Integration of slot antenna with evanescent-mode filter for tunable front-end applications

An evanescent-mode cavity filter integrated with a slot antenna is presented herein. Evanescent-mode cavities are commonly used to design low-loss filters due to their high quality (Q) factors and small size. The integration of the slot antenna and evanescent-mode filter provides nearly-zero transition loss with reduced size. The filter/antenna is designed at the center frequency of 8.56 GHz with a fractional bandwidth of 2.86%. The center frequency of this filter/antenna is then tuned from 8.18 to 8.80 GHz by just changing the resonant frequency of the resonators. The impedance matching, filtering shape, and radiation pattern of the filter/antenna system are preserved across the entire tuning range.