Autonomously Tunable Filters for Interference Mitigation: Advances in Autonomously Switchable/Tunable RF/Microwave Filters for Interference Mitigation Without Operator Intervention

In wireless communication, there is a strong demand for tunable filters in scenarios that require adaptively coping with multiband interference in RF front ends. Tuning devices, ferroelectric capacitors, ferromagnetic-material-based devices, microelectromechanical systems capacitors, and piezoelectric-material-based devices are commonly used for center frequency tuning or bandwidth adjustment in tunable filter realizations. Tunable or switchable filters are essential for this desired adaptability. However, each type has thus far demonstrated its particular disadvantages. Typically, continuously tunable filters are difficult to design or require intensive use of resources to control accurately, while switchable filter banks have significant insertion loss from switching networks. Tuning capability in tunable filters often requires human intervention to control tuning frequencies or bandwidths. In this article, we introduce autonomously tunable filters to adaptively protect or mitigate receiver systems from unwanted or unreferenced signals in RF front ends using an RF-power-dependent coupling without extra control signals or closed-loop feedback of digital processing of the spectrum through analog-to-digital and digital-to-analog converters.