Analysis of microstrip bandstop filter characteristic based on defected microstrip structure

Defected microstrip structure (DMS) has similar characteristics to DGS, such as slow-wave characteristic and rejecting microwaves in certain frequencies, which has been applied in microstrip bandstop filter design to obtain good stopband property and decrease the size of the microstrip filter. This paper proposed a method to realize bandstop filter based on M-shaped defected microstrip structure (DMS), new bandstop filter with four notched bands are proposed. This paper analysis the equivalent lumped circuit of M-shaped DMS, and further analysis resonant frequencies and the insertion loss changes with the parameters of M-shaped DMS. The main advantages of the proposed dual-band bandstop filter can be adjusted to required frequency band by changing the parameters of M-shaped DMS. The design parameters of the filter is optimized by 3D EM commercial software HFSS 13.0, and the simulation results indicated the proposed filter can generate four notch bands at 2.4 GHz, 5.2 GHz, 6.9 GHz and 10 GHz with the insertion loss less than -18dB. The new DMS bandstop filters based on M-shaped DMS has advantages of good performances of miniature size and simple topology. The proposed bandstop filters with four notched bands based on M-shaped DMS can efficiently filter out interfering signals in WLAN band, C band and X band with application prospects.