Application of SAW devices to matching elements in RF circuits

摘要

This paper discusses the application of SAW devices to impedance matching elements in RF circuits. First, the application of L-type cell consisting of two SAW resonators is discussed. It is shown that the properly designed L-type cell enables perfect impedance matching with capacitive loads. However, passband width and/or insertion loss become a trade-off with the impedance matching. The result suggests that this matching function could be installed in ladder-type SAW filters consisting of the cascade-connected L-type cells. Secondly, the application of double-mode SAW (DMS) filters is discussed. The DMS filters also exhibit the impedance matching function although their performance is more sensitive to capacitive loads than that of the L-type cell.