Methods for figuring out the best schools for a particular field of study I am about to graduate in Electrical Engineering and I wanted to pursue graduate studies in a field such as coding theory or software defined and cognitive radio.

But I'm not sure where to find the information needed to decide which school to choose. University rankings won't be specific enough to point out the quality of the research groups of my interest. I was looking for something that would point out volume and relevance of papers and articles published by the Universities' research groups.

I don't need answers on which school is best, but tools to figure this out by myself.
Research groups that are active in a particular field will publish often in those fields.

So, identify conferences* in your field of interest. Look at the technical programs for the last couple of years, and check out the groups that seem to be contributing a lot.

Also, ask professors at your undergrad university who work in related fields.

* Also workshops, large conferences with a few on-topic sessions, journals, etc.