An adaptive computer-aided design-and-tuning scheme for a predistorted filter with uneven-Q effect

The predistorted filter, which can achieve a high equivalent Q-factor, begins to be adopted on the input multiplexer (IMUX) of a satellite payload system. This type of filter is built by low and likely uneven Q resonators. The design and tuning of such a predistorted filter is much more complicated than an ordinary high Q filter because the actual unloaded Q for each resonator will be only available at the tuning stage. Up to now, most designs are based on an equal Q assumption and very few published works have addressed the tuning procedure of such filters. In this paper, an adaptive design-and-tuning scheme for a predis-torted filter is given. An 8-pole predistorted dual-mode dielectric resonator filter is designed and tuned for demonstration purpose. This design-and-tuning scheme takes the stray couplings and the uneven Q factors into account. The finally realized filter achieves an equivalent Q of higher than 10,000 while the actual unloaded Q for each resonator ranges from 1,100 to 2,900.