Microstrip dual-band bandpass filter with E-shaped multimode resonator

A microstrip dual-band bandpass filter (BPF) using two E-shaped multimode resonators (MMRs) is presented. Each MMR can not only generate one passband, but also independently control the bandwidth. By utilising the odd-mode and even-mode resonance properties of the proposed MMR, a simple design procedure is described. Besides, two transmission zeros are created owing to the intrinsic characteristic of the proposed resonator. To validate the design theory, a dual-band BPF for GSM and WLAN applications was designed, analysed and fabricated. Measurements have good agreement with simulations.