Print parallel coupling wideband filters on Al2O3 ceramic substrate

Abstract

In this paper, low loss wideband 3 order parallel-coupled microstrip line filters are fabricated, and the influences of the designed parameters are well developed in this study. As the displacement parameter A increases, the insertion loss and ripple decrease and the bandwidth increases; As the displacement parameter B increases, the bandwidth decreases and the insertion loss and ripple increase. On the other word, for the purpose of low ripple and wideband, the best choice is to increase A and decrease B. For the interval parameters C and D, increasing of them will decrease bandwidth, for the reason of wideband, decrease the interval parameters (C and D) will be a good choice, however, the decrease of interval will also increase the coupling of each resonators. Due to the higher the dielectric constant and the high quality factor of the Al2O3 ceramic substrate, the wideband filters have the advantages of small size (about 25 mm x 6.2 mm), good insertion loss and the ripple characteristics in the passband, wide bandwidth and large left-transmission zero. From above results, the fabricated filters are suitable for the wideband microwave applications of WLAN system.