The research of cascaded band-pass filter with high performance based on LTCC

It is very important for filter's performance to improve the stop-band rejection. To achieve high performance, cross coupling to add transmission zeros and technology of cascaded filter are considered. This filter is created by using LTCC technology. Using the circuit simulation and 3D simulation software to optimize and simulate, the measured results of the filter match well with the electromagnetic simulation, the center frequency is 140 MHz, its bandwidth is 20 MHz, between 0 MHz and 115 MHz the stop-band attenuation is better than 40 dB and the same as the frequency between 200 MHz and 300 MHz. Due to the low frequency and long wavelength of the filter, it belongs to the VHF, it is realized by semi-lumped and semi-distributed structure used in the design to make it smaller. Its size of the fabricated filter is only 9 mm×3.2 mm×1.5 mm.