A Novel Sub-Millimeter-Wave UWB Filter

A novel sub-millimeter-wave bandpass filter used in ultra-wideband (UWB) systems is developed in this paper. The filter consists of two microstrip square ring resonators loaded with two lambda
₀
/4 and 3lambda
₀
/4 open stubs, respectively, where lambda
₀
is the guided-wavelength at the midband frequency of the filter. The filter has a midband frequency of 25.5 GHz and a 3-dB bandwidth of 5 GHz (20%). Theoretical and measured results show that the filter is low loss within the passband, has sharp attenuations near the passband, and exhibits very wide stopband due to the introduced multiple transmission zeros.