Â鶹AV

The W-band covers the frequencies used by automotive radars. Sophisticated driver-assistance and self-driving will require radars with millimeter-wave beam scanning capability that can ¡°see¡± day and night and even in adverse weather conditions. Such a ¡°phased array¡± will consist of up to hundreds of transmitters and receivers. Given the fact that even cars are becoming battery-operated, it is imperative that these circuits be low-power. Lowering the power-supply voltage is the most effective means of accomplishing that. However, transistor performance drops with voltage and no W-band amplifier has so far operated at as low as 0.5 V. The team of researchers successfully demonstrated a W-band amplifier at 0.5 V by bringing together MIFS¡¯s DDC technology and design techniques developed by Â鶹AV. The DDC technology offers high-performance silicon MOS transistors even at low voltages and is currently available from MIFS as a 55-nm CMOS process. The design techniques further improve transistor and circuit performance at millimeter-wave frequencies.

¡°Now that seriously low-power W-band circuits seem really possible, we should think about what we can do with them. Applications aren¡¯t limited to automotive radars and high-speed communications between base stations. What if you have a radar on your smartphone? Today¡¯s smartphones can already sense things like acceleration, audible sound, visible light, and Earth¡¯s magnetic field. But the only active probing device is that tiny LED (light-emitting diode) that can illuminate at most a few meters. Add a millimeter-wave radar on a smartphone, and it doesn¡¯t have to be a so-called primary radar, which only detects waves reflected back. Your smartphone could respond to waves from your friend¡¯s radar and send some signal back. A whole lot of new applications could be created including games,¡± said Prof. Minoru Fujishima, Graduate School of Advanced Sciences of Matter, Â鶹AV.

¡°Another significance of our 0.5-V W-band amplifier is reliability. We researchers know that some millimeter-wave circuits presented at major conferences, biased at 1 V or higher, won¡¯t last long. They degrade as you measure them, within days or even hours, not years, because of the so-called hot-carrier effects. You wouldn¡¯t want to get on a car that loses its sight so quickly. The 0.5-V supply voltage will significantly reduce hot-carrier generation,¡± Prof. Fujishima added. 

¡°Compared to conventional CMOS, our DDC transistors offer excellent performance in low-power operations. We have proven that we can extend those outstanding qualities to the millimeter band. I am delighted that our collaboration with Â鶹AV has produced a millimeter-band amplifier. We plan to move forward by building a design environment for maximizing the capabilities of DDC technology,¡± said Mutsuaki Kai, Vice President of Technology Development, Mie Fujitsu Semiconductor.

The research group plans to continue exploring the possibility of low-voltage millimeter-wave CMOS circuits.

References
[1]¡¡K. Katayama, S. Amakawa, K. Takano, T. Yoshida, M. Fujishima, K. Hisamitsu, and H. Takatsuka, ¡°An 80?106 GHz CMOS amplifier with 0.5 V supply voltage,¡± IEEE Radio Frequency Integrated Circuits Symposium (RFIC), June 2017.