The last quarter-century has seen extraordinary growth in commercial wireless technology. In the late 20th century, advances were confined primarily to wireless telephony. In the last 15 years, however, there has been an explosion of applications, including GPS, wireless data transfer and currently, the Internet of Things.
Cellular handsets have become more sophisticated, embracing more functionality in very small spaces. Enabling this wireless communication revolution are parallel developments in wireless infrastructure. Ceramic materials have long been used for cellular base stations and other wireless infrastructure applications. Microwave dielectric ceramics were essential components in auto-tuned combiners for 2G (and earlier) systems. They are still used as filters for modern 4G- and LTE-based systems, where the trend is to carrier aggregation, requiring more filters for multiplexing.