To answer the increase demand of connected objects, more communication devices are required, and therefore more antennas. These devices have to be more affordable, smaller, and as energy efficient as possible, especially for low data rate satellite communications, which are a new target of startups and laboratories such as LEAT(Laboratoire d’Electronique, Antennes et Télécommunications), a French laboratory dedicated to Information and Communication Technologies (ICT) .
To reach this goal, LEAT is working on S-Band antennas (frequency from 2 and 4 GHZ) and adapted dielectric resonator (DRA). The laboratory has identified Zetamix technology as a tool to reach their goal : shaping next generation antennas.
Dielectric resonnators : a cutting-edge part
Dielectric resonators have a huge role in such antennas : they broadcast the waves to widen their range. They are made in ceramic, for instance zirconia which shows both good permittivity and a small loss of signal. For each frequency standards, a specific resonator is required, with both a permittivity given by the choice of material and an adapted design. However, reaching the right resonance frequency while maintaining a small size device is no easy task. Indeed, to compensate the value of permittivity of a material, engineers usually have to change the size of the object, which triggers design issues.
Moreover, regular antennas are made in two parts : one for supporting downlink satellite communication and the other for uplink satellite communication. Two dielectric resonators with different resonance frequency are required. Engineers try to find the right material and the right ratio between the size of the part and the permittivity for both parts.
Printing different porosities thanks to ceramic 3D printing
That is where Zetamix technology comes in. In addition to provide technical material such as zirconia, Zetamix 3D printing is a very simple and affordable technology. The process of fabrication is simple: the part printed is a mix of binder and ceramic. To reach a density of 99%, a debinding and sintering post process is required. By combining stunning material properties provided by the brand and the impressive shaping possibilities of 3D printing, the lab succeeded to find a solution for a low investment.
To print their DRA, LEAT used zirconia which shows excellent dielectric properties: Permittivity ε = 30 and low loss: tan δ= 10-3. FFF can make variations of density for the printed part which makes it possible to print a zirconia part with controlled porosity, and therefore a controlled permittivity lower than 30 and thus reach the optimum value. But the revolution of this process does not stop here: 3D printing allows the creation of ceramic parts with different areas having different densities, and therefore different equivalent permittivities.
Figure above: view of the proposed structure
Parts were printed by Nanoe using Zetamix white zirconia filament, with a layer size of 0,1mm, and 2 giroids infills respectively with 25 and 95% density. Parts were then debinded in acetone for 2 hours and sintered at 1450°C in a zetasinter furnace.
These parts were then tested by LEAT in a small anechoic chamber, on a ground plane by adding 2 RF connectors. The resonator was exited in the bandwidth and a full spectrum was acquired by rotating the antenna in the chamber.
First results show a very good efficiency of the DRA, and a diagram that matched quite closely the simulated version.
Moreover it also shows a deviation to higher frequency (2600MHz), which will be adapted by iterations on design of the DRA.
These result will be fully detail at the EUCAP ( European Conference on Antennas and Propagation ) conference in March at Madrid, Spain
Figure above : Simulated Smith chart.
Figure above : Radiation pattern at 2.6 GHz
Zetamix technology enables the production of material with impressive properties for a low investment. Telecommunication is a cutting edge field pushed by an increase of requests from industrials and public, that always need to provide smaller and cheaper solutions. By exploring the shaping possibilities with 3D printing, LEAT is ready to meet the challenge of next generation antennas.