Multiple Band and Multiple Frequency Dielectric Resonators Tunable Filters for Base Stations

The new tunable filter technology with truncated cone resonators is used here to realize multiple bands in different center frequencies in the same housing and with the same resonators. The bandwidth is varied from 20 MHz to 5 MHz and the center frequency is varied from 1930 MHz to 1990 MHz. The filter responses for 20 MHz and 5 MHz are achieved through complete external tuning and no cross couplings are applied. For the 15 MHz and 10 MHz responses the cross couplings are applied. The dielectric constant for the truncated cones and dielectric plugs is epsivr=35 and provides a very high Quality Factor Q and very good intrinsic spurious, which are so crucial for such a flexible design. To our knowledge this tunability in both bandwidth and frequency without affecting the Q is achieved for the first time. The design is patent-pending and we strongly believe that this represents a very important step towards the goal of remotely controlled filters for base stations.