HTS power filters for output multiplexers in satellite communications

The paper reports on advances in the development of high temperature superconducting 40 MHz bandwidth four-pole bandpass filters with elliptic frequency response for 3.4-4.2 GHz (extended C-band) output multiplexers of communication satellites. By employing the concept of "edge-current-free" disk and ring resonators the filters possess a small size but can handle 60 W transmitted power with sufficiently low insertion loss and intermodulation. Measurements of the unloaded Q-factor and power handling as function of the temperature, performed at single disk resonators made from YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// on LaAlO/sub 3/ and sapphire substrates indicate the conditions under which the required Q-factor of about 1.5/spl middot/10/sup 5/ and sufficiently low nonlinear response up to an oscillating power of 15 kW can be obtained. Approaches for shifting the resonant frequencies of unwanted modes relative to the resonant frequency of the employed TM/sub 010/-mode are outlined and shown to be necessary for the envisaged multiplexer applications.