A team of researchers has created a new chip-sized microwave photonic filter that can effectively separate communication signals from noise and suppress unwanted interference across the entire radio frequency spectrum. This development is expected to benefit next-gen wireless communication technologies, enabling them to transmit data more efficiently in an environment that is becoming increasingly crowded with signals from various devices like cell phones, smart city infrastructure, self-driving vehicles, and internet-connected appliances.
According to Xingjun Wang, a researcher at Peking University, “This new microwave filter chip has the potential to revolutionize wireless communication, including 6G, resulting in faster internet speeds, improved communication experiences, and reduced costs and energy consumption for wireless communication systems. These improvements will have a direct and indirect impact on everyday life, enhancing the overall quality of life and enabling new experiences across various domains such as mobility, smart homes, and public spaces.”
The researchers detail their new photonic filter in the Photonics Research journal, highlighting how it surpasses the limitations of traditional electronic devices to achieve multiple functions on a chip-sized device with low power consumption. They also demonstrate the filter’s ability to operate across a broad radio frequency spectrum extending to over 30 GHz, making it ideal for 6G technology.
Wang further stated, “With the electro-optic bandwidth of optoelectronic devices continuing to increase rapidly, we believe that the integrated microwave photonics filter will be a crucial solution for future 6G wireless communications. Only a well-designed integrated microwave photonics link can achieve low cost, low power consumption, and superior filtering performance.”
The development of 6G technology aims to enhance the current 5G networks by enabling faster transmission of more data through the use of millimeter wave and terahertz frequency bands. However, due to the extremely wide frequency spectrum and high data rate of 6G networks, interference between different communication channels is highly likely.
To address this issue, researchers have worked on creating a filter that can effectively protect signal receivers from various types of interference across the full radio frequency spectrum. The filter needs to be small, consume minimal power, provide multiple filtering functions, and be cost-effective for practical deployment. Past demonstrations have been limited in bandwidth, size, or electrical component requirements.
The new filter design features a simplified photonic architecture consisting of four primary parts. A phase modulator serves as the input of the radio frequency signal, with a double-ring acting as a switch to shape the modulation format. An adjustable microring functions as the core unit for processing the signal, while a photodetector serves as the output of the radio frequency signal and recovers it from the optical signal.
“The major innovation lies in breaking down the barriers between devices and enabling their mutual collaboration,” commented 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. Due to the high reconfigurability of the proposed ICSSA-CM, no extra radio frequency device is needed for the construction of various filtering functions, simplifying the whole system composition.”
The device was tested by researchers who utilized high-frequency probes to load a radio frequency signal into the chip, and then collected the recovered signal using a high-speed photodetector. To simulate the generation of 2Gb/s high-speed wireless transmission signals, an arbitrary waveform generator and directional antennas were employed, with a high-speed oscilloscope used to receive the processed signal. By comparing results with and without the filter, the researchers demonstrated the filter’s effectiveness.
The findings reveal that the simplified photonic architecture performs comparably with lower loss and system complexity than previous programmable integrated microwave photonic filters, which consisted of hundreds of repeating units. This makes it more robust, energy-efficient, and easier to manufacture than previous devices.
Further optimization of the modulator and improvement of the overall filter architecture are the researchers’ next steps, with the goal of achieving a high dynamic range and low noise while ensuring high integration at both device and system levels.