Disclosed herein is an implantable electronic device having a housing containing an electrical circuit. The implantable electronic device further includes an antenna assembly coupled to the electrical circuit. The antenna assembly has an antenna with a dielectric antenna body within which an antenna trace is disposed. Portions of the antenna trace are disposed in offset transverse layers in a non-overlapping arrangement, thereby reducing capacitive coupling between the layers of the antenna trace. In certain implementations, the antenna assembly has one or more capacitive features that selectively overlap portions of the antenna trace and facilitate tuning of the antenna.