Researchers in Singapore have created a device capable of manipulating radio frequency signals that could lead to the development of smaller short-distance communication systems.
Known as a subharmonic passive mixer, the device, built by Rui Li and her colleagues at the A*STAR Institute of Microelectronics, can convert millimeter waves from one wavelength to another. Millimeter waves are a type of high frequency electromagnetic radiation with wavelengths between 0.1 and 10 millimeters long. Because they are susceptible to absorption by water in the atmosphere, the can only travel short distances, and so are often used in short-range, secure wireless communication, radio astronomy and automotive-radar technology, which allows self-driving cars to sense their surrounding environment,
According to the researchers, the device mixes an incoming millimeter wave that has a wavelength of 2.2 millimeters with a local source of 4.3-millimeter waves to generate a 1.1-millimeter signal. A signal of this wavelength, says the research team, means that the device operates at a frequency of 273 GHz, a high frequency that allows for a large number of potential transmission channels.
The device is the first example of a system-on-package (SOP) converter operating at such a high frequency, says Li. SOP is an emerging microelectronic technology that places computing, communication and consumer functions—such as processor, memory, graphics, antennas, filters, switches, optical waveguides and other components required to form a system—on a single chip. The SOP approach is perceived by many to enable lower-cost, more efficient and higher performance electronic systems because it overcomes the fundamental and integration shortcomings of system-on-chip (SOC) and system-in-package (SIP) approaches, which are limited by CMOS processing.
Li and her colleagues also addressed the use of silicone in their new device. While silicon is often the material of choice for use in both SOCs and SIPs, its low electrical resistance can often cause an energy loss that degrades the overall system performance. The new device is instead comprised of stacked thin films of metal separated by benzocyclobutene, a polymer with good electrical performance, even in the millimeter-wave region.
“We are currently in the process of designing and implementing numerous similar types of millimeter-wave passive components in various types of packages,” Li said. “We hope this will reduce the chip area as compared to ‘on-chip’-based approaches.”
