Tunable Triple-Notched Ultra-Wideband Bandpass Filter for Efficient In-Band and Out-of-Band Interference Mitigation

This study analyzes the growing need for effective in-band and out-of-band interference mitigation in ultra-wideband (UWB) communication systems. We present a novel microstrip bandpass filter (BPF) with changeable triple-notched bands that preserves a large passband and a higher stopband. The filter comprises a multimode resonator (MMR) architecture that incorporates a hollow T-shaped structure that generates two transmission zeros at the passband boundaries, thereby boosting selectivity. Furthermore, we deploy a circular complementary split-ring resonator (CCSRR)-based metamaterial to extend the upper stopband and implement a folded 王-shaped electromagnetic bandgap (EBG) architecture for dynamic notch frequency modulation. This design achieves sharp notches at 4.93 GHz, 6.32 GHz, and 9.81 GHz, efficiently minimizing the interference from WLAN and X-band satellite signals. The simulation results revealed a passband ranging from 3.06 to 10.79 GHz, with an insertion loss of less than 1.2 dB and a relative bandwidth of 112.85%. The filter exhibits significant selectivity, including a skirt factor of 0.91 and an upper stopband reaching 19.8 GHz with an insertion loss of 18 dB, rendering it suitable for UWB applications that require substantial interference rejection.