A research of bandpass filter with miniaturization based on semi-lumped and semi-distributed structure

Due to the low frequency and long wavelength of the filter, it belongs to the VHF. In order to ensure its miniaturization, this filter is realized by semi-lumped and semi-distributed structure. To ensure its high performance, we use the LTCC technology which is advanced in the world. The stopband rejection characteristics have been improved by cross coupling and the technology of filter cascading. Using the circuit simulation and 3D simulation software to optimize and simulate, the measured results of the filter satisfy its performance requirement. The centre frequency of the BPF at 170MHz, its bandwidth is 60 MHz, between 50MHz and 100MHz the stop-band attenuation is more than 20dB and the same result is between 280MHz and 400MHz. The size of fabricated filter is only 9mm × 3.2 mm × 1.5 mm.