Coates, 30, was one of the NFL's top tight ends of the past decade, grabbing 490 passes in nine years and making five Pro Bowls for the New England Patriots.
Coates will enter training camp as the Ravens' back-up behind Sharpe, but the two will play together when the team goes to a two-tight end set.
"Strictly from a football standpoint, the aspect of having two players the caliber of a Shannon Sharpe and a Ben Coates on either side of the center, (creates) a dynamic for the defense that's going to be interesting to see," coach Brian Billick said. "We're excited about it, and I'm excited that we were able to get this done so that he can be in camp and we start this right from the get-go."
The Ravens have been without much of a presence at tight end during their first four years, including just 34 receptions for 251 yards and one touchdown from the position last season.
They made an immediate upgrade when they signed Sharpe, a seven-time Pro Bowler, in February. With the addition of Coates, the Ravens have gone from having no tight ends to having two who were the best at their positions for most of the 1990s.
Coates, who turns 31 in August, is fifth all-time in receptions by a tight end with 490, seventh in receiving yards with 5,471 and third in touchdowns with 50.
However, he had his worst season as a starter in 1999 as the Patriots offense began favoring wide receivers in their passing game. Coates started 15 of 16 games but finished with just 32 catches for 370 yards and two touchdowns.
Coates visited Washington, Detroit and Tennessee before signing with the Ravens. He also considered re-signing with New England but decided against it because of the direction the Patriots were headed under new head coach Bill Bellichick.
"They were doing the rebuilding stage and I don't want to go through the rebuilding stages," Coates said. "This organization wants to win. They want a chance to et to the Super Bowl."
Coates also said he's prepared for a reserve role after being a starter since 1993.
"Shannon is the starter and my role is to be the back-up to spell him and we're going to go to training camp and work on that," Coates said. "Every year you go to training camp and you go in to prove yourself and that you're not done. I want to continue to play and I want to win."
The Ravens, who finished 8-8 last season, begin training camp at Western Maryland College on Sunday.
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