Bind radio button to json value

I've MVC application with 3 (it can be also two radio...) radio buttons rb1 &rb2&rb3 which should be bound to screen property in the JSON,one for "fullScreen" and the second "popup" and third to "preview"(in this case I cannot use check-box....)

I need to bind it to the JSON data file the for the same property,how should I do that ?

var con = {

  screen: "fullSceen"

  };

for example if user choose on the rb1 the JSON file will be "fullScreen" if user choose rb2 it will be "popup" and if he choose 3 "preview"

something like enum with 3 values,how should I handle it?

Since I new to UI5 Example will be very helpful:)

Thanks!