Design and Experiment of 340-GHz Band Pass Filter With Low Insertion Loss

This paper demonstrates a 340-GHz band pass filter with a low insertion loss of ∼-0.6 dB and a bandwidth of ∼6%. This paper studies the relationship between filter diaphragm thickness and resonator length, and the quantitative relationship between insertion loss and fabrication tolerances. The diaphragm is quantitatively analyzed and the resonators lengths with correction factors are calculated for the accurate and robust filter parameters, and the simulation results based on calculated parameters show a robust filter structure as well as a good agreement with the theoretical analysis. The surface roughness and filter structure sizes deviation with different tolerances are studied and calculated for insertion loss. Finally, a filter with low insertion loss and good robustness is achieved by calculated parameters and a certain fabrication tolerance. Different fabrication precisions are carried out to verify the effect of size tolerances on the filter performance, including insertion loss and structural robustness. The filters, designed by the parameters analysis and fabricated by ≤ ∼ 7.5-μm accuracy show good agreement between the simulation results and the test results, and when fabricated accuracy is ∼5 μm, the insertion loss is ∼-0.6 dB and the return loss is < -20dB.