Fraunhofer Institute for Ceramic Technologies and Systems IKTSMillimeter waves (mmW) offer unique properties because they behave quasi optical from a frequency range above 100 GHz. This characteristic makes it possible to produce radars with unprecedented accuracy and communication systems (6G and beyond) with ultra-high bandwidth.
Packagings for such high frequencies systems up to operations of 1 THz are usually realized with metallic split-blocks, which are complicated to machine and therefore expensive in production. Advantages of this technology are their flexibility and unrivaled low attenuation. Unfortunately, the resulting costs and the size of waveguides are prohibitive for commercial success of such systems. Especially high frequency applications of above 200 GHz will provide prospective opportunities, because the natural attenuation of the atmosphere offers a unique and wideband window in this frequency range. With the help of this high bandwidth, cost-effective, high-resolution radar sensors or ultra-high bitrate communication lines could be realized.
Together with Fraunhofer Institute for Applied Solid State Physics IAF, Freiburg, the basis for a new cost efficient mmW - packaging technology should be developed in a collaborative project. The described problems in the frequency range of 100 to 300 GHz could be solved by the usage of Low Temperature Co-fired Ceramics (LTCC) in combination with high-resolution Aerosol Jet printed transmission lines. An extensive benchmarking was realized for the available RF LTCC materials. First S-parameter measurements are showing very promising results for printed GCPWs (GCPW = Grounded Coplanar Waveguide) for the LTCC material Ferro A6M (Fig.1, left and Fig. 2). Additionally laser structuring of GCPWs of printed thickfilm surfaces on LTCC were successfully tested (Fig. 1, right and Fig. 3, right). The S12-measurement in H-Band shows losses of the printed microstrip line less than 0.7 dB/mm for 240 GHz. The reflection coefficient S11 stays below - 15 dB for up to 250 GHz. A steady effective dielectric constant εr, eff of about 4.0 and tangent δ of 0.0062 for Ferro A6M LTCC material could be determined at 200-330 GHz. With the help of the described technology, complete RF frontends could be hermetically packaged until 300 GHz within a LTCC packages for commercial purposes.
Actually a low loss interconnection technique is investigated to reduce the losses between the printed waveguides on the substrates to the connections of the MMICs (Monolithic Microwave Integrated Circuit) directly with printing technologies to substitute or lossy wire bond or flip chip interconnections (see Fig. 3, right). Additionally wide-band antennas on LTCC for D- and H-Band applications are studied.