3D manufacturing using laser direct structuring and the application on the development of antenna systems

Abstract

The development of radio systems is subject to constantly increasing demands. These concern the function to be implemented as well as the geometric dimensions of the RF devices in decreasing installation spaces. One resulting aspect is that the antenna can no longer be developed as a single component and be integrated subsequently. It is rather necessary to consider the installation space as a part of the antenna and to use it electromagnetically according to the requirements. One manufacturing technology that inherently takes up this approach is Moulded Interconnect Devices (MID) technology. MIDs are three-dimensional plastic parts which are selectively metallised. The electronic/electromagnetic functionalisation of mechanical components, such as housing parts, is thus possible. The manufacturing and material parameters of the different MID manufacturing processes are often characterised regarding the mechanical or electrical requirements, although e.g. the MID LDS (Laser Direct Structuring) process has been used for years for the production of antennas in consumer devices. Therefore, the main aim of the present work is to carry out a structured technological analysis of the LDS process for high-frequency applications up to 70 GHz and to verify the results by means of antenna developments, which use the three-dimensional design scope provided by the technology. After a description of the manufacturing process of the LDS process, the relevant parameters with regard to radio frequency systems are derived. Based thereon, a detailed discussion of the mechanical parameters, the dielectric material parameters of the LDS plastics as well as the applied metallisation is carried out. The results are verified by measurements. These findings are subsequently used in the development of various antenna concepts which can be fabricated using the LDS process. First of all, two antenna systems are developed to be integrated into a vehicle. The first system takes up a current installation space, a roof antenna module, while a second system is aimed at a new installation space. The developed antennas are realised with the LDS method and subsequently characterised. In addition, two antenna concepts are examined which are independent of a specific installation space, but which take into account the possibility of adapting them to the installation space as an optimisation goal. One concept covers the use of 3D manufacturing in connection with microstrip antennas. A prototype of an active patch antenna for Global Positioning Satellite System (GPS) which combines circuit and antenna on a three-dimensional substrate is realised. The second approach includes antennas which are fed by dielectric filled waveguides. Two prototypes in the 24 GHz and 61 GHz ISM band verify the suitability of the manufacturing technology for frequencies in the millimetre wavelength range. Finally, the antenna concept is investigated on the basis of electromagnetic field simulations in a generic installation space.