High-Selectivity Bandpass Filter With Asymmetrical Frequency Response for Wi-Fi 6E Applications

A high-selectivity and compact-size bandpass filter (BPF) has been developed for Wi-Fi 6E applications. By using the cross-coupled technique, a transmission zero (TZ) can be generated on the lower side of the passband and thus forming an asymmetrical frequency response. For verification, a fourth-order BPF was designed and fabricated using microstrip technology. The measured transmission responses agree well with the simulation and synthesis. Compared with other recent works of BPF design, the proposed BPF demonstrates advantageous features in terms of a low insertion loss of 0.7 dB, a compact size of $0.26 \lambda_{g} \times 0.43 \lambda_{g}$, and a sharp roll-off rate (ROR) of 145 dB/GHz.