Compact bandpass filter with two transmission zeros using dual-mode microstrip resonator and tapped-line geometry

In this paper, a dual-mode lambda_g/2 bandpass filter with two transmission zeros is designed and implemented. Also, the J-inverter is investigated as a function of the impedance and the electrical length of the open-stub of dual-mode lambda_g/2 resonator, and the inverter is alternated by the coupling structure and tapped-line geometry for high out-of-band performance. The second transmission zero of the dual-modelambda_g/2 bandpass filter is defined by the open-stub of the tapped-line geometry as a function of J-inverter. The bandpass filter on the RT-duroid substrate has two transmission zeros of 2.38 and 2.88 GHz and has the insertion and return losses of 1.9 dB and 18 dB, respectively, at the center frequency of 2.48 GHz.