Advanced Design of Microwave Components using Shape Optimization and Ceramic Stereo-lithography
Baillargeat, D.¹; Delhote, N.¹; Khalil, H.¹; Aubourg, M.¹; Bila, S.¹; Verdeyme, S.¹; Puech, J.²; Lapierre, L.²; Delage, C.³; Chartier, T.^4
1XLIM; ²CNES; ³CTTC; ⁴SPCTS

The design of advanced components for space and terrestrial telecommunications requires both sophisticated design methodologies and manufacturing technologies for improving current components performances. The challenge is to design integrated high-performance components while using low-cost manufacturing processes.

The current paper reports on technologies and design methodologies intended to surpass conventional approaches.

Stereo-lithography and micro-stereo-lithography are rapid prototyping processes based on a space-resolved laser polymerization. Ceramic suspensions can be used together with these processes for prototyping complex microwave components. A thin layer of ceramic suspension is deposited, hardened in the defined cross sectional pattern and bonded to the previous layer by laser polymerization. The process is repeated until the final object is entirely built. The non-polymerized liquid is finally removed, liberating the solid ceramic object.

Original microwave components (waveguides, resonators, filters...) have been fabricated using these processes [1, 2] from some GHz up to 180 GHz. On the other hand, shape optimization is a suitable approach for generating new components. Several approaches have been developed in the context of computer aided-design (CAD), and some of them can be adapted to electromagnetic inverse problems. Considering an initial object embedded in a more global domain, the more general approach consists in optimising the topology of the object by removing or adding material very locally. In particular, the topology gradient approach [3] is applicable in 2 dimensions for optimising the distribution of metal upon the surface of a planar component or in 3 dimensions for optimising the distribution of dielectric (ceramic) material.

Several components designed and manufactured using these techniques have been tested, providing original solutions for the design of microwave components.

[1] N.Delhote et al, Ceramic layer-by-layer stereolithography for the manufacturing of 3D millimetre-wave filters, IEEE Trans. on MTT, Vol. 55 (3), pp 548-554, March 2007.
[2] C.Duterte et al, 3D ceramic microstereolithography applied to submilliter devices manufacturing, European Microwave Conference, Conference Prodeedings, pp 814-817, October 2007.
[3] H.Khalil et al, Topology optimization applied to the design of a dual-mode filter including a dielectric resonator, IEEE MTT-S, International Microwave Symposium 2008, accepted to be published.