimeter-wave radar as an example, according to statistics from Gaogong Intelligent Automobile Research Institute, a total of 2.0165 million forward-facing 77GHz millimeter-wave radars were installed in new cars in China in the first half of this year, an increase of 29.36% compared with the same period in 2019. With the launch of new cars equipped with ADAS functions in the second half of the year, it is expected that the year-on-year growth rate of forward-facing 77GHz millimeter-wave radars will remain at 30-40% throughout this year.

Despite this, compared to the entire automotive market, the installation rate of millimeter-wave radar is still low, and how to further promote the popularization of this technology in the automotive field is an urgent problem to be solved. In this regard, Gasgoo recently interviewed Dr. Chen Jiashu, CEO of Calterah Microelectronics. Calterah Microelectronics took the lead in launching the world's first 77GHz CMOS process millimeter-wave radar chip in 2017 and achieved mass production, which led to major changes in the industrial chain. Chen Jiashu pointed out that in order to make millimeter-wave radar a technology that can be used in all levels of vehicles, further breakthroughs in performance, cost and other aspects are needed, and millimeter-wave radar chips will play a very critical role in this. In particular, millimeter-wave radar chips based on CMOS technology are gradually becoming the choice of more and more vehicle manufacturers and parts suppliers because they can help millimeter-wave radars achieve multiple advantages such as high performance, easy development, miniaturization and economy at the same time.

Dr. Jiashu Chen, CEO of Calterah Microelectronics

Miniaturization and economy are the keys to making millimeter-wave radar truly popular

Millimeter-wave radar has been used in the automotive field for a long time. However, the core chips in early millimeter-wave radars mainly used compound semiconductors such as GaAs and SiGe. The front end of millimeter-wave radar chips based on GaAs technology is mostly discrete, that is, the transmitter, receiver and processing components are all independent units, which makes the radar design process very complicated and the product size is often large.

In addition, due to the high prices of the above raw materials, the overall price of millimeter-wave radar is also relatively high, especially 77GHz millimeter-wave radar. Therefore, for a long time in the past, millimeter-wave radar was mainly exclusive to high-end European and American models.

With many years of experience in developing millimeter wave integrated circuits, Chen Jiashu believes that the application prospects of millimeter wave radar in the automotive field are far more than that, especially in the future of assisted driving - as long as the sensor is small enough and economical enough. It was 2014, and in his own words, "at that time, automatic and assisted driving were not as popular as they are now. Whether it was the vehicle manufacturers or the first-tier suppliers, there was no particularly clear strategic direction in these areas." But he decided to give it a try to promote the real popularization of sensors.

Chen Jiashu's idea is to use a completely different CMOS process to replace the relatively expensive compound semiconductor process, thereby reducing the price of millimeter-wave radar. "CMOS technology has been very mature in the field of consumer electronics. For example, WiFi and Bluetooth in mobile phones and processors in computers are all realized using CMOS technology. Compared with compound semiconductors, this technology has a larger economic scale. If millimeter-wave radar chips can also enjoy the scale benefits brought by this CMOS process, the price can be greatly reduced." Chen Jiashu said.

Comparison of RF front-end modules using different processes. Image source: Calterah Microelectronics

To this end, Calterah has launched AiP (Antenna Integrated in Package), which integrates the antenna array inside the chip package to reduce customers' antenna design and high-frequency board investment, and significantly shorten the module R&D and production cycle, accelerating the popularization of millimeter-wave radar in the automotive and industrial markets.

"After customers get this product, they don't even need to design the antenna. In addition to the electronic part, the antenna is the most difficult and costly part of the radar, and the yield control is complex. The launch of this product has greatly reduced the development difficulty for customers." Chen Jiashu said. "And because the antenna is integrated into the chip package, it has been further improved in terms of ease of use and reducing the size of the radar module."

Although CMOS technology has obvious advantages over traditional compound semiconductors in terms of economy, integration, scalability, etc., it is not easy to develop millimeter-wave radar products that truly meet automotive-grade requirements based on this technology.

Chen Jiashu pointed out that "the biggest challenge for companies in the automotive field is how to use CMOS technology to realize high-frequency circuits such as 77GHz and ensure that the noise is within a controllable range." Previously, due to the failure to achieve technological breakthroughs, the industry has not made much progress in the popularization of 77GHz millimeter-wave radar.

"In particular, it must meet the requirements of automobile development. For example, the operating temperature range of the chip must be able to cover -40℃~125℃, and it must be guaranteed that the chip can work normally in such a wide temperature range throughout the entire life cycle of the car. The overall reliability requirements are very high." In addition, functional safety is also a very important aspect. The most important role of functional safety is to ensure that any random failure, system failure or common cause failure will not cause the failure of the safety system, avoiding personal injury or death, environmental damage, equipment and property losses, etc.

In order to better meet the high safety requirements of automakers, Caltland has always put product functional safety management and certification work first to ensure product reliability and safety. In March this year, Caltland successfully passed the ISO 26262 functional safety process management certification of TÜV Rheinland, Germany, and can support ASIL D-level chip development. It is reported that Caltland is currently the only chip design company in the domestic semiconductor industry to obtain this certification. Chen Jiashu said that Caltland will continue to increase investment in the future to strengthen the functional safety of its products.

ISO 26262 Functional Safety Management Certificate, Image source: Calterah Microelectronics

From transceiver, SoC to AiP solutions, multi-faceted support for millimeter-wave radar mass production

It took Gatland three years to develop and mass produce the first generation of its product, Yosemite. "It was a small milestone. When we launched the first generation of CMOS chips in 2017, it was also the world's first automotive-grade CMOS process 77GHz millimeter-wave radar RF front-end chip," said Chen Jiashu.

In the first generation of products, Caltland used a single CMOS chip to realize the millimeter wave RF transceiver chip. Before that, according to the industry's usual practice, multiple compound semiconductors were needed to achieve the same effect. This made the size smaller, and the price of millimeter wave radar naturally dropped. The product officially began to be installed on related models of Chery, SAIC and other brands in 2018, and was used for blind spot monitoring, lane change assistance, forward collision warning, etc.

Soon after, Caltland launched its second-generation product, Alps, in 2019. Compared with Yosemite, Alps implements the analog, digital, and radar algorithms in millimeter-wave radars with a single chip, which is more integrated than the first generation, and has further improved performance, cost, power consumption, etc. It is particularly important to point out the cascading between chips. Through this technology, Caltland can achieve synchronous signal transmission and digital processing signal interaction between multiple chips, thereby effectively expanding the number of chip channels and optimizing product performance. This is also Caltland's original technology.

The radar baseband processing engine embedded in the chip is a very important advantage that distinguishes Calterah from its competitors. This allows customers to quickly develop radar systems simply by configuring registers. "The benefits of this are, first, faster time to market; second, reduced customer resource investment; and third, reduced overall system development costs."

Taking Alps as an example, it takes about 4 to 5 years for traditional chip products to be developed and applied to mass-produced vehicles, but based on Calterah's technology and solutions, it only takes about 3 years to be "applied to vehicles", which greatly shortens the mass production process of millimeter-wave radars and even the launch cycle of complete vehicles. Because of this, although Alps is still in the small-scale production stage, more and more companies are using this chip for millimeter-wave radar research and development.

Through the innovation and rapid iteration of its products, Caltland has actually broken the long-term monopoly of foreign chip giants in the field of automotive millimeter-wave radar. Previously, due to the lack of core technology, domestic millimeter-wave radar, including related chip fields, has been firmly dominated by foreign component giants. Chen Jiashu pointed out that by the end of this year, Caltland will complete Alps's certification in terms of vehicle regulations, reliability, functional safety, etc., and the second-generation product will be available in vehicles as early as early next year.