A novel finite-ground coplanar waveguide structure filters with spurious passband suppression

The spurious passband caused by finite-ground coplanar waveguide (FGCPW) coupling structure is analyzed. Semicircular flaw ground structure can shift the spurious passband toward low frequency without affecting passband. Appling of this coupling structure, the FGCPW asymmetric half-wavelength coupling passband filter is designed. It has the center frequency 2.4 5 GHz, the insertion loss 0.3 dB and the bandwidth 0.1 GHz while there is a spurious passband at 1.9 GHz. After utilizing semicircular flaw ground structure, spurious passband is shifted downwards to 1.5 GHz without degrading passband performance. Moreover, this kind of filter can be used for high-frequency.