Uwb bandpass filter with upper-stopband improvement using slot-embedded short-circuited stub

A ultra-wideband bandpass filter with good out-of-band rejection 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 form cross-coupled effects. This cross-coupled circuit can effectively reject the harmonic in upper-stopband. The approach provides a low cost solution to improve the upper-stopband without dramatically enlarge the circuit size. Three ultra-wideband filters, 1^st-order, 3^rd-order and 5^th-order ultra-wideband bandpass filter are studied. Finally, 5^th -order is fabricated and measured to verify the predicted results.