Design and implementation of ultra-wideband bandpass filter with non-equiripple responses

In this paper, a novel type of frequency responses of ultra-wideband (UWB) bandpass filter is presented. Different from the traditional Chebyshev transfer function filters, the inband reflection lobes can be theoretically controlled and realized to be a dome-shaped envelope filtering responses. The amplitude of reflection coefficients near the band edge can be easily assigned to be lower than those near the center operating frequency, which is very important for reducing the sensitivity of manufacture errors and thus promotes the industrial mass production. The filter using simple cascaded topology with shunt short-circuited stubs is designed based on the modified design procedure. Because of the existing of the discontinuities of T-junction, the practical design issues have also addressed accordingly. Finally, a prototype of our proposed UWB bandpass filter is designed and demonstrated. This is the first time that a UWB filter with non-equiripple responses is implemented successfully and verified experimentally.