DESIGN OF DUAL-BAND BANDPASS FILTERS USING A DUAL FEEDING STRUCTURE AND EMBEDDED UNIFORM IMPEDANCE RESONATORS

In this paper, a simple method and structure to design a dual-band bandpass filter (BPF) by using a dual feeding structure and embedded uniform impedance resonator (UIR) is presented. In this structure, two passbands can be designed individually and several transmission zeros can be created to improve the band selectivity and stopband performance. The first passband is determined by the dual feeding structure and the second passband is determined by the UIR. Moreover, by using the inter coupling in the UIR, the performance of the second passband can be easily tuned without degrading the first passband. In order to verify the design concept, two filter examples, including 0.9/1.575 GHz for multi-services communication and 2.4/5.7 GHz for wireless local area network (WLAN), are designed in this study. Experimental results of the fabricated samples show a good agreement with the simulated results.