Direct Metal Printed 4th Order Stepped Impedance Filter in the C/X Band

In recent years, additive manufacturing (AM) techniques were increasingly applied to develop RF and microwave components. The main advantage of AM is a reduction in both mass and production time. The AM technique investigated in this paper is direct metal printing (DMP). As a consequence, challenging geometries can be implemented. Here we present a 4th order cavity filter, realized by cascading four lollypop-shaped resonators. The filter was designed to be manufactured in one block using stainless steel as a base material, however, for reasons of workpiece accessibility the two halves and the closing plates of the first prototype were produced separately and subsequently fixed together. Tuning screws were used to adjust the performance. The prototype filter exhibits a measured insertion loss of 1.14 dB with the matching being better than -12.77 dB, a fractional bandwidth of about 3.6% at 7.926 GHz, and a Q-factor of 1600.