Bandpass filters are widely deployed in modern RF communication systems. The mathematical concepts of these filters, their characteristic functions, and coupling matrices were discussed by many authors. However, when realizing an actual 3-D fillter structure, little information is available in literature. This thesis presents a step-by-step guide for the design of a resonant cavity based filter. It starts from a coupling matrix, continues with the simulation of 3-D models and works its way up to manufacturing the filter. The design is optimized for in-house production, considering limits of the available machines and materials. Therefore, the designed filter is not optimal from its electrical characteristics, however critical parameters can be determined. Additionally, two common techniques for loss reduction, i.e. polishing and silver-plating, are experimentally evaluated. To do so, a simple resonant cavity is designed. To determine the inuence on the losses, the unloaded quality factor was estimated. Therefore, two common quality estimation methods were applied on the cavity, utilizing di_erent energy coupling mechanisms. However, these did not show the desired accuracy. Consequently, a new method is developed, which considers coupling mechanism imperfections. Polishing was found to give a negligible loss reduction, while silver-plating indicates a quality factor improvement of 33%. Hence, silver-plating was also applied to the filter in order to reduce the losses. With this technique, a filter was designed with a very low insertion loss, which fits the requirements of the design. Furthermore, this was achieved with minimized manufacturing effort, allowing to build it with simple machines.