Embedded compact BaTiO3-polymer film VHF band-pass filter

Band-pass filters with low insertion loss and high frequency selectivity are widely used in the modern electric device and communication systems. With the requirement of the electrical system miniaturization, embedded filter was proposed because of its light weight and excellent performance. In this paper, a fully embedded VHF band-pass filter with bandwidth from 280 MHz to 400 MHz is designed and fabricated based on the BaTiO₃-epoxy composite film. The filter is composed of a power plane with cross coupled microstrips and a double helical ground structure (DGS). The size of the band-pass filter is 5mm× 5 mm. It was embedded in a multi-layered FR-4 packaging substrate through the PCB manufacturing process. The measured results of insertion loss and return loss are similar to the simulated results. The measured results shows that the insertion loss is no more than 3.8 dB in pass-band and over 10 dB suppression is obtained at above 1.2 GHz, which is important for the practical application in communication. The embedded band-pass filter using BaTiO₃-polymer film as a substrate is a new way for electronic system miniaturization.