Wideband-tunable microwave photonic filter using dissipative self-interference microring resonators

We propose and demonstrate a widely tunable microwave photonic filter with controlled frequency agility, bandwidth reconfigurability and flexible switching functions. It is based on the self-interference microring aided by an asymmetric Mach-Zehnder interferometer, breaking the fundamental microring footprint limit and achieving a doubled free spectral range (123.2 GHz) with a strong out-of-band rejection. Simulation results show that a bandpass microwave photonic filter can be tuned across a 60 GHz frequency range with a varied 3-dB bandwidth from 2.13 GHz to 40.7 GHz in a cascaded dual-ring topology. Its RF out-of-band rejection ratio is improved by more than 60 dB in the high frequency region due to a perfect residual phase cancellation. A dualband notch microwave photonic filter with an extinction ratio of about 50 dB and a frequency tunable range of about 27.7 GHz is also demonstrated, showing its broadly applicability. Our method highlights its suitability to improve chip-scale wideband and high-performance RF receiver systems.