Dual UWB bandstop filter based on M-shaped defected microstrip structure

Abstract

As a key component of the RF system, UWB filter with notched bands has gradually become a research hotspot and defected microstrip structure (DMS) with the properties of slow-wave, rejecting microwaves in certain frequencies has been applied in microstrip filter design, which can obtain good stopband property and reduce the size of the microstrip device. This paper proposed a dual UWB bandstop filter based on M-shaped defected microstrip structure, which has realized dual band-notch function with deep and sharp shirt by introducing M-shaped defected microstrip structure design on the basic UWB BPF. The basic UWB BPF is composed of microstrip lines and rectangular patch multiple mode resonator (MMR) with four short-circuited stubs with length of a quarter of wave length, which realized the flat ultra-wideband response from 2.84 GHz to 10.78 GHz and sharp rejection skirt. This paper further analysis of resonant frequencies and the insertion loss changes with the parameters of M-shaped defected microstrip structure. By adjusting the parameters of M-shaped defected microstrip structure the dual notch frequencies can be changed at the desired frequency. The main advantages of the proposed filter is that dual center notch frequencies can be easily tuned to certain frequencies in a wide UWB frequency band, so the low notch frequency can be easily tuned from 4.1GHz to 4.4 GHz and the high notch frequency can be easily tuned from 7.9 GHz to 8.4 GHz with the insertion loss less than −30dB. The design parameters is optimized by 3D EM commercial software HFSS 13.0 and ADS 2013. The simulation results indicated that the proposed UWB bandstop filter can generate two stop bands at 7.9 GHz and 8.4 GHz. By adjusting the parameters of M-shaped defected microstrip structure can change the notch frequency in C band and X band to remove interference with certain application prospects.