Real-time broadband RF signal processing on a photonic chip using bandwidth stretching technology

Over the past three decades, the ever-faster wireless networks have been a key driver of enhanced connectivity across human society, enabling the routine use of high-resolution video streaming, web conferencing, and smartphone APPs today. With 5G networks recently becoming commercially available, the race for 6G has already commenced, promising not only even higher data rates but also more precise environmental sensing through Integrated Sensing and Communication (ISAC) networks. However, real-time processing of high-frequency, wideband radio-frequency (RF) signals, essential for these future networks, poses a significant challenge for traditional RF technologies due to exacerbated transmission losses at high frequencies and gain-bandwidth trade-offsin analog devices. Microwave photonics offers a compelling solution by shifting signal processing tasks from electronic to optical domain. This leverages the inherent advantages of photonic systems, including large bandwidths, flat frequency responses, and immunity to electromagnetic interference. Recent advancements in bandwidth-stretching technology have further enabled high-resolution microwave photonic signal processing by channelizing and mapping a gigahertz RF signal simultaneously to multiple opticalcarriers, effectively expanding the spectral bandwidth to several terahertz. However, current bandwidth-stretched microwave photonic processors are all constructed using discrete optoelectronic devices, with significant disadvantages in terms of size, weight, and power consumption (SWaP). Moreover, they lack the ability to process ultrawideband RF signals required for a 6G ISAC scenario due to the bandwidth limitations of discrete electro-optic modulators. To address these pressing challenges, we propose to develop advanced chip-scale thinfilm lithium niobate (TFLN) photonic circuits that can perform channelized processing and reception of ultrawideband millimeter-wave signals. Our approach involves the large-scale photonic integration of a flat-top electro-optic frequency comb source, a broadband millimeter-wave optic modulator, and a Vernier optical filter, all on the same TFLN chip. This enables compact and low-cost realization of bandwidth-stretched signal processing with broad bandwidths, rapid acquisition speeds, and high resolutions.The technology will be accompanied by proof-of-concept demonstrations of a broadband channelized RF receiver capable of handling 5/6G wireless communications and millimeter-wave radar signals simultaneously, and an ultrafast broadband millimeterwavespectrum analyzer. The proposed research is supported by the expertise,