Millimeter-wave Bandpass Frequency Selective Structure Using Stacked Dielectric Slabs

A simple stacked dielectric structure is presented to achieve a broadband filtering response at millimeter-wave (mm-wave) frequencies. The structure consists of alternative slabs of different dielectric materials (non-periodic designs possible) to exhibit a bandpass response. The structure is designed using a transmission line model and confirmed with full-wave simulations. Compared to standard printed circuit board (PCB) fabrication, stacked dielectric structures are expected to exhibit better loss performance, due to absence of metallic patterns, and be easier to fabricate at mm-waves because of the absence of constraints from PCB line-width/gap dimension tolerances. An example structure was designed, fabricated, and measured with a center frequency 57 GHz consisting of three dielectric slabs and two air gaps. ANSYS FEM-HFSS simulations of this structure show well-matched bandpass performance, insertion loss of less than 1 dB, and a 3-dB bandwidth of 4.5 GHz. Measurement of the fabricated structure shows excellent performance and correlation with simulation.