Radio control problem (newbie)

[JasperSmith]

Hi all-
I've got a project that I could do with some help with. I'm trying to put together a system whereby a video camera, mounted on a universal joint, always points towards a specific object (a person). Both the camera and the person are able to move freely.

The method I've come up with is this:
The person being videoed wears a small radio tranmitter
The video camera mount has two aerials, insulated from one another and set at, say, 45° angles to the camera direction; 90° to each other
The camera mount uses a servo to move the camera into the correct alignment, so that it is facing the correct way.

Now, most of what I've outlined is available either off the shelf or there are simple circuit diagrams available. However, the bit that I'm getting stuck on is how to send the message to the servo. I think that what I need is an IC that takes two radio signals, compares the strength of the two and then sends a PCM signal out (as that's how the servo is controlled).

I appreciate that I may be well out of my depth here, but I'm sure it's not that complex a thing that I'm trying to do - despite what the employees in Maplins would have me believe... can anyone help me, give me some pointers, or suggest a different way to do this?

BTW - I've decided that GPS isn't the route I want to take - partly for cost reasons, but also because I think my solution is more elegant. Also, the range of the system needn't be great - probably no more than 20m. It would be useful to have some degree of control over the sensitivity of the comparison though.

Thanks
-Jasper