AbstractBy using high‐permittivity dielectrics, bandpass filters can be miniaturized. A hairpin‐line filter based on high‐permittivity dielectrics is proposed in this study. Ba2Ti9O20, with high dielectric constant, low loss, and stable temperature is available for the dielectric resonator and is adopted as a material in the fabrication of high‐permittivity ceramic substrates. A tape‐casting technique is employed to produce thin and flat Ba2Ti9O20‐based ceramic substrates. The center frequency of the fabricated bandpass filter is 5.75 GHz and the bandwidth is 742 MHz. The measured insertion and return losses of the filter are −1.34 and −12 dB, respectively. The measured response of the fabricated filter is in agreement with the simulated results. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 164–166, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20408