Performance Enhancement of Miniaturized Dual-Band Bandpass Filter

Abstract

Abstract Recently a significant design technique was proposed to develop miniaturized dual-band bandpass filters using multilayered dual-mode resonator. The attitudes of these filters show good performance with 3 GHz upper rejection band. In order to improve the stopband performance of these filters, this article presents a new generation of miniaturized dual-band bandpass filters having extra transmission zero in the upper stopband. The desired transmission zero is generated by electrical physical length (lTZ) equal to a quarter-wavelength open-circuited stub resonator created from the filter structure itself. This is achieved by slipping down the input/output feeding ports from the far end connection points to the desired electrical length. To verify the proposed idea, a dual-band BPF operating at 1.9 GHz GSM and 3.5 GHz WiMax systems is designed, simulated and fabricated. The measured and simulated filter responses are in well agreed. It is observed that this filter has attenuation better than 15 dB over 5 GHz rejection band. The filter circuit area is very small of about 37mm2 terminating the feeding ports.