RF MEMS switches combine extremely low loss and high power-handling in a unique SP4T configuration, which enables the creation of miniaturized and very high performance switched filter banks (SFB).
SFBs are becoming more and more common for both commercial and military applications with the pro- liferation of communications fre- quency bands and the deployment of more frequency-agile radios. Traditional SFBs that use semiconductor devices as the switching element to select discrete filters are increas- ingly preferred over their electromechanical counterparts. In some applications, how- ever, the additional losses associated with semiconductor switches is prohibitive. This is problematic when considering that at least two switches are required, at both the input and output of the filter bank, which can drive losses from switching alone to 3 to 4 dB—or higher depending on the number of filter selections and the frequency range of operation. Such losses can create significant challenges for radio designers, especially in high-power applications where 3 dB cor- responds to a significant amount of power dissipation (i.e., heat) that must be man- aged. Recently, RF MEMS switches have become available that combine extremely low loss and high power-handling capability in a unique SP4T configuration. This enables the creation of miniaturized and high per- formance SFBs. This article explores the un- derlying technology, design approach and resulting performance.