A UHF-band miniaturized LTCC band-pass filter with high performance

This letter outlines the design and manufacture of a UHF-band miniaturized band-pass filter realized by low-temperature cofired ceramic (LTCC) technology for super heterodyne microwave receiver applications. A distinct feature of this filter is the smaller size than conventional filter at such a low frequency and steady pass-band temperature electrical performance compared with surface acoustic wave filter. The band-pass filter with a central frequency of 750 MHz and a 40 MHz pass-band is designed as a three-dimensional (3-D) structure based on distributed components. This filter has excellent out-of-band attenuation performance and it has 50.1 dB and 56.8 dB of attenuation at 550 MHz and 950 MHz respectively. The measured insertion loss is less than 2.7 dB at 750 MHz, and the input/output VSWR is less than 2.0. The overall size of the miniaturized filter is only 4.5 mm × 3.2 mm × 1.5 mm.