The deal will give Google "a lot of heft," said Jonathan Goldberg, a research analyst at Deutsche Bank. Motorola is among the oldest wireless companies and has a strong and credible patent portfolio, he said. Motorola Mobility has said it owns about 24,500 patents.

'I think it's a big step and I expect there will be a big sigh of relief at Google once this deal closes," said David Mixon, a patent lawyer with Bradley Arant Boult Cummings. "They were outbid in the Nortel patent auctions and that was a consortium led by Microsoft and Apple. They clearly were feeling some pressure."

If Google is targeted by another lawsuit, Motorola's patents will help it broker a settlement and secure a license for Android, Poltorak said. That license would cover Android device makers as well, under the "exhaustion doctrine," he said. "If Google obtains a license for the OS, then everyone else who uses that OS will be licensed as well."

If a company targets a Google partner instead, Google could transfer ownership of some the Motorola patents to that partner temporarily, so it can defend itself with them, Poltorak said.

Not everyone agreed that Motorola's patents will be an effective deterrent, however. Florian Mueller, author of the FOSS Patents blog, noted that Apple has already sued Motorola Mobility for patent infringement. Motorola's patents appear "too weak" to be a deterrent against lawsuits, he wrote in a .