Design of Compact Bandpass Filters with λg/4 Short Stubs Using Transmission Zero

In this paper, compact bandpass filters with λ
_g
/4 short stubs by microstrip line on duroid substrate are presented. This kind of filter shows flexible bandwidth with variation of the position of the short stub using the external quality factor, Q
_e
without changing the impedance value at microwave. This filter provides compact design and sharp skirt characteristic by transmission-zero. The bandpass filters can be realized with wide (60 %) and narrow (10 %) bandwidth just by adjusting the position of the short stubs. They show the insertion losses of 0.5 dB and 1.5 dB, and the return losses of 10 dB and 13 dB at the center frequency of 2 GHz, respectively.