July, 1968

Copper-plated dielectric waveguide may well be considered for use in lightweight planar arrays, for waveguide components in portable microlink communications equipment, and for lightweight parabolic antenna and feed systems. Although the technique of plating dielectric substrates is not new, recent extensive research extends that work has been reported previously. Here are some of the considerations in fabrication, selection, and use of dielectric waveguides.

Selecting the dielectric

Dielectric substrates for plated-dielectric waveguide components should ideally possess the following characteristics:

  • low dielectric constant (ϵ);
  • low-loss tangent (tan δ);
  • closed-cell structure;
  • lightweight;
  • low cost;
  • machinable to fine surface finishes;
  • operate to 212°F;
  • suitable for electroless copper plating;
  • commercially available in relatively large stock sizes.

Not all of these requirements are obtainable together as many are conflicting. For instance,

  • lightweight vs. closed-cell structure: Below 6 lb/ft3, the substrate is open cell; 8 lb/ft3 is closed cell.
  • lightweight vs. machinability to fine surface finishes. The heavier the material the finer the surface finish.
  • lightweight vs. electroless copper plating. The lighter the weight, the coarser the surface finish—thus, the coarser the plated surface.
  • lightweight vs. open-cell structure. These are compatible but are not suitable for high-temperature operation.

A characteristic comparison of four typical substrates investigated is shown in Fig. 1. For copper-plated dielectric waveguide applications, Polystyrene 4 lb/ft3 (commercial) appeared most suitable.

Download this article in .PDF format
This file type includes high resolution graphics and schematics when applicapable.