A novel compact microstrip bandpass filter with two transmission zeros

A novel compact microstrip bandpass filter composed of two quarter-wavelength (λ4 ) resonators is proposed. By introducing an additional capacitive coupling between two λ4 resonators, two transmission zeros at upper and lower stopbands may be suitably created. The proposed filter has good rejection at twice the center frequency with a very small circuit area. Specifically, a compact microstrip bandpass filter centered at 2.4 GHz is implemented with an area of approximately λ8 x λ4.