Microwave photonic I/Q mixer for wideband frequency downconversion with serial electro-optical modulations

In this paper, we propose a serial electro-optical (EO)-modulation-based microwave photonic in-phase and quadrature (I/Q) mixer and investigate its performance for wideband frequency downconversion. The proposed I/Q mixer uses two EO modulators and a programmable optical processor in a serially cascaded structure, which ensures good phase stability and flexibility to achieve high-performance broadband frequency downconversion. A proof-of-concept experiment is carried out in which the frequency downconversion of the RF signals in the range from 10 to 40 GHz is demonstrated with an average image rejection ratio of 38.66 dB. The spurious-free dynamic range (SFDR) measured at around 15 GHz is 86 dBc·Hz^2/3. Based on this microwave photonic I/Q mixer, a broadband radar receiver is established and de-chirping of linearly frequency modulated (LFM) radar echoes with an instantaneous bandwidth of 8 GHz (10-18 GHz) is achieved. The results verify its feasibility for high-performance I/Q mixing in practical applications.