Multilayer Dual-Band Bandpass Filter in Low-Temperature Co-Fired Ceramic Substrate for Ultra-Wideband Applications

In this paper, we propose a new multilayer dual-band bandpass filter in a low-temperature co-fired ceramic (LTCC) substrate for ultra-wideband (UWB) applications. This bandpass filter consists of two wideband bandpass filters and matching circuits. It is for UWB applications, which use the band group 1 (3.168-4.752 GHz) and the band groups 3 and 4 (6.336-9.504 GHz) of multiband orthogonal frequency-division multiplexing systems. The basic characteristics of the bandpass filter are simulated with a circuit simulator and an electromagnetic simulator. We also verify the effectiveness of the presented filter through experiments using LTCC technologies. The measured results of the fabricated filters agree well with the simulated results, and we obtain the good wide-passband characteristics with the desired notch band. The insertion losses are less than 2.5 dB in the wide passbands, which satisfies the target characteristics. Moreover, out-of-band attenuation performances almost satisfy the target characteristics: for instance, the attenuation level is higher than 33 dB from 0.8 to 2.17 GHz, 17 dB from 2.4 to 2.48 GHz, and 26 dB from 5.15 to 5.35 GHz. The fabricated filter has a size of 7.5 x 3.8 x 0.386 mm(3).