Forging the Future of Sustainable Connectivity: Hyperflexible and Multifunctional RF Filtering Technologies

This article presents a comprehensive overview of the state-of-the-art, design trends, and challenges in the field of highly reconfigurable and co-designed RF/microwave filtering devices. Starting with BPFs with tune-all capabilities in terms of center frequency, BW, TZs, out-of-band rejection profile, and even type of filtering function, their co-integration with other RF functionalities in highly adaptive co-designed circuits are also addressed: e.g., low-noise amplification, phase shifting, attenuation, isolation, and nonmagnetic nonreciprocity by means of STM and transistor-based configurations. Subsequently, the topic of highly adaptive multiband BPF and BSF components for multi-RF-signal-acquisition and multi-RF-interference-suppression tasks is covered. The co-integration of spectrally agile multinotch filtering units with ultrawideband BPFs is also addressed, for which different approaches are shown. Furthermore, other design trends and challenges in this exciting field are briefly discussed. They include 1) advanced co-designed RF filtering modules with selectable multi-BPF/BSF states, 2) electronic tuning in 3D and miniaturized high-Q technologies, 3) self-adaptable and spectrum-aware filters, 4) reconfigurable integrated filters for various applications, such as reflectionless or flattened-passband BPFs or adaptive negative-group-delay multiband RF processors.