AlN MEMS filters with extremely high bandwidth widening capability

This paper presents radio frequency (RF) microelectromechanical system (MEMS) filters with extremely high bandwidth widening capability. The proposed filtering topologies include hybrid configurations consisting of piezoelectric MEMS resonators and surface-mounted lumped elements. The MEMS resonators set the center frequency and provide electromechanical coupling to construct the filters, while the lumped-element-based matching networks help widen the bandwidth (BW) and enhance the out-of-band rejection. Aluminum nitride (AlN) S0 Lamb wave resonators are then applied to the proposed filtering topologies. AlN S0 first- and second-order wideband filters are studied and have shown prominent performance. Finally, the AlN S0 first-order wideband filter is experimentally implemented and characterized. The demonstrated first-order filter shows a large fractional bandwidth (FBW) of 5.6% (achieved with a resonator coupling of 0.94%) and a low insertion loss (IL) of 1.84 dB. The extracted bandwidth widening factor (BWF) is 6, which is approximately 12 times higher than those of the current ladder or lattice filtering topologies. This impressive bandwidth widening capability holds great potential for satisfying the stringent BW requirements of bands n77, n78, and n79 of 5G new radio (NR) and will overcome an outstanding technology hurdle in placing 5G NR into the marketplace. Communication: high-performance radio frequency MEMS filters Researchers in China have developed a new type of radio frequency filter with extremely bandwidth widening capabilities, which will be useful for 5G networks. The approach is a hybrid configuration combining a microelectromechanical system (MEMS) filters combined with lumped elements. Dr. Tao Wu’s team at ShanghaiTech University began by modeling MEMS filters based on aluminum nitride resonators. They found that the first-order filter of proposed topology was several times better than existing systems at bandwidth, and that second-order filters improved rejection even further. Next, they fabricated a filter based on this design and characterized it. The bandwidth was approximately 12 times better than conventional standalone resonators. These designs will be valuable to filter out unwanted signals in 5G communications technologies.