Low-loss RF filter through a combination of additive manufacturing and thin-film process

Combination of thin-film process and 3D printing is utilized to demonstrate a low-loss maximally flat five element stepped impedance low-pass filter with a cutoff frequency of 3 GHz. The filter is patterned on a thin LCP substrate with no ground plane and it is mounted on a metal coated 3D printed plastic cavity using a Lego-like process. This leads to the formation of a filter on a thin membrane suspended in air above the ground plane. Simulations were carried out using a commercial FEM simulation tool and measurements are carried out over a frequency range of 0.1-8 GHz. Simulation and measured results match very closely. This paper demonstrates that a combination of 3D printing and thin-film processes allows the fabrication of novel RF structure that would be difficult to realize using conventional approaches.