Tunable dual‐band bandpass filter for WLAN applications

This article proposes the design of tunable dual‐band filters for multiband multistandard systems, specifically for wireless local‐area network applications. The two main goals are to provide frequency tunability in the second band while maintaining the first band fixed and to obtain a structure capable of offering a ratio between the second and first passband center frequencies larger than 2. To this end, a capacitively loaded stepped‐impedance resonator is proposed for integration in dual‐band filters. A detailed analysis of the resonator is provided. A filter has been designed to validate the concept. It demonstrates operability in wireless local‐area network frequency bands, with a fixed first band at 2.45 GHz and a second band which can be tuned between 5.75 GHz and 5.25 GHz.