Two-poles compact microstrip bandpass filter with sharp transition bands using high permittivity substrate

This article describes the two-pole microstrip band-pass filters using miniaturized center-stubbed open stubs and tapped-line input/output ports. The two-poles bandpass filters by using FR4 and high-permittivity ceramic substrates (with respective dielectric constants of 4.5 and 31.55) are investigated. Microwave dielectric ceramics with high permittivity are commonly applied in several microwave communication components. The advantage of using high permittivity ceramic substrates is to reduce the sizes and increase the performance of microstrip bandpass filters. The responses of the filters using FR4 (ε _r = 4.5, tan δ = 0.015) and Nd(Zn _1/2Ti _1/2)O ₃ (ε _r = 31.55, tan δ= 0.00005) ceramic substrates are designed at a center frequency of 2 GHz. The compact size, low-loss, sharp response, and performance of the filter are presented in this article.