A trace antenna is an antenna made out of a small strip of copper wire on the PCB which just happens to resonate at certain frequencies. This could be intentional, like an F antenna design for 2.4 ...

Waveguides come to mind, but so do active elements like filters made from nothing but PCB traces ... a better explanation of design details such as via stitching and trace finish selection ...

No user-serviceable parts inside? Give me a break! The head unit is tough to get to, but the PCBs within the chassis use ...