Design and implementation of UWB bandpass filter with a frequency notch for choking back the interference from narrow band wireless communication systems

In this paper, an Ultra-Wide Band (UWB) bandpass filter with a frequency notch is designed and implemented. The filter is realized by combining the highpass characteristic of Substrate Integrated Waveguide (SIW) with the lowpass characteristic of a step-impedance filter. Open stubs are embedded in the microstrip-to-SIW transitions to generate the frequency notch. The bandwidth of the UWB bandpass filter is from 3.1 GHz to 10.6 GHz, and the measured insertion loss in the passband is less than 1 dB (including the insertion loss of two connectors). A sharp notch at 5.8 GHz is achieved in both simulation and experiment. The tested depth of the frequency notch is about -31 dB. The notch is deep enough to choke back the interference from 5.8 GHz narrow band wireless communication systems.