Microstrip Bandpass Filter with Apertures in Ground Plane
 
     
 

Geometry & Results

Source

M. Velazquez-Ahumada, et al., ?arallel coupled microstrip filters with ground-plane aperture for spurious band suppression and enhanced coupling,?IEEE Transactions on Microwave Theory and Techniques, vol.52, no.3, pp.1082-1086, March 2004.