In order to extract communication signals from background noise and minimize undesirable interference over the whole radio frequency spectrum, researchers have created a novel chip-sized microwave photonic filter.
The gadget is anticipated to assist next-generation wireless communication technologies in efficiently transmitting data in a space that is growing crowded with signals from gadgets like cell phones, self-driving cars, internet-connected appliances, and smart city infrastructure.
“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,” said researcher Xingjun Wang from Peking University. “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 the Photonics Research journal co-published by Chinese Laser Press and Optica Publishing Group, the researchers describe how their new photonic filter overcomes the limitations of traditional electronic devices to achieve multiple functionalities on a chip-sized device with low power consumption.
They also show that the filter can function over a wide radio frequency spectrum that reaches over 30 GHz, demonstrating its applicability for the 6G technology that is anticipated.
“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,” said Wang. “Only a well-designed integrated microwave photonics link can achieve low cost, low power consumption and superior filtering performance.”
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. 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.
Xingjun Wang
Stopping interference
To outperform the 5G communication networks now in use, 6G technology is being developed. 6G networks are anticipated to utilise millimeter wave and potentially terahertz frequency bands in order to transmit more data more quickly. As a result of the increased data rate and exceptionally wide frequency distribution of the signals, there is a significant chance that several communication channels will interfere with one another.
To address this issue, scientists have worked to create a filter that can shield signal receivers over the whole radio frequency spectrum from different kinds of interference. This filter must be tiny, use little power, perform numerous filtering functions, and be able to be integrated on a chip in order to be affordable and feasible for wide-scale deployment. Previous demonstrations, however, had limitations because to their few functionality, size, bandwidth, or electrical component requirements.
For the new filter, researchers created a simplified photonic architecture with four main parts. The radio frequency signal is first supplied into a phase modulator, which modulates the electrical signal onto the optical domain.
After that, a double-ring switches the modulation format. The main component for signal processing is an adjustable microring. The output of the radio frequency signal is a photodetector, which separates the radio frequency signal from the optical signal.
“The greatest innovation here is breaking the barriers between devices and achieving mutual collaboration between them,” said Wang. “The collaborative operation of the double-ring and microring enables the realization of the intensity-consistent single-stage-adjustable cascaded-microring (ICSSA-CM) architecture. 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
The gadget was tested using high-frequency probes to load a radio frequency signal into the chip and a high-speed photodetector to extract the signal. To replicate the creation of 2Gb/s high-speed wireless transmission signals, they used an arbitrary waveform generator, directional antennas, and high-speed oscilloscopes.
By comparing the results with and without the use of the filter, the researchers were able to demonstrate the filter’s performance.
Overall, the results demonstrate that, compared to earlier programmable integrated microwave photonic filters made up of hundreds of repeating units, the reduced photonic design provides equivalent performance with lower loss and system complexity. Because of this, it is more durable, energy-efficient, and simpler to construct than earlier gadgets.
To obtain a large dynamic range and low noise while assuring good integration at both the device and system levels, the researchers intend to further refine the modulator and enhance the overall filter architecture.
