Miniaturized loop-filter with high out-of-band rejection for future UMTS mobile terminals

This paper deals about the implementation of miniaturized band-pass filters operating on a very narrow bandwidth. An original synthesis technique is proposed for achieving high out-of-band rejection by means of a loop resonator where transmission zeros are introduced through mutual coupling effects. Quite good performances are obtained regarding losses, size and spurious resonances for the proposed topology, which can be considered as a good solution for mobile equipments.