Millimeter-wave radars covering several tens of meters could be on cars, bikes and smartphones. (Source: Hiroshima University)Researchers at Hiroshima University and Mie Fujitsu Semiconductor Limited (MIFS) have developed a new low-power millimeter-wave amplifier that could change the safety of self-driving and driver-assisted vehicles. This new amplifier feeds on a 0.5 volt power supply. It also covers a frequency range from 80 to 106 gigahertz. This was developed using MIFS’s Deeply Depleted Channel (DDC) technology.
The W-band covers frequencies that are used by automotive radars. New technologies like driver-assistance and self-driving cars require radars that have millimeter-wave beam scanning ability. This allows the cars to “see” the difference between day and night, even in harsh weather. This phased array consists of hundreds of transmitters and receivers. With the rise in battery-powered cars, it is important for car circuits to be low power. The most effective way to achieve this is to lower the power-supply voltage. It seems simple enough, but when the power-supply voltage is lowered, the transistor performance also drops and no W-band amplifier tested so far has been able to operate at 0.5 volts. This is, until this new research emerged from MIFS and Hiroshima University. Researchers were able to demonstrate successful operation of a W-band amplifier at 0.5 volt using MIFS’s DDC technology and Hiroshima University’s new design techniques. The DDC technology provides high-performance silicon MOS transistors, even at low voltages. The technology is available from MIFS as a 55-nanometer complementary metal-oxide-semiconductor (CMOS) process. The new design techniques allow further improvements to the transistor, as well as 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 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, Hiroshima University.
"Another significance of our 0.5-volt W-band amplifier is reliability. We researchers know that some millimeter-wave circuits presented at major conferences, biased at 1 volt 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-volt supply voltage will significantly reduce hot-carrier generation," Prof. Fujishima added.
The researchers plan to continue exploring the possibility of low- voltage millimeter-wave CMOS circuits. The research is being presented from June 4 to June 6 at the IEEE Radio Frequency Integrated Circuits Symposium (RFIC) 2017 in Honolulu, Hawaii.
