As data connectivity needs increase, efficient communication through beamforming arrays becomes important. However, the use of delay elements in these arrays poses challenges such as limitations on size, channel capacity, power efficiency, and adequate radiated power.
Passive phase shifters do not consume DC power, but have limitations such as narrow bandwidth, low phase resolution, and low power handling capabilities. It also causes beam squint, where different frequency components are delayed, blurring the signal and reducing resolution.
To address these issues, a true time delay (TTD) element was introduced. Although they offer a wide-bandwidth solution, their size makes them inefficient for modern semiconductor processes, as they require wavelength-scale transmission lines.
Researchers at Cornell University have developed a semiconductor chip that adds the necessary time delay so that signals sent across multiple arrays can align to a single point in space without collapsing. This approach will allow ever smaller devices to operate at the higher frequencies required for future 6G communications technology.
“We’re excited to announce that this is the first time we’ve found a solution to this problem,” said senior author Alyssa Apsell, IBM professor of engineering and chair of the electrical and computer engineering department at Cornell Engineering. “Every frequency in a communications band has a different time delay. The problem we are addressing is decades old, and is one that allows high-bandwidth data to be transmitted economically and across all frequencies. signals at the right place and time.”
“We’re excited to announce that this is the first time we’ve found a solution to this problem,” said senior author Alyssa Apsell, IBM professor of engineering and chair of the electrical and computer engineering department at Cornell Engineering. “It’s not just about building something with enough delay, it’s about building something with enough delay that the signal remains at the end. The trick is that you can do it without big losses. about it.”
Previously, phase-shift circuits were used to achieve time delays. Still, there were limitations, especially for broadband signals, as different frequencies could get out of sync, causing blurring known as “beam strabismus.” Making the delay time small enough to fit smartphones was a big challenge.
To address this problem, researchers designed a new chip using complementary metal oxide semiconductor (CMOS) technology. The chip can adjust time delays with high precision over a wide bandwidth of 14 GHz.
Instead of using long wires for delays, they devised a clever method. They created a 3D reflector that reflects the signal and causes a delay. These reflectors were linked together to form an “adjustable transmission line”, allowing for flexible and precise time delays.
The new integrated circuit is very impressive, and despite being smaller than a phase shifter, it significantly increases channel capacity and nearly doubles the data rate of traditional wireless arrays. This means we can deliver data faster and provide faster service to mobile phone users.
Reference magazines:
- Govind, B., Tapen, T., Apsel, A. Ultra-compact quasi-true time delay for enhancing wireless channel capacity. Nature 627, 88–94 (2024). DOI: 1038/s41586-024-07075-y
