This would be a difficult subject even for a PhD candidate.
The U.S. Federal Trade Commission held hearings in 2002 and 2003 on the subject of innovation, anti-trust, and IPR laws. The report which they issued should be useful to you:
http://www.ftc.gov/os/2003/10/innovationrpt.pdfNote: The FTC's primary interest is anti-competitive behaviour, not necessarily innovation. In addition to the report itself, it may be interesting for you to read the testimony given during the public hearings:
http://www.ftc.gov/opp/intellect/index.htmAnother good source are the amici (friends of the court) briefs submitted to the U.S. Supreme Court during the recent Eldred case (where the SCOTUS reviewed the constitutionality of the Sony Bono copyright extension act.)
http://cyber.law.harvard.edu/openlaw/eldredvashcroft/legal.html#amiciDeepak Somaya, an economist at the University of Maryland, has also done some impressive (and relatively unbiased) research into the question.
http://www.rhsmith.umd.edu/lbpp/dsomaya/Personally, I find almost all of the research heavily biased by the political leanings of the researchers. The anti-private property left argue that patents and other IPR hinder innovation, while the pro-private property right argues that IPR fosters innovation.
Try not to take a side and keep your mind open. There are good arguments on both sides worthy of consideration, but understand a lot of what you read is self-serving rhetoric.
Good Luck!
Regards,
Eric Stasik