Wideband photonic subsampling up to 110 GHz at a 1-GHz sampling rate using a thin-film lithium niobate modulator.

Abstract

The expansion of wireless communications toward carrier frequencies beyond 70 GHz confronts conventional superheterodyne receivers with fundamental challenges, particularly the performance degradation of high-frequency local oscillators (LOs) and mixers. Microwave photonics offers a promising solution for high-frequency signal processing by leveraging the intrinsic bandwidth and low timing jitter of optical devices. In this Letter, we present a photonic subsampling receiver that combines a femtosecond mode-locked laser (MLL) with a repetition rate of approximately 1 GHz and a thin-film lithium niobate (TFLN) modulator with a bandwidth of 110 GHz. Through photonic frequency mixing, optoelectronic conversion, and low-pass filtering, carriers up to 110 GHz are down-converted to a single 0-500 MHz intermediate frequency (IF) band. A commercial low-bandwidth analog-to-digital converter (ADC) then performs the digitization. The system achieves an effective number of bits (ENOB) of 4.1 at 109.99 GHz, with a timing jitter of 6.4 fs. Spurious suppression exceeds 30 dB across the entire measured band without any hardware reconfiguration. This architecture eliminates high-frequency electronic components, offering a potential front-end solution for future millimeter-wave communications.