I would say that they are indeed different people. Ananias and Sapphira are mentioned in Acts chapter 5. The other Ananias is mentioned in Acts chapter 9 which I would think is at a later time.
Although, When the Lord told Ananias to go to Saul, Ananias questioned the Lord (Acts 9:11-15) which is similarto the behavior exhibited by the Ananias who was married to Saphira and lied "...not unto men, but unto God." Acts 5:4