Merging antenna and electronics boosts energy and spectrum efficiency

2 min read

By integrating the design of antenna and electronics, Georgia Tech researchers say they have boosted the energy and spectrum efficiency for a new class of millimetre wave transmitters.

The hope is this will allow for improved modulation and reduced generation of waste heat, meaning longer talk time and higher data rates in millimetre wave wireless communication devices for future 5G applications.

The co-design technique allows simultaneous optimisation of the millimetre wave antennas and electronics, say the researchers. The hybrid devices use conventional materials and IC technology, meaning no changes would be required to manufacture and package them.

According to the team, it also allows fabrication of multiple transmitters and receivers on the same IC chip or the same package, potentially enabling multiple-input-multiple-output (MIMO) systems as well as boosting data rates and link diversity.

“Our electronics and antenna were designed so that they can work together to achieve a unique on-antenna outphasing active load modulation capability that significantly enhances the efficiency of the entire transmitter,” explains assistant professor Hua Wang of Georgia Tech. “This system could replace many types of transmitters in wireless mobile devices, base stations and infrastructure links in data centres.”

“We are combining the output power though a dual-feed loop antenna, and by doing so with our innovation in the antenna and electronics, we can substantially improve the energy efficiency,” continues Wang. “The innovation in this particular design is to merge the antenna and electronics to achieve the so-called outphasing operation that dynamically modulates and optimizes the output voltages and currents of power transistors, so that the millimetre wave transmitter maintains a high energy efficiency both at the peak and average power.

“Within the same channel bandwidth, the proposed transmitter can transmit six to ten times higher data rate,” Wang continued. “Integrating the antenna gives us more degrees of freedom to explore design innovation, something that could not be done before.”

The new designs have been implemented in 45nm CMOS SOI IC devices and flip-chip packaged on high-frequency laminate boards, where testing has confirmed a minimum two-fold increase in energy efficiency, Wang claims.

“An antenna structure with multiple feeds allows us to use multiple electronics to drive the antenna concurrently. Different from conventional single-feed antennas, multi-feed antennas can serve not only as radiating elements, but they can also function as signal processing units that interface among multiple electronic circuits,” Wang explains.

“This opens a completely new design paradigm to have different electronic circuits driving the antenna collectively with different but optimised signal conditions, achieving unprecedented energy efficiency, spectral efficiency and reconfigurability.”

The cross-disciplinary co-design could also facilitate fabrication and operation of multiple transmitters and receivers on the same chip, allowing hundreds or even thousands of elements to work together as a whole system. “In massive MIMO systems, we need to have a lot of transmitters and receivers, so energy efficiency will become even more important,” Wang notes

Having large numbers of elements working together becomes more practical at millimetre wave frequencies because the wavelength reduction means elements can be placed closer together to achieve compact systems, he points out. These factors could pave the way for new types of beamforming that are essential in future millimetre wave 5G systems.

Power demands could drive adoption of the technology for battery-powered devices, but Wang says the technology could also be useful for grid-powered systems such as base stations or wireless connections to replace cables in large data centres. In those applications, expanding data rates and reducing cooling needs could make the new devices attractive.