The Fortigate 60D does NOT have a built-in WiFi radio.
The FortiWifi 60D does.
But...
any Fortigate or FortiWifi can act as a wireless controller. This feature is built-in in FortiOS.
If you don't see the menu item 'Wireless controller' in the GUI you first have to enable it. In v5, go to System>Config>Features and enable it. Then you are able to configure external access points from Fortinet which are connected via LAN to the Fortigate.
Sorry, I am a little confused by your question, so let's see if any of these answers satisfy...
Fortinet sells a FortiWifi 60D, that has wifi built-in (one radio, a/b/g/n on either the 2.4 or the 5Ghz range)
The FortiGate 60D (non-wireless) can act as a wireless controller for other Fortinet WAPs and FortiWifi's (it can only manage a certain quantity, unfortunately I don't have those numbers at my fingertips).
The FortiWifi 60D can also manage other WAPs and FortiWifi's while also offering its own wireless.