A triple-band BPF using cross coupled of tri-section SIRs with capacitive load

摘要

This paper proposes the triple-band band pass filter for applications of GSM, Wi-MAX, and WLAN systems. The filter comprises of step-impedance resonators (SIRs) connected with capacitive load, which are combined by using cross coupling technique. Additionally, tapered lines are used to connect at both ports of the filter in order to enhance matching for the triple-band resonant frequencies. The filter can operate at the resonant frequencies of 1.8 GHz, 3.7 GHz, and 5.5 GHz, respectively. At these resonant frequencies, the measured return losses are 13.67 dB, 18.9 dB, and 17.88 dB, while the insertion losses are 2.55 dB, 2.89 dB, and 2.78 dB, respectively. Moreover, the filter size is compact when compared with the conventional open-loop cross coupling triple-band band pass filters.