A new class of microwave filters using vertically stacked coupled open loop resonators

The design of microwave bandpass filters with compact circuit size has attracted tremendous research interests worldwide recently since the well-established traditional techniques do not satisfy this requirement. Development of advanced technology in emerging wireless communications such as multifunction ultra-wideband (UWB) systems, personal communication network WLAN, Bluetooth and remote sensing and imaging radars; demand ultra-high integrating density components and techniques. The bandpass filter should also be able to offer a good performance, constant group delay over the desired passband, high selectivity, wide band rejection, low insertion loss, low manufacturing cost and high reliability.