Wideband microstrip ring resonator bandpass filter with embedded rings

In this paper, a novel ring resonator bandpass filter (BPF) is proposed. The proposed filter presents a wide bandwidth and high selectivity and wide stopband. Wide stopband with high attenuation is reaped by utilizing embedded rings. The presented filter exhibits three resonances at the upper stopband. So, by producing three resonances at the stopband a wide stopband filter was designed. The other feature of the proposed filter is that it does not utilize any stepped impedance resonator inside and outside the ring and all stubs are inside the ring which can save filter size. The passband of implemented is from 3 to 7 GHz and the stopband of the proposed filter is from 7 to 13.25 GHz with attenuation of −19 to −50 dB.