Coupled-line sharp notch filter with significant improvement of attenuation

Novel microstrip notch filters using dual-mode patch resonators are investigated. It is shown that highly selective band reject filters can be realized with simple circuit topologies. The proposed notch filter consists of a microstrip dual-mode resonator with a coupled microstrip line. A theoretical investigation has confirmed that this configuration is capable of providing sharp notch filtering. Furthermore, the feasibility of this filter is verified experimentally.