A new chip-sized microwave photonic filter has been developed by scientists to detach communication signals from noise and curb undesirable interference happening throughout the complete radio frequency spectrum.
Illustration of how the integrated microwave photonic filter helps to separate signals of interest from background noise or unwanted interference in complex electromagnetic environments. Image Credit: Peking University research team
The device is anticipated to assist next-generation wireless communication technologies to convey data efficiently in an environment that is turning out to be crowded with signals from devices like self-driving vehicles, cell phones, smart city infrastructure, and internet-connected appliances.
This new microwave filter chip has the potential to improve wireless communication, such as 6G, leading to faster internet connections, better overall communication experiences, and lower costs and energy consumption for wireless communication systems.
Xingjun Wang, Researcher, Peking University
Wang added, “These advancements would directly and indirectly affect daily life, improving overall quality of life and enabling new experiences in various domains, such as mobility, smart homes, and public spaces.”
In a new study performed, the scientists explain how their new photonic filter defeats the restrictions of conventional electronic devices to achieve several functionalities on a chip-sized device having low power consumption.
Also, they illustrate the potential of the filter to operate throughout a broad radio frequency spectrum that extends to more than 30 GHz. This displays its suitability for visualized 6G technology.
The study was reported in the Photonics Research journal, co-published by Chinese Laser Press and Optica Publishing Group.
As the electro-optic bandwidth of optoelectronic devices continues to increase unstoppably, we believe that the integrated microwave photonics filter will certainly be one of the important solutions for future 6G wireless communications. Only a well-designed integrated microwave photonics link can achieve low cost, low power consumption, and superior filtering performance.
Xingjun Wang, Researcher, Peking University
Stopping Interference
The reason behind the development of 6G technology is to improve upon currently deployed 5G communications networks. For more data to be conveyed at a faster rate, 6G networks are anticipated to utilize millimeter wave and even terahertz frequency bands.
Since this will spread signals over an extremely wide frequency spectrum with a high data rate, there is a high probability of interference between various communication channels.
For this issue to be resolved, scientists have intended to come up with a filter that could safeguard signal receivers from several kinds of interference throughout the full radio frequency spectrum.
To be affordable and practical for extensive deployment, it is significant for this filter to be compact, use little power, achieve several filtering functions, and be able to be integrated into a chip. But earlier demonstrations have been restricted by their large size, few functions, limited bandwidth, or needs linked to electrical components.
For the new filter, scientists made a streamlined photonic architecture consisting of four main parts. Initially, a phase modulator acts as the input of the radio frequency signal, which adjusts the electrical signal onto the optical domain.
Then, to shape the modulation format, a double-ring acts as a switch. An adjustable microring is known to be the core unit for processing the signal. Eventually, a photodetector acts as the output of the radio frequency signal and retrieves the radio frequency signal from the optical signal.
The greatest innovation here is breaking the barriers between devices and achieving mutual collaboration between them. The collaborative operation of the double-ring and microring enables the realization of the intensity-consistent single-stage-adjustable cascaded-microring (ICSSA-CM) architecture.
Xingjun Wang, Researcher, Peking University
Wang added, “Owing to the high reconfigurability of the proposed ICSSA-CM, no extra radio frequency device is needed for the construction of various filtering functions, which simplifies the whole system composition.”
Demonstrating Performance
For the device to be tested, scientists make use of high-frequency probes to load a radio frequency signal into the chip and gather the recovered signal with a high-speed photodetector.
They made use of directional antennas and arbitrary waveform generators to simulate the generation of 2 Gb/second high-speed wireless transmission signals and a high-speed oscilloscope for the processed signal to be received. The scientists were able to illustrate the performance of the filter by making a comparison of the outcomes with and without the use of the filter.
On the whole, the outcomes show that the simplified photonic architecture attains comparable performance with system complexity and lower loss than with earlier programmable integrated microwave photonic filters made of hundreds of repeating units. This makes it highly strong, more energy-efficient, and simpler to manufacture compared to earlier devices.
The scientists plan to additionally improve the modulator and enhance the entire filter architecture to obtain a high dynamic range and low noise while high integration at both the device and system levels has been guaranteed.
Journal Reference
Tao, Z., et al. (2023) Highly reconfigurable silicon integrated microwave photonic filter towards next-generation wireless communication. Photonics Research. https://doi.org/10.1364/PRJ.476466.