Integrated TFLN electro-optic field probe for single-shot dual-band radio-frequency spectrum monitoring via photonic undersampling

Demonstrating a photonic front-end for single-shot dual-band millimeter-wave (mmWave) spectrum awareness, this work co-integrates a monolithic thin-film lithium niobate (TFLN) electro-optic field probe with a photonic undersampling receiver. The probe features a dual-band antenna and a Mach-Zehnder modulator for in-situ mmWave-to-optical conversion. Photonic sampling using a 5-GHz optical pulse train in the probe simultaneously maps two widely separated mmWave bands (27.6-28.4 GHz and 58.5-59.9 GHz) into non-overlapping intermediate-frequency (IF) windows (1.6-2.4 GHz and 0.1-1.5 GHz) via a single photodiode for digitization. The system achieves single-shot spectral reconstruction with 1 kHz fidelity and phase-coherent 256QAM signal reception at 28 GHz (3.5% EVM), with field sensitivities of 2.7 and 8.1 mV/m/Hz at 28 GHz and 59 GHz, respectively. By transferring the burden of multiband operation from broadband RF hardware to scalable photonic mapping and digital signal processing, this scheme enables compact, power-efficient distributed real-time spectrum situational awareness.