UT photonic filter breaks RF dynamic range record

Researchers at the University of Twente (UT) have developed a programmable integrated microwave photonic filter with a record-breaking dynamic range. “Traditional radio frequency filters can only work in a narrow frequency range, meaning you need several separate filters for broadband operation. Our device is integrated, broadband, and has an enormous dynamic range, making it possible to use just a single photonic circuit for various frequency ranges,” explains David Marpaung, chair of UT’s Nonlinear Nanophotonics group.

Before this discovery, programmable microwave photonic circuits with such advanced functions had poor performance. “Versatile programming of the chip can easily give in to various disturbances like loss, noise and distortion of the signal,” says Marpaung. To prevent this, the researchers employ 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.

The researchers also used a special tool – a so-called modulation transformer – to adjust the strength and timing of light waves and RF signals. This enables enhancement of the chip noise and dynamic range performance. By combining these elements in a single microwave photonics circuit, the team could demonstrate programmable filter functions with a record-low noise figure of 15 dB and an RF notch filter with an ultra-high dynamic range of more than 123 dB in 1 Hz bandwidth – a similar range as the noise levels between complete silence and a rock concert.