Clear way for more wireless comms channels
Researchers in Peking have designed photonic filters for 6G signals that minimise ‘noise waste’ and maximise use of the spectrum, giving Chinese kit manufacturers far superior options for building the next generation of wireless comms. The invention hinges on a key breakthrough, a new chip-sized microwave photonic filter (pictured) that separates comms signals from noise and suppresses unwanted interference across the full radio frequency spectrum. This means the next-generation of wireless will broadcast data with greater efficiency even as signals from phones, cars and billions of IoTs devices crowd the smart city network with trillions of gigabytes of signals.
The report in Washington based Optica magazine describes how new microwave filter chip could make 6G faster and fitter, packed closely with data on infinitely better regimented arrays along the spectrum. Chinese developers of the technology could create faster internet connections and better comms experiences for lower capital and operational costs, as production is cheaper and energy consumption is minimised. There would also be sharper, better organised structure of domains, such as mobility, smart homes and public spaces, according to researcher Xingjun Wang from Peking University.
A photonic filter overcomes the limitations of traditional electronic devices to achieve multiple functionalities on a chip-sized device with low power consumption. The filter can operate across a broad radio frequency spectrum extending to over 30 GHz, making it suitable for bringing the best out of 6G technology.
The electro-optic bandwidth of optoelectronic devices is currently on an unstoppable upward surge without hitting any barriers, so the integrated microwave photonics filter will be one of the key developments 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.”
If Western companies continue to eschew Chinese technology, this is an area they must study to catch up, presumably, as our vendors strive to stand 6G technology on the shoulders of their 5G comms networks. To convey more data at a faster rate, 6G networks must use millimeter wave and even terahertz frequency bands. As this will distribute signals over an extremely wide frequency spectrum with increased data rate, but there is a high likelihood of interference between different comms channels.
To solve this problem, researchers made a ‘filter’ that can protect signal receivers from various types of interference across the full radio frequency spectrum. To be practical this filter must be small and consume minimal power while maximising the number of filtering functions that can be squeezed onto a chip. Previous attempts only succeeded in placing few functions that were large and achieved only limited bandwidth. Either that or they needed extra electrical components.
In the new filter, researchers devised a simplified photonic design with four main parts. First, a phase modulator serves as the input of the radio frequency signal, which modulates the electrical signal onto the optical domain. Next, a double-ring acts as a switch to shape the modulation format. An adjustable micro-ring is the core unit for processing the signal. Finally, a photodetector serves as the output of the radio frequency signal and recovers 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 micro-ring creates an intensity-consistent single-stage-adjustable cascaded-micro-ring (ICSSA-CM) design. The proposed ICSSA-CM is highly configurable so that careful moderators can ensure that no extra radio frequency device is needed, whatever the number of filtering functions they want to create, which simplifies the whole system’s composition, according to the Peking University research team.
To test the device, researchers used high-frequency probes to load a radio frequency signal into the chip and collected the recovered signal with a high-speed photodetector. They used an arbitrary waveform generator and directional antennas to simulate the generation of 2Gb/s high-speed wireless transmission signals and a high-speed oscilloscope to receive the processed signal. By comparing the results with and without the use of the filter, the researchers were able to demonstrate the filter’s performance.
Overall, the findings show that the simplified photonic architecture achieves comparable performance with lower loss and system complexity compared with previous programmable integrated microwave photonic filters composed of hundreds of repeating units. This makes it more robust, more energy-efficient and easier to manufacture than previous devices.
The researchers plan to further optimise the modulator and improve the overall filter architecture to achieve a high dynamic range and low noise while ensuring high integration at both the device and system levels. Leadership in the next generation of wireless comms hinges on the talent for making Highly reconfigurable silicon says the article in Photonics Research, which disseminates fundamental and applied research progress in optics and photonics. It is led by Editor-in-Chief Lan Yang, Washington University in St. Louis, USA.