Tuned to Resonance: Transfer-Function-Adaptive Filters in Evanescent-Mode Cavity-Resonator Technology

A number of promising technologies can be found today in the marketplace of reconfigurable filter ideas. They range from sub-mm-scale acoustic filters, lumped elements, two-dimensional resonators, and full three-dimensional solutions. From a system perspective, an equally diverse pool of communication, radar, electronic warfare, and sensing systems need reconfigurable filters. Despite a strong demand for such filters though, it is not easy to identify a technology that satisfies all requirements. While it is relatively straightforward to satisfy one or two important specifications such as low loss or high selectivity, it is often quite challenging to simultaneously satisfy all of them. For instance, this is particularly true when low power consumption, small form factor, and low loss become simultaneously critical decision factors. Several combinations of such factors can result in necessary design tradeoffs with no obvious solutions. Table 1 summarizes several common deciding factors in selecting a reconfigurable filter technology.