Advanced Synthesis of Wide-Tuning-Range Frequency-Adaptive Bandpass Filter With Constant Absolute Bandwidth

This article proposes an advanced synthesis of the frequency-adaptive bandpass filter (FA-BPF) with constant absolute bandwidth (ABW). The proposed synthesis is based on the element-variable coupling matrix (EVCM), which is directly extracted from the classical filter polynomials. The extraction method is presented, investigated in detail, and confirmed by a set of numerical simulations. All frequency-dependent couplings between the resonators...