Compact dual‐band bandpass filter with high‐passband isolation using coupled lines and open stub

This article presents the design and analysis of a compact dual‐band bandpass filter employing coupled lines and open circuit stub. The filter frequency response contains two passbands with good isolation between them and five transmission zeros in the stopband. The analytical design equations for transmission zero frequencies are obtained based on lossless transmission line theory and the even and odd mode analysis method. A dual‐band bandpass filter operating at GSM (0.9 GHz) and Wi‐Fi (2.4 GHz) frequencies is designed, fabricated, and tested. The proposed design method is verified by the excellent agreement between the simulated and measured results.