Dual-mode resonator with modified dual-square-Loop for WLAN and WiMAX quad-band filter design

Abstract

We propose the improved configurations with dual-mode dual-square-loop resonators DMDSLR for quad-band bandpass filter BPF design. The modified DMDSLR filter employs two sets of the loops. The square loop is designed to operate at the first and third resonated frequencies 2.4/5.22 GHz and the G-shaped loop is employed at the second and fourth resonated frequencies 3.59/6.6 GHz. The resonant frequency equations of DMDSLR are introduced for simply designing quad-band BPF. Resonant frequencies can be controlled by tuning the perimeter ratio of the square loops. A systematic design procedure with the design map is applied for accuracy design. To obtain lower insertion loss, higher out-of-band rejection level and wider bandwidth of quad-band, the miniaturized DMDSLR with meander-line technique is proposed. The proposed filters are successfully simulated and measured showing frequency responses and current distributions. It can be applied to WLAN and WiMAX quad-band systems. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:332-340, 2014.