A dielectric-filled dual-band bandpass filter based on SISL technology

This paper proposes a dielectric-filled dual-band bandpass filter (DF-DBBPF) using substrate integrated suspended line (SISL) technology to realize the miniaturization of the filter. In this design, high dielectric constant material is embedded in the SISL air cavity to construct a high equivalent dielectric constant and miniaturize the circuits. The high dielectric constant material is fixed directly by the SISL cavity. Meanwhile, by using T-junctions to design the dual-band bandpass filter, each passband response can be designed independently. With the help of the EM simulation software, all the dimensions are determined and the DF-DBBPF is processed and tested. The simulated and measured results of this design have the same tendency. The return loss of the two passbands are both better than 15 dB and the size of core circuit is only 0.058λ_g×0.139λ_g, which λ_g represents the guided wavelength at the central frequency of the first passband. The DF-DBBPF is with the advantage of compact size and self-packaging. Meanwhile, low-cost FR4 is chosen for all seven substrate boards.