Microwave Photonic Filter Shifts Paradigm for Future Communications

Researchers from the University of Twente have developed a multifunctional photonic integrated circuit (PIC) that enables programmable filtering functions with a reported record-high dynamic range. The advancement addresses concepts and technologies that include integration, versatile programmability, and techniques for enhancing key radio frequency performance metrics, such as the noise figure.

Though prior R&D in microwave photonics has targeted improvements to these aspects, the researchers said, the recent work introduces an approach to do so simultaneously in a single circuit.

The breakthrough will help the adoption of microwave photonic systems in real applications — such as 6G communication systems and satellite communications, said David Marpaung, an author of the study and chair of the nonlinear nanophotonics group at the University of Twente.

“Our work breaks the conventional and fragmented approach of integration, functionality, and performance that currently prevents the adoption of these photonic systems in real applications,” Marpuang said. “Traditional radio frequency filters can only work in a narrow frequency range, meaning you need several separate filters for broadband operation.”

The device makes it possible to use only a single circuit for various frequency ranges, he said.

Researchers David Marpuang (right) and Okky Daulay developed a programmable integrated microwave photonic filter that could be used in modern radio frequency and microwave applications. The researchers’ architecture allows integration and versatile programmability — as well as techniques for enhancing radio frequency performance metrics, such as the noise figure — to occur simultaneously on a single circuit. Courtesy of University of Twente.

The research showed that the filter component can play a key role in modern radio frequency and microwave applications, including cognitive radio, multiband all-spectrum communications, and broadband programmable front ends. Before the recent discovery, programmable microwave photonic circuits with such advanced functions demonstrated poor performance.

“Versatile programming of the chip can easily give in to various disturbances like loss, noise, and distortion of the signal,” Marpaung said.

The researchers used programmable resonators and interferometers to reduce the impact of noise and nonlinear distortion together, while at the same time providing a large number of filtering functions. Using a modulation transformer to adjust the strength and timing of lightwaves and radio frequency signals, they enhanced the chip noise and dynamic range performance.

By combining these elements in a single microwave photonics circuit, the team demonstrated programmable filter functions with a noise figure of 15 dB and a radio frequency notch filter with an ultrahigh dynamic range of more than 123 dB in 1-Hz bandwidth — a similar noise-level range between complete silence and a rock concert.

The research was published in Nature Communications (www.doi.org/10.1038/s41467-022-35485-x).