RDA Technology

How to make RDA (Rear Direct Double injection Antenna)
  Firstly we mold the rear case with inserting several metal radiators such as main/sub antennas for LTE, GPS and Bluetooth.
  Secondly we mold again for thin layer of 0.2mm on the surface of the case where the radiators are exposed.
 
Advantages
  Best antenna performance
  - Looking in from the side, the radiators in case are located higher than
    those mounted on the phone body.   
  Cost efficiency
  - Since the rear case have several antennas as a single body.
    (No assembling process necessary for antenna modules.)