Suppressing in-band interference: A compact lumped-element bandpass filter with adaptive in-band interference suppression capabilities

Because of today?s exceedingly crowded radio spectrum, in which multiple sources of dynamic interference can desensitize a radio's receiver, the design of bandpass filters (BPFs) with adjustable transfer function characteristics has become a critical topic of research [1]-[14]. Out-of-band interference has been traditionally addressed by increasing the filter order, but the suppression of in-band interfering signals requires more sophisticated preselect RF filtering solutions, particularly for dynamic jamming scenarios. These include the integration of tunable bandstop filters (BSFs) in front of the preselected BPF [2]-[4] or the realization of BPFs with in-band interference suppression capabilities through incorporated BPF/BSF architectures that are codesigned to miniaturize the size of the preselected RF front-end stage [5]-[11].