Replacement for AD630 for the purpose of Lock-in Amplification

I am making a lock-in amplifier which works in the megahertz range(500MHz to be exact). AD630 does not work in this range. So can anyone please suggest some IC which does exactly what AD630 does but at a higher frequency range? Or do I have to use some other approach entirely?

I am also attaching a circuit which I am working with (I got it from Instructables).

This is a bit outside my personal experience; BUT I do have a friend who is one of the top engineers at ADI.  I forwarded a link for this page to him and expect he can either suggest a part, or get help from one of his colleagues to do so.  

I did get a response from ADI; they don't have any part that will do what you need.  In fact what you are trying to do, it seems, is trying to "scale up" a design the was originally intended for high audio range at best.  You simply can't just add 2 or 3 zeros or more to the frequency range of a design!  Sorry to be the bearer of bad news, but that's the reality of RF work.  In the real world, application note circuits aren't even complete real-world designs, just a starting point for a manufacturable circuit that will actually meet the system requirements over all the combinations of temperature range, manufacturing tolerance, component tolerance, etc.  Even construction of a working breadboard isn't proof that the design can be sold in the real world to many different customers!