This document discusses, among other things, an implantable dielectric compartment including a channel in an outer surface of the implantable dielectric compartment, the channel configured to constrain a portion of an implantable antenna in a specific configuration along the length of the portion of the implantable antenna. In certain examples, the implantable antenna can be configured to wirelessly transfer information electromagnetically at a specified operating frequency provided using the specific configuration of the portion of the implantable antenna.