The antenna are located on the bottom of the iPhone 5. They appear to be part of the lightning connector assembly.
In this image you can see where the ifixit tech is removing the antenna connector from the logic board: http://guide-images.ifixit.net/igi/cI1Rn...
Here is a picture of the lightning connector assembly. You can see the antenna cable hanging: http://guide-images.ifixit.net/igi/n4yuS...
Check out the complete iPhone 5 disassembly by ifixit: iPhone 5 Teardown
I'm thinking the Wi-Fi antenna claimed on step 21 of iPhone 5 teardown would be wrong. (iPhone 5 Teardown) There's already another guide telling where the Wi-Fi antenna is: iPhone 5 Wi-Fi Antenna Replacement
The Murata Wi-Fi module is far from the speaker so this coaxial connector attached with the speaker module should belong to mobile phone functions.
My two cents.