Notch-band UWB bandpass filter using slot-embedded short-circuited stub
A notch band ultra-wideband bandpass filter with good out-of-band rejection, controllable and multiple transmission zeros in notch band and good inband performance is presented in this paper. A shunt short-circuited stub is used to build up the initial ultra-wideband skirt. A slot is then embedded into the short-circuited stub to achieve cross-coupled effects. This cross-coupled circuit can effectively reject the harmonic in the upper-stopband. Based on this circuit, the 1st-order, 3rd-order and 5th-order bandpass filter is discussed to study the improvement of the selectivity and harmonic suppression. In addition, a notch-band is implemented by adding an open-circuited stub, which is with via to form a shunt connected LC resonator. By implementing multiple shunt LC resonator, multiple transmission zeros can be achieved in the notch-band. Finally, a notch-band filter prototype is fabricated to experimentally verify the predicted results.