NTP Inc., the patent-owning entity that got $612 million out of a suit against BlackBerry maker Research in Motion Ltd., has hit the nation’s top four wireless carriers with similar lawsuits.

The cases, filed Sept. 7 in the federal district court in Richmond, Va., contend that the carriers infringe on eight patents related to wireless e-mail that were granted between 1995 and 2001 to Thomas Campana, whose inventions became NTP’s portfolio. The defendants are AT&T Inc., Deutsche Telekom AG’s T-Mobile USA, Sprint Nextel Corp. and Verizon Wireless, a joint venture of Verizon Communications Inc. and Vodafone Group PLC.