Abstract
Microwave photonic filters (MPFs) have been suggested as one solution to high-speed tunable wideband radio-frequency (RF) signal processing possessing unique characteristics relative to their all-electronic counterparts (or equivalents), both in bandwidth and tunability and insensitivity to electromagnetic interference. The article is a review of MPF design technologies and applications, and also contains relevant techniques in thermal, electrical and optical tuning as well as new methods founded on stimulated Brillouin scattering, optical frequency combs, and micro-ring resonators. The survey focuses on programmable optical processors, including liquid-crystal-on-silicon designs, arrayed waveguide gratings, and cascaded resonator designs, as arbitrary filters synthesis. Critical consideration is done on performance metrics which include bandwidth, selectivity, out-of-band rejection and tuning range, energy efficiency and other practical factors like stability in the environment and complexity of fabrication. The latest advances in reconfiguration with the help of artificial intelligence and machine learning are presented, and their significance in the optimization of adaptive and predictive filters is also highlighted. The paper also discusses the current constraints such as integration, power consumption, and environmental sensitivity and has provided directions of future achievability of compact, low-power and ultrafast and highly flexible MPFs to next-generation RF communication, radio-over-fiber, and cognitive radio systems. The survey should be used as a source of reference to the researchers and engineers who seek to improve the development, testing, and real-life application of the state of art technologies in the field of microwave photonic filtering.