Advanced RF filters for wireless communications
Kai Yang, Chenggong He, Jiming Fang, Xinhui Cui, Haiding Sun, Yansong Yang, Chengjie Zuo
Abstract
This paper provides a comprehensive review of advanced radio frequency (RF) filter technologies available in miniature chip or integrated circuit (IC) form for wireless communication applications. The RF filter technologies are organized according to the timeline of their introduction, in conjunction with each generation of wireless (cellular) communication standards (1G to 5G). This approach enables a clear explanation of the corresponding invention history, working principles, typical applications and future development trends. The article covers commercially successful acoustic filter technologies, including the widely used Surface Acoustic Wave (SAW) and Bulk Acoustic Wave (BAW) filters, as well as electromagnetic filter technologies based on Low-Temperature Co-fired Ceramic (LTCC) and Integrated Passive Device (IPD) filters. Additionally, emerging filter technologies such as IHP-SAW, suspended thin-film lithium niobate (LiNbO3 or LN) resonant devices and Hybrid are discussed. In order to achieve higher performance, smaller form factor and lower cost for the wireless communication industry, we believe that fundamental breakthroughs in materials and fabrication techniques are necessary for the future development of RF filters.