Novel Miniaturization Method for Wideband Filter Design With Enhanced Upper Stopband

In this paper, a novel miniaturization method for filter implementation is presented and validated. According to frequency response transformation, the filter structure has the wideband bandpass response in the required frequency band which is lower than the operation frequency. The in-band and out-of-band characteristics are also improved to realize wide passband and stopband responses. For demonstration, three filters are designed based on the proposed ideas. The efficient circuit area is reduced by 56.8%-64.7% compared with the conventional wideband filter, indicating significant miniaturization using the proposed method. Another advantage of our work is that the stopband is extended to more than than other wideband filter structures. Good agreement between simulation and experiment is obtained.