Two dual-band second-order highly selective band pass filters operated at 3.5/5.5 GHz and 3.5/6 GHz for wireless local area network /worldwide interoperability for microwave access WLAN/WiMAX applications are introduced in this paper. The designed filters are inspired of utilizing two coupled open-loop resonators loaded with stub, spiral resonators and lumped capacitors. The filters are designed based on calculating the desired coupling matrix and the external quality factor. The first and the second filters are designed at the fundamental mode of 3.5 GHz then the first filter is loaded with two spiral resonators in the microstrip line to produce the desired band stop behaviour, which in turn achieves the second pass-band. However, the second band of the second filter is achieved by loading the stub with the lumped capacitors, which controls the second mode. The centre frequency of the second band is adjusted by varying the lumped capacitors values. The two designed filters have insertion loss less than 0.7 dB in the pass-band region, high selectivity with more than 4 transmission zeros and more than 20 dB attenuation level in the stop band region. The suggested filter has compact size and high selectivity with tunability behavior. The two filters are fabricated and measured to validate the simulated results.

中文翻译：

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利用0°馈电结构和集总电容器的WLAN / WiMAX应用双频双模带通滤波器的设计

本文介绍了两个工作在3.5 / 5.5 GHz和3.5 / 6 GHz的双频带二阶高选择性带通滤波器，用于无线局域网/微波访问WLAN / WiMAX应用的全球互通性。设计的滤波器的灵感来自于利用两个装有短截线，螺旋谐振器和集总电容器的耦合开环谐振器。基于计算所需的耦合矩阵和外部品质因数来设计滤波器。将第一和第二滤波器设计为3.5 GHz的基本模式，然后在微带线中将两个螺旋谐振器加载到第一滤波器中，以产生所需的带阻行为，进而实现第二通带。但是，第二个滤波器的第二频带是通过将集总电容器加载到短截线中来实现的，它控制第二种模式。通过改变集总电容器值来调节第二频带的中心频率。这两个设计的滤波器在通带区域具有小于0.7 dB的插入损耗，在四个以上的传输零点具有较高的选择性，在阻带区域具有大于20 dB的衰减水平。建议的滤波器具有紧凑的尺寸和具有可调性的高选择性。制作并测量两个滤波器以验证仿真结果。建议的滤波器具有紧凑的尺寸和具有可调性的高选择性。制作并测量两个滤波器以验证仿真结果。建议的滤波器具有紧凑的尺寸和具有可调性的高选择性。制作并测量两个滤波器以验证仿真结果。