Integrated thin-film lithium niobate microwave photonic mixer for 6G broadband wireless communications

Microwave frequency conversion, fundamental to radar and wireless communications, faces inherent limitations in bandwidth, noise, and reconfigurability within traditional electronic architectures. This work addresses these challenges by demonstrating a fully integrated microwave photonic frequency converter on a thin-film lithium niobate platform. The proposed device merges parallel electro-optic modulation and in-situ phase tuning in a monolithic chip, enabling software-defined filter-free broadband frequency translation from 10 MHz to 40 GHz (demonstrated over the measured RF/LO range) with image rejection > 50 dB and a spurious–free dynamic range of 95.58 dB·Hz 2/3 @10 GHz. To validate its capability for future communication systems, we conduct two system–level experiments. First, with a 10 GHz local oscillator and RF input sweeping from 12 to 26 GHz, the mixer achieves a conversion–gain variation below 3.7 dB and a down–conversion frequency accuracy within ± 3 MHz over the entire 2–16 GHz IF band. Second, a 500–Mbaud QPSK signal at 4 GHz is mixed with a 5 GHz tone using the on–chip dual–parallel Mach–Zehnder modulator, simultaneously yielding up–converted (9 GHz) and down–converted (1 GHz) QPSK outputs. Directly demodulated without any digital pre–distortion or equalization, the error vector magnitudes are 25.3 % and 32.6 %, respectively, versus 14.3 % for the original signal. These results, together with the device’s reconfigurability and wideband operation, highlight the potential of thin–film lithium niobate integrated mixers for emerging 6G wireless systems, wideband phased–array radars, and software–defined radio front–ends.