Finite Ground CB-CPW Bandpass Filter using Vertically Installed Coupled Open-ended Stubs

Abstract

In this paper, a conductor backed coplanar waveguide (CB-CPW) 3rd order bandpass filter is designed using coupled open-ended stub resonator placed vertically to the signal line. Vertically loaded open ended stubs are designed at quarter wavelength so as to behave like a short circuit at the input terminal thus giving a band-accepted response with lesser metallic area or minimum size. Four such coupled open ended resonators are placed in series and also in closely manner to provide greater field confinement of the proposed bandpass filter. The bandpass filter is designed for a center frequency of 2.5 GHz with FBW of 97.89%, insertion loss of <0.5dB, rising and falling edge selectivity of 30.75 dB/GHz and 27.01dB/GHz respectively with a wide stopband of around 4GHz after the desired passband. Further to validate the design technique six such resonators are placed to obtain 5th order bandpass filter.