Very High Q-Factor Bandpass Filter Using Additive Manufacturing

A spherical bandpass filter is presented. The main feature of the proposed filter is the use of the spherical mode TE 101 , which presents a higher unloaded Q-factor than the fundamental mode and its proximate higher order modes. As a result, in this work, the mode TE 101 has been exploited in the design of a 2-pole filter with a central frequency at 10 GHz and fractional bandwidth 1.2%. The fabrication has been carried out using the selective laser melting technology in order to exploit the flexibility of additive manufacturing. In particular, two monolithic prototypes have been manufactured. Good agreement between measurements and simulations have been observed, with almost identical results between the two manufactured prototypes, thus proving the repeatability of the process. No tuning screws have been used.