Predistorted Ku-band rectangular waveguide input filter

Abstract

In current Ku-band satellite telecommunication sys- tems usually a working band selection is performed by means of an input filter before the LNA. Moreover, in some architectures more stringent selectivity requirements may be needed in order to reject cross-coupled transmission power signals coming into the reception chain, being necessary an spurious reject filter after the LNA. On the other hand, depending on the near rejection requirements implementing transmission zeros in the filter response maybe needed. However, this also deteriorates in- band response, affecting channels in the extremes of the reception band. In-band response can be improved again by increasing input filter quality factor using predistortion synthesis technique, but at the cost of higher insertion loss and worse reflection response. This work analyses how predistortion technique can be applied to the design of Ku-band rectangular waveguide filters with transmission zeros implemented through cross-couplings in order to improve in-band performances. Moreover, undesired effects arising from applying this technique are also discussed. From authors knowledge, it is the first time this synthesis technique is applied to rectangular waveguide filters with cross- couplings.