Design of resonator based ultra wideband bandpass filter in Low Temperature Cofired Ceramic Technology

An ultra wideband bandpass filter is designed by vertically stacking microstrip square ring resonators. The filter is designed to be fabricated in Low Temperature Cofired Ceramic (LTCC) Technology. A wide bandwidth of 3.9 GHz-9.7 GHz has been obtained, which corresponds to a fractional bandwidth of 85%. The insertion loss at the center frequency of 6.8 GHz is observed to be -0.4 dB. The input and output are designed to be measured through 50 ohm Coplanar Waveguide (CPW) lines. A sensitivity study has been presented to show that the design is robust with respect to small changes in critical dimensional parameters, making the design attractive for implementation in LTCC as this process will introduce small dimensional changes unintentionally.