Split-Type Dual-Band Bandpass Filters With Symmetric/Asymmetric Response

Split-type dual-band bandpass filters (DB-BPFs) with symmetric/asymmetric response are presented in this letter. Two different responses are achieved by placing transmission zeros inside the different position of the virtual wide passband, which originates from two-pole wideband BPF. Presented with the equivalent circuit of the coupling structure, the analytical formulas of the structure based on the $\lambda $ /4 stepped impedance resonators are derived according to the synthesized coupling matrix. Compared with the conventional capacitive-coupled filters, low insertion loss and relieving the limitations of fabrication process can be obtained. Moreover, the proposed DB-BPFs have low insertion losses, good return losses, high selectivity, and wide stopband.