how to get this Smart Antenna

I used the $40 coupon to purchase a RCA Digital TV Converter box. Model 
DTA800. In the back of the box, there is a "Smart Antenna" connector
socket. 
This socket is very much similar to a Ethernet connector plug socket - 6 
pins RJ11 phone plug. But there is a notch at the top side of the socket.

Can you tell me more about this Smart Antenna connector and how to find
out 
more about this type of antenna? Where to buy it and how much it costs?

Thank you.