Novel Synthesis Method for Wideband Filter with Additional Insertion Phase

In this article, a novel synthesis method for wideband bandpass filters (BPFs) with integrated arbitrary phase shift (PS) is proposed. This design introduces non-resonating nodes (NRNs) at the input and output ports, forming a new wideband BPF configuration. An admittance matrix is constructed to describe the filter, where the desired PS is controlled through termination-related couplings and the self-couplings of the first and last resonators. Moreover, to implement the BPF with lumped elements, an ABCD matrix-based circuit transformation is introduced, which eliminates the need for input/output J-inverters, thereby overcoming their bandwidth limitations in wideband BPFs. To validate the proposed design method, a wideband BPF circuit with a PS range of 120° is designed, fabricated, and measured. The circuit exhibits a passband from 1 to 2.2 GHz, corresponding to a fractional bandwidth of 80.9%. The measured results align closely with simulated data, demonstrating the effectiveness of the proposed method in achieving the desired PS performances.