Non-Foster Elements Pave the Way to Design Novel Wideband and Tunable Bandpass Filters

Non-Foster elements (NFEs) offer some important advantages for the design of wideband and tunable microwave bandpass filters (BPFs). A possibility to design a stable 30%-wide three-pole BPFs with two NFE-based impedance inverters is demonstrated for the first time. Moreover, such a filter is shown possible to exhibit a higher tuning range of the center frequency compared to the BPF with conventional impedance inverters.