Power/Performance Bits: July 30

100GHz transceiver
Engineers at the University of California Irvine built a new wireless transceiver that works above 100 gigahertz. The 4.4-millimeter-square silicon chip, called an “end-to-end transmitter-receiver,” uses a digital-analog architecture that modulates the digital bits in the analog and radio-frequency domains to process digital signals quickly and energy-efficiently.

“We call our chip ‘beyond 5G’ because the combined speed and data rate that we can achieve is two orders of magnitude higher than the capability of the new wireless standard,” said Payam Heydari, NCIC Labs director and UCI professor of electrical engineering & computer science. “In addition, operating in a higher frequency means that you and I and everyone else can be given a bigger chunk of the bandwidth offered by carriers.”

Heydari said that in addition to enabling the transmission of signals in the range of 100 gigahertz, the transceiver’s unique layout allows it to consume considerably less energy than current systems at a reduced overall cost, paving the way for widespread adoption in the consumer electronics market.

“The Federal Communications Commission recently opened up new frequency bands above 100 gigahertz,” said postgraduate researcher Hossein Mohammadnezhad, a UCI grad student in electrical engineering & computer science at the time of the work. “Our new transceiver is the first to provide end-to-end capabilities in this part of the spectrum.”

The team’s single-channel 115-135-GHz receiver prototype was fabricated in a 55-nm SiGe BiCMOS process and showed a max conversion gain of 32 dB and a min noise figure (NF) of 10.3 dB. A data rate of 36 Gb/s was wirelessly measured at 30cm distance with total power consumption of 200.25 mW.

In particular, the team sees the transceiver in combination with phased array systems as providing a wireless means of data transfer in the data center, according to Huan Wang, a UCI doctoral student in electrical engineering & computer science. “Our innovation eliminates the need for miles of fiber-optic cables in data centers, so data farm operators can do ultra-fast wireless transfer and save considerable money on hardware, cooling and power.”

TowerJazz and STMicroelectronics provided semiconductor fabrication services to support the research project.

Boosting wearable signals
Researchers at the National University of Singapore and University of Waterloo developed a conductive textile that can be used in clothing to boost the communications power of wearable devices and sensors. The team says such a ‘wireless body sensor network’ allows devices to transmit data with 1,000 times stronger signal, improving device battery life.

Typically, wearable devices use Bluetooth or Wi-Fi to report back to the user’s smartphone. As they broadcast several meters in all directions, energy is lost to the surrounding environment. Instead, when woven into clothing, the team’s metamaterial textile is able to create ‘surface waves’ which can glide wirelessly around the body such that the energy of the signal between devices is held within 10 centimeters of the body rather than spread in all directions.

“This innovation allows for the perfect transmission of data between devices at power levels that are 1,000 times reduced. Or, alternatively, these metamaterial textiles could boost the received signal by 1,000 times which could give you dramatically higher data rates for the same power,” said John Ho, an assistant professor at NUS. Plus, the researchers say the signal between devices is so strong that it is possible to wirelessly transmit power from a smartphone to the device itself, which cloud allow for battery-free wearable devices.

Source: NUS

The textile consists of a comb-shaped strip of metamaterial on top of the clothing with an unpatterned conductor layer underneath. These strips can then be arranged on clothing in any pattern necessary to connect all areas of the body. The metamaterial itself is cost-effective, in the range of a few dollars per meter, and can be bought readily in rolls. The smart clothing is then fabricated by laser-cutting the conductive metamaterial and attaching the strips with fabric adhesive.

Additionally, the metamaterial works with any existing wireless device in the designed frequency band and doesn’t require any changes to the smartphone or wearable device.

“We started with a specific metamaterial that was both flat and could support surface waves. We had to redesign the structure so that it could work at the frequencies used for Bluetooth and Wi-Fi, perform well even when close to the human body, and could be mass produced by cutting sheets of conductive textile,” Ho explained.

The conductive clothing is robust and can withstand folding, bending, washing, drying, and ironing with minimal loss to the signal strength.

Walking energy
Researchers at the Chinese University of Hong Kong developed a wearable energy harvesting device that when attached to the knee can generate 1.6 microwatts of power while the wearer walks. The team says that’s enough to power small health monitoring equipment or GPS devices.

The device uses a macrofiber material that generates energy from any sort of bending it experiences to create a slider-crank mechanism, which is used to transform the rotary motion of the human knee joint to linear motion, which is transformed to a bending motion by a bending beam. The knee was chosen as the location due to the joint’s large range of motion, compared to most other human joints. “These harvesters can harvest energy directly from large deformations,” said Wei-Hsin Liao, professor in the department of mechanical and automation engineering at the Chinese University of Hong Kong.

Due to the continuous back-and-forth the material will encounter when the wearer walks, every time the knee flexes, the device bends and generates electricity. This means the harvester can “capture biomechanical energy through the natural motion of the human knee,” noted Liao.

The prototype weighs 307 grams (0.68 pounds) and was tested on human subjects walking at speeds from 2 to 6.5 kilometers per hour (about 1 to 4 miles per hour). The researchers compared the wearers’ breathing patterns with and without the device and determined that the energy required to walk was unchanged, meaning that the device is generating power with no extra exertion on the human’s part.

The team is looking towards future commercialization of the technology.