In the past decade, the wireless industry has undergone a metamorphosis. The industry has turned from a predominantly military-driven market to a cost-conscious, consumer-driven commercial market. At the same time, wireless applications are moving up in the frequency spectrum. A typical example would be the PCS system. The PCS systems are currently designed for the 1.9 GHz spectrum, but the newer designs for wireless communications are moving up to 5.8 GHz.
As the commercial applications move up in the frequency spectrum, there is a renewed interest in high-performance, high-frequency, low-cost substrates.